Rates of radiologically confirmed pneumonia as defined by the World Health Organization in Northern Territory Indigenous children

Kerry-Ann F O’Grady, Debbie M Taylor-Thomson, Anne B Chang, Paul J Torzillo, Peter S Morris, Grant A Mackenzie, Gavin R Wheaton, Paul A Bauert, Margaret P De Campo, John F De Campo and Alan R Ruben
Med J Aust 2010; 192 (10): 592-595. || doi: 10.5694/j.1326-5377.2010.tb03644.x
Published online: 17 May 2010


Objective: To determine the burden of hospitalised, radiologically confirmed pneumonia (World Health Organization protocol) in Northern Territory Indigenous children.

Design, setting and participants: Historical, observational study of all hospital admissions for any diagnosis of NT resident Indigenous children, aged between ≥ 29 days and < 5 years, 1 April 1997 to 31 March 2005.

Intervention: All chest radiographs taken during these admissions, regardless of diagnosis, were assessed for pneumonia in accordance with the WHO protocol.

Main outcome measure: The primary outcome was endpoint consolidation (dense fluffy consolidation [alveolar infiltrate] of a portion of a lobe or the entire lung) present on a chest radiograph within 3 days of hospitalisation.

Results: We analysed data on 24 115 hospitalised episodes of care for 9492 children and 13 683 chest radiographs. The average annual cumulative incidence of endpoint consolidation was 26.6 per 1000 population per year (95% CI, 25.3–27.9); 57.5 per 1000 per year in infants aged 1–11 months, 38.3 per 1000 per year in those aged 12–23 months, and 13.3 per 1000 per year in those aged 24–59 months. In all age groups, rates of endpoint consolidation in children in the arid southern region of NT were about twice that of children in the tropical northern region.

Conclusion: The rates of severe pneumonia in hospitalised NT Indigenous children are among the highest reported in the world. Reducing this unacceptable burden of disease should be a national health priority.

Acute lower respiratory infections and pneumonia are major causes of morbidity in Indigenous children,1,2 but systematically evaluated data on the burden of these diseases are lacking. Most studies of disease resulting in hospitalisation have relied on hospital discharge diagnosis codes, which may be influenced by changes in clinician practices and coding procedures over time.

In 2001, the World Health Organization published guidelines for the standardised measurement in research of radiologically apparent pneumonia in children.3 These guidelines are now the benchmark on which burden of disease and intervention studies are based.

According to the WHO protocol, radiologically confirmed pneumonia — endpoint consolidation — is defined as “dense opacity . . . fluffy consolidation of a portion or whole of a lobe or of the entire lung, often containing air bronchograms and sometimes associated with pleural effusion”.3 We studied the incidence of hospitalised, radiologically confirmed pneumonia in Northern Territory Indigenous children admitted to hospital over an 8-year period.

Radiologically confirmed pneumonia

Overall, in 13 205 episodes of care (54.7%), irrespective of diagnosis, chest x-rays were taken within 3 days; endpoint consolidation was found in 11.6% (1535) of these; film quality was inadequate in 14.0% (1854).

The 1535 episodes of endpoint consolidation occurred in 1211 children with a range of 1–16 episodes per child (one episode, 937 children; two or more episodes, 274 children). Median age at the time of admission was 15 months (range, 1–59 months); 40.8% of episodes were for children aged < 12 months and 23% were for children aged < 6 months. Rates were 1.22 times higher for boys (95% CI, 1.19–1.26; P < 0.001), and 2.1 times higher in children in the southern region of NT (Centre) (95% CI, 1.6–2.8) compared with the Top End (Box 3). The average annual cumulative incidence of endpoint consolidation was 26.6 per 1000 population per year (95% CI, 25.3–27.9); 57.5 per 1000 per year in infants aged 1–11 months, 38.3 per 1000 per year in those aged 12–23 months, and 13.3 per 1000 per year in those aged 24–59 months. Annual rates for each year of the study by age group are shown in Box 4.

Chest x-rays were taken within 3 days of admission in 6852 of the 8518 episodes (80.4%) with any diagnosis in the category, acute lower respiratory infection (ALRI). Film quality was inadequate for determining endpoint consolidation in 1305 (19.0%) episodes with ALRI. Endpoint consolidation was diagnosed in 20.4% of episodes with ICD-defined ALRI (1401/6852); 33.2% with non-viral pneumonia (1178/3551); 40.4% with pneumococcal pneumonia (21/52); 13.8% with influenza (32/232) (of which 3% had a concomitant diagnosis of non-viral pneumonia); and 9.2% with bronchiolitis (226/2455) (of which 43% had a concomitant diagnosis of non-viral pneumonia).

Sixty-four episodes with endpoint consolidation had no respiratory diagnosis recorded (4.2% of endpoint consolidation episodes). There were 258 diagnoses attached to these episodes; 59 (22.9%) were conditions listed under the major diagnostic category of infectious and parasitic diseases (predominantly gastrointestinal infections); 55 (21.3%) were haematological and metabolic disorders; 36 (14.0%) were related to external causes and injury (eg, trauma or near drowning) and 10 (3.9%) were ear diseases. The remainder were scattered across other diagnostic categories. As coding errors cannot be excluded, these episodes were included in the analysis.

