Volume 169 Issue 5

Re-engineering the elective surgical service of a tertiary hospital: a historical controlled trial Gideon A Caplan, Ann Brown, Philip J Crowe, Su-Jen Yap and Shaune Noble MJA 1998; 169: 247-251 For editorial comment, see Hillman Abstract - Introduction - Methods - Patients - Outcome measures - Control group--existing system - Postintervention group--the perioperative system - Operative complications - Statistical analysis - Results - Outcomes - Complications - Patient satisfaction - Discussion - Acknowledgements - References - Authors' details - Figure 1 - Figure 2 - - - ©MJA1998 Abstract Objective: To study the clinical effects of re-engineering the processes associated with elective surgery. Design: A prospective, historical controlled trial. Control patients were enrolled from March 1995 to January 1996, and postintervention patients from February 1996 to October 1996. Setting: A major teaching, tertiary care hospital (Prince of Wales Hospital, Sydney). Patients: 224 patients (123 before and 101 after the intervention) undergoing elective herniorrhaphy or laparoscopic cholecystectomy who lived in the local area. Intervention: Introduction of a re-engineered surgical service consisting of preadmission assessment and education, admission on day of surgery, and postacute care after discharge. There were no changes to the operative methods or infection control procedures. Main outcome measures: Length of stay, operative complications, pain scores and patient satisfaction. Results: The risk of a patient suffering one or more complications was reduced in the postintervention group (postintervention v. control patients: 25.7% v. 38.2%; relative risk [RR], 0.66; 95% confidence interval [CI], 0.44-0.98; P = 0.035) because of a reduced risk of wound infections (5.0% v. 16.3%; RR, 0.30; 95% CI, 0.12-0.78; P = 0.0075). Other complications (perioperative or postoperative) and pain scores were unchanged. Patients treated by the re-engineered service had a significantly shorter length of stay, reported a higher level of satisfaction with the preoperative and postdischarge care, and were more likely to say that they would have the same treatment again (92.9% v 82.6%; P = 0.037). Conclusions: Re-engineering surgical services, with an associated reduction in length of stay, does not lead to a deterioration in care and may decrease postoperative complications and increase patient satisfaction. MJA 1998; 169: 247-251 Introduction Financial pressures from insurance companies1 and governments2 are driving changes in the healthcare systems of many countries. One of the most visible changes is shorter hospital stay, especially for elective surgery.3 Organisational changes include preadmission clinics, enhanced patient education, increased use of day surgery, improved discharge planning and postacute care at home; and clinical changes include less invasive surgical techniques and improved anaesthetic drugs.4 The introduction of a package of these organisational changes amounts to a re-engineering of elective surgery.5Many of these changes have been introduced with little scientific evaluation of their effect on patients, and perceptions of detrimental effects on patient care can make such changes unpopular.1,2 Studies of healthcare changes so far6-10 have focused on changes in surgical procedures and have been unable to identify any clinical effects of initiatives, such as preadmission clinics, patient education, reduction in length of stay, and postacute care. Moreover, in these studies, control patients underwent different procedures,6,7 significant results were not obtained,8,9 or there were worse outcomes in the postintervention group.10 We studied the effects of re-engineering our elective surgical service using a prospective, historical, controlled trial. Our re-engineered service comprised a perioperative unit, preadmission anaesthetic assessment based on self-reported questionnaires, admission on the day of surgery, enhanced patient education, use of clinical pathways, and postacute care (Box 1). 1: A re-engineered surgical service Admission coordinated by Perioperative Unit, which sends out, receives and reviews patients' self-reported health questionnaires, and arranges preadmission assessment, if indicated. Patients admitted to Perioperative Unit on day of surgery. After surgery, day-only patients return to Perioperative Unit, others to the ward. Patient information specific for each operation distributed by the surgeon. Nurses reinforce patients' knowledge. Clinical pathways followed. These provide a diagnosis-specific plan for the episode of care and the role of each member of the multidisciplinary team. Postacute care continues at home after discharge, if required. Methods Patients To minimise variation and ensure adequate patient numbers, we studied prospectively a cohort of patients having one of two general surgical procedures (inguinal herniorrhaphy and laparoscopic cholecystectomy). Patients in the control group were treated before and compared with patients treated after the new elective surgical service was commissioned. Patients who lived outside the local area or were admitted as an emergency were excluded. All patients gave informed consent, and the study was approved by the South Eastern Sydney Area Health Service (Eastern Branch) Ethics Committee. Outcome measures Information collected for comparing the control and postintervention groups included length of hospital stay, level of pain (assessed by a linear analogue pain scale), complications of the operation, and patient satisfaction (assessed by a self-reported questionnaire). Control group -- existing system Patients booked for surgery from the surgeon's rooms or surgical outpatients clinic; Patient information and education provided according to individual surgeon's protocols; Patients admitted to the ward on the day before the procedure, clerked by the surgical intern and assessed by the anaesthetist; Postsurgical care given in the surgical ward; and Discharge plans made by ward staff, subject to individual surgeon's decision. A total of 123 control patients were enrolled prospectively from March 1995. (We had planned to enrol 100, but a delay in commissioning the new system extended the enrolment period.) Eligible patients booked for surgery each day were visited by the study nurse on admission to the ward. After surgery, the nurse obtained patient data, including a pain score on Day 1 after the operation, and