Ambitious guide to diagnostic tests | |
Pocket guide to diagnostic tests. Australian edition. Robert Dunstan, Diana Nicol, Stephen J McPhee, et al (editors). Sydney: McGraw-Hill, 2003 (viii + 488 pp). ISBN 0 074 710362. |
The concept of a pocket guide
to assist clinicians in their choice of diagnostic tests is an excellent one — unfortunately, here, the authors have set themselves too ambitious a task.
If they had limited themselves to common laboratory tests for common diseases they would have fulfilled their intent. This edition is described as "especially adapted for the Australasian market", but the adaptation is not comprehensive and the manual remains very North American in its perspective. In addition, where costs are mentioned, it is unclear whether they are quoting Australian dollars, and whether the costs are based on test performance or cost to the patient. The quantity and quality of the information varies widely. The chapter on basic principles and interpretation of test results provides sections on patient preparation, specimen collection and interfering factors, which are extremely useful. However, the section on reference intervals mars this chapter, as these are often population and method specific, and those in the book should only be used as a guide. Much of the remaining information is too detailed and technical to be of real use to busy clinicians. Many of the "common bedside laboratory procedures" described are not easily performed at the bedside. For example, the Gram stain for microbiological assessments and Wright stain for examination of the peripheral blood require considerable expertise both in performance and interpretation. At the same time, some common procedures which could be conducted under these circumstances, such as measuring blood glucose, cholesterol and haemoglobin levels, are not mentioned. Some instructions are clearly wrong — tubes should not be filled "completely", but rather to the specified level; and glass tubes are no longer used when measuring arterial blood gases. Also, no mention was made of evacuated blood sample containers, which are in almost universal use in Australia. Similarly, many of the examples of "commonly used laboratory tests" described in chapter three are not "common", and to label them as such is misleading and may lead to overordering. Several of the references in the "Comments" column in this chapter are too old to be useful, with some dating as far back as 1967, and many being from the 1980s. All references to blood banking quote the 13th edition of the Technical manual of the American blood banks, whereas the 14th edition is the current benchmark. Calculations for low-density lipoprotein (LDL) cholesterol are only given for conventional units, not for SI units, and the glucose tolerance test uses United States protocols and not World Health Organization or Australian guidelines. While there are many drawbacks in the chapter, many of the tests, together with interpretation and comments, are well presented and could be useful for reference purposes. The excellent introduction to therapeutic drug monitoring is clearly set out with all the requisite information, including half-life and requirements for dosage adjustment. There is microbiological information about "clinically important diseases", but again some very uncommon situations are described. The categorisation by body area is commendable and useful. The authors do make some helpful introductory comments relating to medical imaging in chapter six; however, this chapter is quite inadequate, with insufficient information to be of real value. For instance, indications for CT scan of the brain are restricted to intracranial or subdural haemorrhage, and there is no mention of space-occupying lesions, thrombotic events or hydrocephalus. There is no apparent correlation between chapters, as abdominal imaging makes no reference to imaging for diverticulitis, which is recommended in the microbiology chapter. The chapter on basic electrocardiography is more comprehensive and, overall, is useful. It could be the basis for an excellent small pocket guide in its own right. The final chapter provides algorithms, nomograms and tables and is a mixture of useful and less useful facts, figures, interpretations and recommendations. The layout is complicated and difficult to negotiate. In summary, this book cannot be recommended as a quick, reliable and easily portable reference for investigating clinical problems in the Australian setting. Eva Raik
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