There were differing seasonal patterns of endpoint consolidation and other respiratory diagnoses between the NT regions. Episodes of endpoint consolidation were more frequent in the winter and spring months in the Central Australian region of NT; in the Top End region, episodes were more evenly distributed across the year.


We found that the annual incidence of endpoint consolidation in NT children under 5 years of age approximates 3%, and in infants aged under 12 months it is as high as 7%. Differences in study design, case ascertainment, and populations complicate direct comparisons; however, rates of WHO-defined endpoint consolidation in NT children are between three and 25 times higher than found elsewhere. The rates in children aged less than 12 months in the Central Australian region of the NT are the highest reported in the world.

Case ascertainment differences may partially explain the high rates of endpoint consolidation we found. First, the entire NT hospitalised population was included, and hospital access has been improving over the past two decades; and, second, we included remote-living children. Comparable data on children in other disadvantaged populations are from studies in predominantly urban or peri-urban populations; children from rural and remote areas, with substantially less access to health services and with differing risk-factor profiles, would have been missed. These studies are from The Gambia (53.0/1000; aged 1–11 months),5 Philippines (13.5/1000; aged 6 weeks to 23 months),6 Indonesia (8.9/1000; aged 1.5–23 months),7 Chile (5.0/1000; aged 4–23 months),8 Fiji (4.3/1000; aged 1–59 months),9 Uruguay (up to 16.9/1000; aged 0–59 months)10 and South Africa (4.9/1000; aged 1.5–30 months).11 Furthermore, we included all chest x-rays taken within the first 3 days of admission. Studies including only x-rays taken on the day of admission may miss some cases, as clinical pneumonia may precede radiologically confirmed endpoint consolidation.

Indigenous children in the NT may have a different risk factor and health care access profile, predisposing them to infection and hospitalisation. Underlying medical conditions or comorbidities (eg, malnutrition, anaemia and gastrointestinal infections) are common,12,13 and the high prevalence of low-birthweight infants is well documented.14-16 Overcrowding, excessive pneumococci and non-typeable Haemophilus influenzae carriage rates in early infancy,17,18 and repeated infections leading to bronchiectasis and chronic lung disease19,20 may play an important role in disease burden.

The major limitations of our study were its retrospective nature, the inclusion of hospitalised children only, and the use of a specific case definition as the primary outcome. The results should be viewed as an underestimate of the true incidence of disease. Most children with ALRI are treated in the community without a chest x-ray and antibiotic use is high.

Measurement error leading to an overestimation of disease incidence is unlikely. All readers were blinded to the clinical diagnosis associated with each chest x-ray film. While readers might have been influenced by knowing that they were examining x-rays from a high-risk population, the incidence of endpoint consolidation found was lower than that anticipated from a priori estimates based on data from Central Australia.21 Furthermore, the proportion of admitted episodes of care deemed positive for endpoint consolidation (20% of all episodes of ALRI in which a chest x-ray was taken) was similar to that reported in other studies.5,11,22

The rates of pneumonia in Indigenous children hospitalised in the NT are among the highest reported in the world. This is unacceptable in a wealthy country like Australia, and reducing this disease burden should be a national priority. Ongoing surveillance programs incorporating aetiological studies and innovative interventions are urgently required.

  • Kerry-Ann F O’Grady1,2
  • Debbie M Taylor-Thomson1
  • Anne B Chang1
  • Paul J Torzillo4
  • Peter S Morris1,5
  • Grant A Mackenzie6
  • Gavin R Wheaton7
  • Paul A Bauert8
  • Margaret P De Campo9
  • John F De Campo9
  • Alan R Ruben5

  • 1 Menzies School of Health Research, Charles Darwin University, Darwin, NT.
  • 2 School of Population Health and Department of Paediatrics, University of Melbourne, Melbourne, VIC.
  • 3 Vaccine and Immunisation Research Group, Murdoch Childrens Research Institute, Melbourne, VIC.
  • 4 Royal Prince Alfred Hospital, University of Sydney, Sydney, NSW.
  • 5 Northern Territory Clinical School, Flinders University, Darwin, NT.
  • 6 Bacterial Diseases Program, Medical Research Council (UK) Laboratories, Fajara, The Gambia.
  • 7 Department of Clinical Effectiveness, School of Medicine, Faculty of Health Sciences, Flinders University, Adelaide, SA.
  • 8 Royal Darwin Hospital, Darwin, NT.
  • 9 Bond University, Gold Coast, QLD.



We thank Ross Andrews, Joan Cunningham (Menzies School of Health Research); Terry Nolan (University of Melbourne); John Carlin, Suzanna Vidmar (Murdoch Childrens Research Institute); Jane Benson (Johns Hopkins University Hospital); and Kim Mulholland, Tilman Ruff, and Thomas Cherian.

Competing interests:

Wyeth Vaccines provided funding for the study, but had no role in the design, data collection, analysis and interpretation, writing, or publication of the article. Kerry-Ann O’Grady has been a senior research officer on sponsored vaccine trials (GlaxoSmithKline, Wyeth, Merck Sharp & Dohme, MedImmune, and CSL) and a recipient of funds for epidemiological research (GlaxoSmithKline).

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