arranged to contact the patient by telephone on Day 7. Before discharge, patients were given an anonymous, self-reported patient satisfaction survey, based on the Australian model.11 They were asked to rate their overall treatment, the information provided, preoperative treatment, the operation and care after discharge from hospital on a five-point Likert scale from "very satisfactory" to "very unsatisfactory". They were also asked whether they would have the procedure the same way again, and were given a further copy of the pain scale, and asked to complete both documents on Day 7 after the operation and return them in the prepaid envelope provided. The telephone call on Day 7 reminded patients to return their satisfaction surveys and pain scores. Postintervention group -- the perioperative system A more coordinated system was developed, based on the perioperative system (Box 1).12 The surgeons, nursing staff, operating theatre location and organisation and infection control practices did not change. Although surgical registrars changed surgical units during the study period, they worked with other surgeons whose patients were also studied. The Perioperative Unit included a preadmission anaesthetic clinic where patient health questionnaires were completed, and patients with significant comorbidity were fully assessed. Based on the information provided by the questionnaires, 70% of elective surgery patients were seen by an anaesthetist for the first time on the day of surgery, 15% of patients were seen as outpatients before the day of surgery because of anaesthetist preference, and the remaining 15% required further anaesthetic consultation and one (usually) additional outpatient visit for review. All patients, both day-only and those transferring to the surgical ward after the operation, went to theatre from a day-surgery ward within the Perioperative Unit. Patient care was guided by a clinical pathway developed by the multidisciplinary team to drive and support the system. The role of every member of the multidisciplinary team is specified for each day, with alternative plans available if a patient's condition changes. Improved patient educational material was developed for distribution by the surgeons, and patients' comprehension of the material was reviewed by the study nurse at the preadmission anaesthetic clinic or on the day of surgery. If doubts existed about the safety and suitability of a patient's accommodation for postsurgical recovery, the study nurse made a preadmission home visit. After surgery, study patients were transferred to the surgical ward and an existing postacute care service arranged early discharge with follow-up at home. The new system was introduced at the end of January 1996 and enrolment of the 101 patients in the postintervention group commenced in February 1996. A pain scale was completed on Day 1 after operation. The timing of discharge was entirely at the surgeons' discretion, and the study nurse arranged to visit the patient at home within 24 hours of hospital discharge to assess pain control, wound care needs and general postsurgical progress. This visit generally lasted less than half an hour, and occasional further visits were arranged, as clinically indicated. A contact phone number was provided for use in the event of any complications or concerns. Patients in the postintervention group were also asked to complete the self-reported patient satisfaction survey. Operative complications Data on all complications were collected prospectively and crosschecked with the patients' clinical records. The criteria for wound infections were those of the Centers for Disease Control and Prevention (CDC),13 notably that the infection involves only the skin and subcutaneous tissue of the incision, and at least one of the following: purulent drainage from the superficial incision; organisms isolated from aseptically obtained culture of fluid or tissue from the superficial incision; at least one of the following signs or symptoms of infection -- pain or tenderness; localised swelling; redness or heat; and superficial incision is deliberately opened by the surgeon, unless incision is culture negative; diagnosis of superficial incisional surgical site infection by the surgeon or attending physician. Statistical analysis Statistical calculations were performed using SPSS for Windows.14 Normally distributed continuous variables were compared by t tests, dichotomous variables by χ2 tests. Ordinal variables were compared with the Mann-Whitney U test. Logistic regression was used to obtain a multivariate analysis of factors predictive of wound infection. Results From March 1995 to October 1996, 224 patients were enrolled in the study. Baseline characteristics of the two groups were not statistically significantly different (Box 2). 2: Baseline characteristics of elective surgery patients Postintervention group* (n = 101) Control group* (n = 123) Laparoscopic cholecystectomy 57 (56.4%) 65 (52.8%) Herniorrhaphy 44 (43.6%) 58 (47.2%) Mean time in operating theatre (min, SEM) 100.3 (4.2) 102.1 (3.5) Female : male ratio 46 : 55 54 : 69 Mean age (range) (years) 54.4 (21-85) 54.0 (18-90) Smoker 27 (26.7%) 25 (20.3%) Ischaemic heart disease 8 (7.9%) 9 (7.3%) Requires an interpreter 8 (7.9%) 4 (3.3%) Lives alone 19 (18.8%) 23 (18.7%) Lives upstairs (no lift) 37 (36.6%) 39 (31.7%) *Differences were not statistically significant Outcomes The postintervention group had a significantly shorter length of stay, but there was no difference in pain scores between the two groups (Box 3). 3: Outcomes in the postintervention and control groups Outcome Postintervention group Control group Mean length of stay in days (range) 2.2 (1-8) 3.2 (1-9)* For herniorrhaphy 1.8 (1-4) 3.1 (2-7)þ For laparoscopic cholecystectomy 2.5 (1-8) 3.3 (1-9)§ Postoperative pain score mean (SEM) Day 1 21.7 (1.2) 22.6 (0.9) Day 7 9.4 (1.1) 8.4 (1.0) Number of deaths 0 1 (0.8%) Number readmitted 5 (5.0%) 4 (3.3%) Postintervention v. control group: *P < 0.001; þ P < 0.001; § P = 0.020. Complications The postintervention group had a lower risk of suffering any complication (complications in postintervention v. control patients -- 26 [25.7%] v. 48 [38.2%]; relative risk [RR], 0.66; 95% confidence interval [CI], 0.44-0.98; P = 0.035) because of a lower risk of wound infection (Figure 1). There was no significant difference between postintervention and control patients in intraoperative complications or other postoperative complications (Figure 1). Figure 1: Proportion of patients with each type of complication in the postintervention and control groups, including relative risk (RR) and 95% confidence interval (CI) for comparison between the groups. Intraoperative complications were bile/stone spillage (4 v. 5), conversion to open cholecystectomy (4 v. 1) and, in the control group, one each of cystic duct damaged, cystic artery damaged, unsuccessful exploration of common bile duct, local anaesthetic converted to general anaesthetic, penis injured by towel clips, and aspiration into lungs. Postoperative complications are listed in Box 4. Eight patients suffered two complications and one three complications, so that the total for all types of complications exceeds the number of patients who suffered a complication. 4: Postoperative complications Complication Postintervention group (n = 22) Control group (n = 42) Wound infection 5 20 Cerebrovascular accident, died 0 1 ERCP after operation 2 4 Haematoma/haemorrhage/ooze 4 1 Shoulder tip pain 1 2 Scrotal pain or swelling 2 2 Nausea and vomiting 2 0 Constipation (> 4 days) 2 2 Urinary retention requiring indwelling catheter 1 1 Unstable INR after operation, delayed discharge 0 2 Rash (due to antibiotics) 0 1 Fall Day 1 after operation, low blood pressure 0 1 Delirium 0 1 Difficulty mobilising 0 1 Respiratory infection 3 3 ERCP = endoscopic retrograde cholangiopancreatography. INR = International Normalised Ratio. Multivariate analysis using logistic regression found that the only variables significantly predictive of having a wound infection were being in the control group, length of stay (Figure 2) and the patient having a carer (a proxy for functional dependence). Figure 2: Proportion of patients with wound infection in the postintervention and control groups, by length of stay. Patient satisfaction Completed responses to the satisfaction survey were received from 85 postintervention patients (84.2%) and 89 controls (72.4%). Analysis showed that patients in the postintervention group were more satisfied with both the preoperative (P = 0.0094) and the postdischarge treatment (P = 0.0001), as well as the operation, and were also more likely to want to have the procedure done the same way next time, if required (postintervention v. control: 92.9% v 82.6%; difference, 10.3%; 95% CI, 0.8%-19.8%; P = 0.037). There was no difference between the groups in their ratings of the overall treatment or of the information supplied preoperatively. Although the difference in response rates between the control and postintervention groups was significantly different (P < 0.05), there were no significant differences between respondents and non-respondents in terms of age, sex, type of operation, pain scores, complications, comorbidity, living arrangements, occupational or smoking status. Discussion Patients having elective surgery after a re-engineered system of coordinated care for elective surgery was introduced had shorter hospital stays, a lower risk of wound infection and reported higher levels of satisfaction. Previous studies, rather than focusing on the outcomes of the process, as we did, have examined the impact of elements of our re-engineered service (particularly preadmission clinics) on the efficiency of the elective surgical process.15 Our study found a higher rate of wound infection than is generally reported in surgical series, although the rate was within the range of prevalence of nosocomial infections (3%-21%) in a World Health Organization survey,16 and comparable with rates in an Australian survey which also actively followed up patients for wound infections after discharge.17 Surveys may also identify widely varying wound infection rates if different definitions of infections are used.18 Definitions of wound infections which require the presence of pus19 tend to underestimate the true prevalence, given that most doctors institute antibiotic therapy for earlier signs of infection. With decreasing lengths of hospital stay, most wound infections occur after discharge from hospital, where they are often diagnosed and treated by general practitioners (GP) and not surgeons.17 Thus, it is not surprising for series of laparoscopic cholecystectomies to report infection rates which vary from 1% to 17%.6,17 The 70% reduction in the risk of surgical nosocomial infections which we found is relatively large. We used the CDC definition of infection, and found that most infections were diagnosed and treated by GPs before the wounds developed purulent drainage and without waiting for a positive culture result. The study nurses collected the data in the same manner (ie, prospectively during planned follow-up of patients), but the diagnosis of wound infection was left to the treating GP or surgeon. We tested the observation that there is a dose-effect relationship between iatrogenic complications and length of stay in hospital. A relationship between length of stay and risk of nosocomial infection has been observed in a number of studies.18,19 Cruse and foord retrospectively also found that risk of infection increases with length of preoperative stay,19 but previous studies have not prospectively examined the possibility that decreasing the length of stay will result in lower wound infection rates. Our data demonstrate that a reduction in hospital stay as part of a re-engineered surgical service can decrease the wound infection risk. From the near-parallel slope of the lines in Figure 2, it would appear that the difference between the two groups is due to some factor that occurs early in the admission, most likely through decreasing exposure to hospital microbial flora on the night before surgery, resulting in a shift of the curve to the right. Our study design was a prospective, sequential, before-and-after comparison. Randomised controlled trials are generally considered to be the reference standard for evaluating new treatments. However, when the intervention is a coordinated system of care involving a "culture change" in an organisation, there may be a "Hawthorne effect" -- that is, behaviour changes due to an awareness of being in a study -- and leakage of elements of the "culture change" into the control group, thus reducing the power of a randomised controlled trial.20 Our sequential enrolment of patients more closely mimics the situation in hospital when a surgical service is re-engineered, and makes the study results more relevant. Our study had the active collaboration of the hospital administration, and hospital policy was revised at the start of the treatment phase to require all elective surgery patients to be admitted through the Perioperative Unit. The surgeons and operating theatre location and organisation were unchanged, although junior medical staff were rotated. There was no change in antibiotic prophylaxis or hospital infection control policies, thereby minimising any differences in enrolment patterns and other factors between the two arms of the trial. Our patient satisfaction survey suggested that patients were more satisfied with a shorter length of stay combined with the appropriate support after hospital discharge. A previous study in which surgical patients were not similarly supported after early hospital discharge found patients to be less satisfied with the treatment.21 We have demonstrated that changes in the organisation of elective surgery can produce improved health outcomes and patient satisfaction. This does not mean that any reduction in length of stay results in improved outcomes, but that reduced in-hospital support may be replaced with carefully planned and supervised preadmission assessment, education and postdischarge care, without detriment to the quality of patient care. Acknowledgements We would like to acknowledge the invaluable assistance of the staff of Post Acute Care Services, the Perioperative Unit, and the Departments of Surgery and Anaesthetics, without whose help this study would not have been possible. This study was supported by a grant from the Commonwealth Department of Health and Family Services Hospital Access Program. References Sawyer RB. General surgeons in the world of gatekeepers. Am J Surg 1995; 170: 528-531. Maxwell RJ. Why rationing is on the agenda. Br Med Bull 1995; 51: 761-768. Hoare J. Medicine for managers: day surgery. Health Services Management 1992; June: 12-14. Maddern GJ. The changing pattern of surgery [editorial]. Br J Surg 1996; 83: 145-146. Speer TL. With an eye to the future. Hospitals and Health Networks 1996; 70: 43. Barkun JS, Barkun AN, Sampalis JS, et al. Randomised controlled trial of laparoscopic versus mini cholecystectomy. Lancet 1992; 340: 1116-1119. Stoker ME, Vose J, O'Mara P, Maini BS. Laparoscopic cholecystectomy: a clinical and financial analysis of 280 operations. Arch Surg 1992; 127: 589-595. Adler MW, Waller JJ, Creese A, Thorne SC. Randomised controlled trial of early discharge for inguinal hernia and varicose veins. J Epidemiol Community Health 1978; 32: 136-142. Ruckley CV, Cuthbertson C, Fenwick N, et al. Day care after operations for hernia or varicose veins: a controlled trial. Br J Surg 1978; 65: 456-459. Russell IT, Devlin HB, Fell M, et al. Day case surgery for hernias and haemorrhoids: a clinical, social and economic evaluation. Lancet 1977; 1: 844-847. Hill S, Draper M. The role of patient satisfaction surveys in a national approach to hospital quality management. Canberra: AGPS, 1995. Kerridge R, Lee A, Latchford E, et al. The perioperative system: a new approach to managing elective surgery. Anaesth Intens Care 1995; 23: 591-596. Centers for Disease Control and Prevention, US Department of Health and Human Services. National Nosocomial Infections Surveillance Manual. Atlanta, Ga: USDHHS, May 1994. SPSS for Windows [computer program], version 6.0. Chicago: SPSS Inc, 1993. Kahan E, Carel RS, Hart J. Comparison of two pre-admission testing methods for elective surgery patients. Isr J Med Sci 1991; 27: 141-144. Ayliffe GAJ. Surveys of nosocomial infections. Med J Aust 1988; 149: 571-572. Hardy KJ, Miller H, Fletcher DR, et al. An evaluation of laparoscopic versus open cholecystectomy. Med J Aust 1994; 160: 58-62. Freeman J, McGowan JE. Differential risks of nosocomial infection. Am J Med 1981; 70: 915-918. Cruse PJE, foord R. The epidemiology of wound infection: a 10-year prospective study of 62,939 wounds. Surg Clin North Am 1980; 60: 27-40. Bouchet C, Guillemin F, Briancon S. Nonspecific effects in longitudinal studies: impact on quality of life measures. J Clin Epidemiol 1996; 49: 15-20. Michaels JA, Reece-Smith H, Faber RG. Case control study of patient satisfaction with day-case and inpatient inguinal hernia repair. J R Coll Surg Edinb 1992; 37: 99-100. (Received 5 Jun 1997, accepted 18 May 1998) Authors' details Prince of Wales Hospital, Sydney, NSW. Gideon A Caplan, MB BS, FRACP, Director, Post Acute Care Services. Ann Brown, RN, Nurse Manager, Post Acute Care Services. Philip J Crowe, MB BS, FRACS, Surgeon, Department of Surgery. Su-Jen Yap, MB BS, FANZCA, Director, Perioperative Unit, Prince of Wales Hospital. South Eastern Sydney Area Health Service, Sydney, NSW. Shaune Noble, BHA, MPH, Health Services Development Unit. Reprints: Dr GA Caplan, Director, Post Acute Care Services, Prince of Wales Hospital, Randwick, NSW 2031. E-mail: G. CaplanATunsw.edu.au - Readers may print a single copy for personal use. No further reproduction or distribution of the articles should proceed without the permission of the publisher. For permission, contact the Australasian Medical Publishing Company Journalists are welcome to write news stories based on what they read here, but should acknowledge their source as "an article published on the Internet by The Medical Journal of Australia <http://www.mja.com.au>". <URL: http://www.mja.com.au/>

Gideon A Caplan · Ann Brown · Philip J Crowe · Su-Jen Yap · Shaune Noble

Rotavirus infection and rates of hospitalisation for acute gastroenteritis in young children in Australia, 1993-1996 John B Carlin, Patty Chondros, Paul Masendycz, Helen Bugg, Ruth F Bishop and Graeme L Barnes For editorial comment, see Ferson MJA 1998; 169: 252-256 Abstract - Introduction - Methods - Results - Discussion - Acknowledgments - References - Authors' details - Figure 1 - Figure 2 - - - ©MJA1998 Abstract Objective: To determine rates of hospitalisation of young children for acute gastroenteritis in Australia, and to estimate the proportion of these admissions caused by rotavirus infection. Design: Analysis of hospital admission records, and parallel, prospectively collected data on rotavirus-positive admissions. Setting: Hospitals admitting young children in all Australian States and Territories in 1993-1996. Patients: All children under five years admitted to hospital for acute gastroenteritis (International Classification of Diseases, ninth revision principal diagnosis codes 003.0, 004.0-009.3 and 558.9). Main outcome measures: Rate of hospital admission per 1000 children per year by State, and the proportion of admissions caused by rotavirus infection. Results: There were almost 20 000 hospital admissions annually in Australia for acute gastroenteritis in children under five years, at an average rate of 15/1000. An estimated 50% of these were attributable to rotavirus infection, implying a rate of hospitalisation for rotavirus-related gastroenteritis of 7.5/1000/year. Among children under two years this rate was 11.6/1000. Rotavirus incidence rates generally followed a typical seasonal pattern in temperate regions of the country, with sharp peaks in mid to late winter. Rates of hospitalisation varied markedly, even between States with apparently similar patterns of disease, while the incidence in the Northern Territory was 3-5 times higher than other States. Conclusions: Rotavirus-related gastroenteritis is a major cause of hospital admissions in young children, and large savings to the healthcare system are possible if it can be prevented at reasonable cost. Variation in treatment practices between States may be worth studying in greater detail as another source of potential savings. MJA 1998; 169: 252-256 Introduction Rotavirus is a major cause of severe gastroenteritis in young children. Although discovered only 25 years ago,1 the role of this virus in the huge burden of diarrhoeal disease in developing countries was recognised quickly, and in 1985 it was estimated to be responsible for 870 000 deaths annually.2 In developed countries, mortality from gastroenteritis is low, but many studies have documented the large burden of morbidity caused by rotavirus.3-7Precise estimates of rotavirus-related morbidity are difficult to obtain from routine hospital data because stool samples for microbiological testing are not obtained from all children admitted to hospital with diarrhoea. Even when testing is performed, the findings may not be recorded or coded in the medical record. There was no specific category in the International Classification of Diseases, ninth revision (ICD-9-CM) for rotavirus diarrhoea until 1993, and since then the specified code (008.61) has not been used consistently. However, many studies have shown that at least 30% of hospital admissions for acute gastroenteritis in young children are the result of rotavirus infection and, further, that the incidence of rotavirus infection has a distinctive cyclical pattern with a peak in winter (this is unique to rotavirus among all major pathogens associated with gastroenteritis).3,4,6,8-10 While other Australian studies have examined aspects of rotavirus gastroenteritis,5,11 there are no national population-based estimates of the incidence of hospital admission for acute gastroenteritis in young children. Such estimates are important in assessing preventive measures, and in evaluating the cost-effectiveness of rotavirus vaccines currently under development.12,13 We aimed to provide the first national data on rates of hospitalisation of young children for acute gastroenteritis in Australia, and to estimate the proportion of these admissions that could be ascribed to rotavirus infection. Our results will be used in a later study to estimate the cost-effectiveness of rotavirus vaccination. Methods State and Territory health departments provided computer files with unidentified records for the years 1993 through 1996 of all hospital admissions of children under the age of five with a principal diagnosis in the medical record of acute gastroenteritis. In our analysis, we combined data from the Australian Capital Territory with those from New South Wales. Acute gastroenteritis was identified as ICD-9-CM codes in the range 003-009 (covering infectious gastroenteritis of various known and unknown origins) or code 558.9 ("other and unspecified noninfectious gastroenteritis"). This last code was included for consistency with other studies in the expectation that it might comprise a substantial number of cases of infectious gastroenteritis. Similar files of admission records were obtained from participating paediatric hospitals in each of the States (see Box 1). Records from the Royal Children's Hospital (RCH), Melbourne, and Princess Margaret Hospital (PMH), Perth, also included an identifying hospital record number. 1: Participating hospitals Royal Children's Hospital, Melbourne (VIC) Princess Margaret Hospital, Perth (WA) Women's and Children's Hospital, Adelaide (SA) Alice Springs Hospital (NT) Royal Darwin Hospital (NT) Royal Hobart Hospital (TAS) Sydney Children's Hospital (formerly Prince of Wales Children's Hospital) (NSW) New Children's Hospital, Sydney (Royal Alexandra Hospital for Children) (NSW) Westmead Hospital, Sydney (NSW) Royal Brisbane Hospital (QLD) Microbiology departments at participating hospitals were asked to forward all rotavirus-positive faecal specimens obtained from children under five years who were admitted for acute gastroenteritis to laboratories at RCH, where rotavirus infection was confirmed by enzyme immunoassay.14 All participating hospitals provided specimens over the entire study period, except that Westmead Hospital participated in the study for the first two years only, and was replaced by Sydney Children's Hospital in 1995. Seasonal, temporal, and geographic variation in strains of rotaviruses will be reported elsewhere. We estimated the proportion of gastroenteritis admissions that were caused by rotavirus infection both by direct and indirect means. The direct method involved a linked analysis of admissions and rotavirus data. Admission and laboratory records from RCH (Melbourne) and PMH (Perth) were linked by means of hospital unit record number and date of admission/date of specimen, thus identifying the proportion of admissions that we could directly confirm as involving rotavirus infection. This analysis was supplemented with information from each hospital's pathology records, as it became clear that not every rotavirus-positive specimen was being sent on to our laboratory (usually owing to insufficient size of samples). Further, it was possible to omit patients for whom no faecal test was performed, to give a more appropriate denominator for estimating the fraction admitted because of rotavirus infection (calculated as rotavirus fraction = number of admissions with positive rotavirus test result/number of admissions with faecal specimen tested). The indirect statistical estimation of the rotavirus fraction and the rationale behind this method are described in Box 2. The study was approved by ethics committees in each of the participating hospitals. 2: Statistical estimation of the rotavirus fraction We assumed (i) that rotavirus is the only major cause of childhood gastroenteritis admissions that shows significant seasonal variation; and (ii) that the total number of admissions due to rotavirus in a State is a constant multiple of the number seen in our participating hospital(s). Thus, total admissions per month were expressed as the sum of a constant number (representing non-rotavirus causes) and varying numbers of rotavirus admissions. The resulting linear regression model for the number of admissions in a State in each month was used to estimate the rotavirus fraction (the proportion of hospital admissions for acute gastroenteritis resulting from rotavirus infection). This is shown mathematically below, where: Ni = number of acute gastroenteritis admissions in the State in month i; ni = number of "rotavirus-positive" admissions in the State's participating (index) hospital(s); = monthly number of admissions statewide not caused by rotavirus; and = scaling factor relating the number of "rotavirus-positive" admissions in the State to that in the index hospital(s). The regression model (in which i = random error) is: Ni = + ni + i , which leads to: We followed earlier practice4,5 and used ordinary least squares to estimate , despite the fact that the model does not fit the usual assumptions of linear regression (in particular, the variance of i cannot be expected to be constant). As the assumption that there is perfect correlation between rotavirus incidence recorded at the index hospital and total rotavirus numbers at all hospitals in the State is inevitably untrue, there will be an underestimation of in this model, and consequently some underestimation of the rotavirus fraction. On the other hand, if the assumption that rotavirus is the only agent responsible for seasonal variation is wrong, then the estimation may be biased in either direction. The estimate is also potentially subject to other biases relating to the completeness and regularity of coverage of the contributed rotavirus samples. These biases are likely to outweigh random error, so that conventional confidence intervals would not provide a reliable indicator of uncertainty. Results Total numbers and estimated rates of acute gastroenteritis admissions are shown in Box 3. Of all admissions, 65.7% involved children under the age of two years, with approximately equal numbers in each of the first two years of life, and declining numbers in each of the subsequent three years to age five. The age breakdown was similar in all States except the Northern Territory, where a substantially larger proportion were aged under two (86.1%). Length of stay was also considerably longer in the Northern Territory. There were slightly more boys than girls (53.1% overall), consistent across all States. Of all admissions, 29.4% were coded 558.9, although this proportion declined sharply over the four years of the study as coding practices apparently changed. 3: Acute gastroenteritis in children aged less than five years, 1993-1996. Number and rate of hospital admissions, rate ratio relative to the Victorian rate, and average length of stay (95% confidence intervals in parentheses) State or TerritoryAverage annual admissionsAnnual rate per 1000 children under 5 yearsRate ratio relative to VictoriaAnnual rate per 1000 children under 1 yearAnnual rate per 1000 children aged 1-2 yearsAverage length of stay Victoria29159.2 (9.0-9.3)1.00 14.6 (14.1-15.1)14.4 (13.9-14.8) 1.93 days (1.90-1.96) Tasmania3199.3 (8.8-9.8) 1.01 (0.96-1.07) 15.0 (13.6-16.4) 15.1 (13.7-16.6) 1.79 days (1.71-1.87) Western Australia178614.2 (13.9-14.5) 1.55 (1.51-1.60) 25.3 (24.3-26.2) 24.9 (24.0-25.9) 3.13 days (3.03-3.23) Queensland377316.0 (15.7-16.2) 1.74 (1.70-1.79) 24.0 (23.3-24.7) 26.4 (25.6-27.1) 2.15 days (2.11-2.18) New South Wales*786617.1 (16.9-17.3) 1.87 (1.83-1.91) 25.5 (25.0-26.0) 27.5 (27.0-28.1) 2.11 days (2.09-2.13) South Australia189519.2 (18.8-19.7) 2.10 (2.04-2.16) 32.0 (30.7-33.2) 30.7 (29.5-31.9) 2.09 days (2.03-2.15) Northern Territory85449.8 (48.2-51.4) 5.44 (5.24-5.65) 106.2 (101.0-111.3) 108.1 (102.9-113.3) 9.18 days (8.88-9.47) Total1940815.0 (14.9-15.1) 23.9 (23.6-24.2) 25.0 (24.7-25.3) * Including Australian Capital Territory. Box 4 shows the temporal pattern of all admissions and of rotavirus admissions in index hospitals in the five largest States and the Northern Territory. The seasonal peaks in the eastern States (New South Wales, Victoria, Queensland, and South Australia) were generally coincident and occurred regularly in the colder months from July to September (except for the unusual final year in South Australia). In contrast, the weaker and less regular peaks in Western Australia occurred earlier than in the eastern States, and there was no discernible seasonal pattern in the Northern Territory. Even where the seasonal pattern was less distinct, the peaks in statewide admissions were reflected in peaks in the numbers of rotavirus- positive specimens. 4: Monthly incidence of hospital admission for acute gastroenteritis in children under five years of age in Australian mainland States and the Northern Territory, 1993-96 (solid line) and number of rotavirus-positive specimens received from participating hospitals in that State, rescaled from the hospital to the State level (dashed line), by the "regression method" For the data linkage method, among 1732 children admitted for whom a specimen was tested, we received 767 rotavirus-positive specimens from RCH (Melbourne) and found another 205 admissions with hospital records showing a positive rotavirus test, giving an estimated rotavirus fraction of 56%. The corresponding totals from PMH (Perth) were 1631, 626 and 161, respectively, giving a rotavirus fraction of 49%. Regression estimates of the rotavirus fraction ranged from a low of 22% for the Northern Territory (based on a total of 598 rotavirus-positive specimens) to a high of 41% for Victoria (984 specimens). When data from all States were combined, the correlation between rotavirus numbers and admissions increased, because a more accurate representation of the relationship between total admissions and rotavirus numbers in participating hospitals was obtained by pooling. The resulting estimated rotavirus fraction was 50% (based on 4634 specimens received). Separate estimates obtained for children aged under one year, one year to less than two years, and at least two years were 34%, 60% and 48%, respectively. Discussion This national four-year study has shown that there are almost 20 000 hospital admissions annually in Australia for acute gastroenteritis in children aged under five years -- an average rate of 15 per 1000, 50% of which appear to be attributable to rotavirus infection. The annual rate of hospitalisation for rotavirus-related gastroenteritis in children under five is therefore about 7.5 per 1000. Among children under two years, combining estimates for the two one-year age brackets, the corresponding rate is 11.6 per 1000, or just over one in every 100 children. Of the two methods we used to estimate the proportion of admissions that were caused by rotavirus, the method involving direct linkage of hospital admission records and stool specimen tests is likely to be the more accurate. Estimates of 56% (Melbourne) and 49% (Perth) were obtained for the two centres where it was available. These estimates may be too low, as enzyme immunoassay can fail to detect up to 10% of rotavirus-positive specimens.15 Conversely, they might be too high on a population-wide basis, as they were based on tertiary referral centres where the severity of admitted cases -- and therefore the likelihood of rotavirus involvement -- might be higher (although this was only weakly supported by our data on mean length of stay [LOS], which showed a small difference between RCH [mean LOS 1995-1996, 2.15 days] and the whole of Victoria [1.87 days], and no difference between PMH and WA averages [2.80 v. 2.85]). Our second method, based on a regression model, was subject to statistical fluctuations and assumptions that imply it might produce an underestimate of the rotavirus fraction (see Box name="box2"2). In particular, the coverage of rotavirus specimen collection varied between States and also, at times, within States. For example, only a relatively small number of specimens (457) were ascertained from New South Wales, implying that the rotavirus fraction for that State might be considerably underestimated. In fact, when the regression method was applied to the pooled national data, we found reasonable convergence between the two methods, and believe they both support the conclusion that 50% of all gastroenteritis admissions in this age group are due to rotavirus. A reasonable range of possible alternative estimates around this value would be from 40% to 60%. In other studies, estimates of the proportion of hospital admissions in children under five years attributable to rotavirus have ranged from around 30% to as high as 66%.3,4,6,8,9,16 United States studies from the Centers for Disease Control have estimated this proportion both by a simple "residual" method based on assuming that all diarrhoea admissions in the winter seasonal peaks are rotavirus-related,17 and a more direct method based on an eight-year series of children admitted to a Washington DC hospital.6 Both methods indicated that rotavirus was responsible for about one-third of admissions, and the corresponding annual rate of hospitalisation for rotavirus-related gastroenteritis in children under five years was 2.8 per 1000. In the United Kingdom, estimates have been based on laboratory surveillance and hospital discharge data, with a similar statistically based estimation procedure to ours.4 It was found that 43% of admissions in children under five years could be attributed to rotavirus, corresponding to 5.3 per 1000 admissions per year. A New South Wales study by Ferson also used a regression method, based on a larger sample of rotavirus surveillance data than ours, and estimated an annual rate of hospital admission of 8.7 per 1000.5 Using the 1993-1996 NSW hospital admission rates (Box name="box3"3), this corresponds to a rotavirus fraction of 51%, very consistent with our national estimate. Ferson's study found over twice the rate of rotavirus gastroenteritis in the second year of life compared with the first, a slightly greater difference than suggested by our data. The findings of both studies are consistent with a detailed investigation of children with gastroenteritis over 13 years at RCH Melbourne, which found that no pathogen could be identified in a substantially greater proportion of infants under six months than in older children.18 There were substantial differences in hospital admission rates between the States, with NSW, Queensland and South Australia having almost twice the rate of hospitalisation of Victoria. It seems very unlikely that these differences are the result of different disease patterns, especially as the seasonal patterns in these States were very similar. Nor are they likely to be explained by differences in coding, as our incidence figures are based on an inclusive selection of principal diagnosis ICD-9-CM codes. In particular, the inclusion of code 558.9 ("non-infectious gastroenteritis") identified a substantial number of apparently miscoded cases of viral diarrhoea, consistent with findings in other reports.4,5 The differences may reflect variations in patterns of primary care influencing the numbers of children who present to hospital emergency departments, and/or differences in hospital admission policies. The relative importance of each of these factors warrants further study, as it appears likely that substantial savings could be made if hospitalisation rates nationally could be reduced. There were no major seasonal differences in gastroenteritis incidence between States, except in the Northern Territory and Western Australia, where the relative importance of rotavirus in the gastroenteritis disease burden may be somewhat reduced. There is little evidence in our data of a progressive spread of the rotavirus epidemic across the country each year, in the manner that has been described in North America,19 apart from the fact that the annual peak of rotavirus activity in Western Australia appears generally to precede that in the eastern States. The Northern Territory was the most clearly distinct of all the regions, not only in its substantially higher hospital admission rate and lack of seasonal pattern, but also in the dramatically longer length of stay of patients. Average length of stay in this study (2.2 days, excluding the Northern Territory) was substantially shorter than that reported in the United States (3.9 days20), but very similar to British findings.4 Given the higher admission rates in Australia, shorter length of stay may reflect a less severe spectrum of illness, or possibly better management involving more widespread use of oral rehydration solution. Our results imply that 10 000 hospital admissions occur annually in Australia for rotavirus gastroenteritis. The direct cost of this hospital care is at least $12 million, based on an (Australian national diagnosis-related group-based) estimate of $1244 per admission,21 and may be as high as $15-$18 million (preliminary analysis, RCH [Melbourne] costing data). A successful rotavirus vaccine -- depending on its cost -- could result in substantial savings to the healthcare system. Acknowledgments The study was funded by the Public Health Research and Development Committee of the National Health and Medical Research Council. It would not have been possible without the generous cooperation of numerous individuals in all State and Territory health authorities, and in medical records and hospital information units at the participating hospitals, or without the participation and skilled assistance of the following microbiologists and paediatricians: G Davidson, P Goldwater, T Kok, A Lawrence, L Micken, S Weir (Adelaide); G Clift, J Erlich, J Hagger, R Matters, F Morey (Alice Springs); J Faogali, J Farrah, R Shepherd, M Witt (Brisbane); G Lum, A Lowe, A Ruben, B Way, K Withnall (Darwin); A Carmichael, A Claridge, K Dahlenburg, R Fang, R Tucker (Hobart); B Crawford, G Hogg, B Ross, R Schnagl, P Ward (Melbourne); B Dwyer, R Hill, A May, G O Connor, B Wild (Perth); P Amin, T Borg, A Cunningham, J MacRae, P McIntyre, C McIvor, K McPhie, J Mitchell, J Montgomery, G Sandico (Sydney). References Bishop RF, Davidson GP, Holmes IH, Ruck BJ. Virus particles in epithelial cells of duodenal mucosa from children with acute non-bacterial gastroenteritis. Lancet 1973; 2: 1281-1283. Bern C, Glass RI. Impact of diarrheal diseases worldwide. In: Kapikian AZ, editor. Viral infections of the gastrointestinal tract. New York: Marcel Dekker, 1994: 1-26. Glass RI, Kilgore PE, Holman RC, et al. The epidemiology of rotavirus diarrhea in the United States: surveillance and estimates of disease burden. J Infect Dis 1996; 174 (Suppl 1): S5-S11. Ryan MJ, Ramsay M, Brown D, et al. Hospital admissions attributable to rotavirus infection in England and Wales. J Infect Dis 1996; 174 (Suppl 1): S12-S18. Ferson MJ. Hospitalisations for rotavirus gastroenteritis among children under five years of age in New South Wales. Med J Aust 1996; 164: 273-277. Brandt CD, Kim HW, Rodriguez WJ, et al. Pediatric viral gastroenteritis during eight years of study. J Clin Microbiol 1983; 18: 71-78. Matson DO, Estes MK. Impact of rotavirus infection at a large pediatric hospital. J Infect Dis 1990; 162: 598-604. Konno T, Suzuki H, Imai A, et al. A long-term survey of rotavirus infection in Japanese children with acute gastroenteritis. J Infect Dis 1978; 138: 569-576. Spence L, Singer O, Kibsey P, Fauvel M. Rotavirus infection in children with diarrhoea admitted to a general hospital in metro Toronto. Can J Pub Health 1985; 76: 17-20. Lewis HM, Parry JV, Davies HA, et al. A year's experience of the rotavirus syndrome and its association with respiratory illness. Arch Dis Child 1979; 54: 339-346. Liddle JLM, Burgess MA, Gilbert GL, et al. Rotavirus gastroenteritis: impact on young children, their families and the health care system. Med J Aust 1997; 167: 304-307. Smith JC, Haddix AC, Teutsch SM, Glass RI. Cost-effectiveness analysis of a rotavirus immunization program for the United States. Pediatrics 1995; 96: 609-615. Barnes GL, Lund JS, Adams L, et al. Phase 1 trial of a candidate rotavirus vaccine (RV3) derived from a human neonate. J Paediatr Child Health 1997; 33: 300-304. Coulson BS, Unicomb LE, Pitson GA, Bishop RF. Simple and specific enzyme immunoassay using monoclonal antibodies for serotyping human rotaviruses. J Clin Microbiol 1987; 25: 509-515. Husain M, Seth P, Broor S. Detection of group A rotavirus by reverse transcriptase and polymerase chain reaction in feces from children with acute gastroenteritis. Arch Virol 1995; 140: 1225-1233. Donelli G, Ruggeri FM, Tinari A, et al. A three-year diagnostic and epidemiological study on viral infantile diarrhoea in Rome. Epidemiol Infect 1988; 100: 311-320. Ho MS, Glass RI, Pinsky PF, Anderson LJ. Rotavirus as a cause of diarrheal morbidity and mortality in the United States. J Infect Dis 1988; 158: 1112-1116. Barnes GL, Uren E, Stevens KB, Bishop RF. Etiology of acute gastroenteritis in hospitalized children in Melbourne, Australia, from April 1980 to March 1993. J Clin Microbiol 1998; 36: 133-138. LeBaron CW, Lew J, Glass RI, et al. Annual rotavirus epidemic patterns in North America: Results of a 5-year retrospective survey of 88 centers in Canada, Mexico, and the United States. JAMA 1990; 264: 983-988. Jin S, Kilgore PE, Holman RC, et al. Trends in hospitalizations for diarrhea in United States children from 1979 through 1992: estimates of the morbidity associated with rotavirus. Pediatr Infect Dis J 1996; 15: 397-404. Australian casemix report: on hospital activity, 1995-96. Canberra: Department of Health and Family Services, 1997. (Received 30 Oct 1997, accepted 4 May 1998) Authors' details Clinical Epidemiology and Biostatistics Unit, Royal Children's Hospital, Melbourne, VIC. John B Carlin, BSc(Hons), PhD, Deputy Head, and Associate Professor, Department of Paediatrics, University of Melbourne; Patty Chondros, BSc(Hons), Research Assistant. Department of Gastroenterology and Clinical Nutrition, Royal Children's Hospital, Melbourne, VIC. Paul Masendycz, BAppSc, Research Assistant; Helen Bugg, BSc, Research Assistant; Ruth F Bishop, AO, DSc, PhD, Senior Principal Research Fellow (NHMRC, and Professor, Department of Paediatrics, University of Melbourne; Graeme L Barnes, MD, FRACP, Senior Gastroenterologist, and Associate Professor, Department of Paediatrics, University of Melbourne. Reprints: Associate Professor G L Barnes, Department of Gastroenterology and Clinical Nutrition, Royal Children's Hospital, Parkville, VIC 3052. E-mail: barnesgATcryptic.rch.unimelb.edu.au - Readers may print a single copy for personal use. No further reproduction or distribution of the articles should proceed without the permission of the publisher. 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John B Carlin · Patty Chondros · Paul Masendycz · Helen Bugg · Ruth F Bishop · Graeme L Barnes