Diagnostics is a sea: it’s time to navigate into it
I fully agree with Christian and Lise Lotte Gluud about the need of ensuring by phase I-IV studies that the harms and benefits of new tests are fully understood.
These concepts have been introduced by Alvan Feinstein (1), then underlined by several scientists (2). Nevertheless, I think this model should be applied differently, according to the fields of diagnostics, e.g. biochemistry, microbiology, imaging, pathology, etc.
About microbiology tests, I would like to quote this sentence from a paper by Moons and Grobbee (3): “We believe that evaluation of diagnostic tests on patient outcome is not always necessary. In general, we think that follow up studies are not necessary and the (beneficial) effect of a diagnostic test for patient outcome may be considered as established if (a) diagnostic (cross sectional) studies have shown the test’s ability to detect a particular disease and (b) therapeutic studies provided evidence on efficacy of the management of this disease”.
The above statement could often be applied to testing in infectious diseases, where an effective therapy is prompted by the identification of an aetiological agent.
Sometimes situations are more complicated, e.g. nucleic acid-based tests generally target only a single organism, whereas cultures generally are more broad in coverage, from which the necessity of an impact study on molecular detection of M.tuberculosis (4).
In another case, the long term effect of a test and treat strategy for H.pylori has been compared with endoscopy by a randomised trial, for management of dyspeptic patients in primary care (5).
Moreover, triggering receptor expressed on myeloid cells (TREM-1) in samples of bronchoalveolar-lavage fluid has been studied as a marker of pneumonia in patients receiving mechanical ventilation, following negative results of impact studies on quantitative analysis of cultures of respiratory secretions (6). And so on.
As a convinced student of evidence-based medicine application to clinical laboratory practice, I would like to see an implementation of correct principles of test evaluation, but also more adaptive effort to different branches of diagnostics.
Giuseppe Giocoli MD (retired)
1. Misguided efforts and future challenges for research on “diagnostic tests”. AR Feinstein. J Epidemiol Community Health 2002;56:330–332
2. The evidence base of clinical diagnosis. Knottnerus JA ed. BMJ Books, 2002:1-226
3. Diagnostic studies as multivariable, prediction research. KGM Moons, DE Grobbee. J Epidemiol Community Health 2002;56:337–338
4. Molecular Detection of Mycobacterium tuberculosis: Impact on Patient Care. KL Kaul. Clinical Chemistry 2001;47:1553–8
5. Helicobacter pylori test and eradicate versus prompt endoscopy for management of dyspeptic patients: 6.7 year follow up of a randomised trial. AT Lassen, et al Gut 2004;53:1758–63.
6.Diagnosing Ventilator-Associated Pneumonia. A Torres, and S Ewig, NEJM 2004;350: 433-5
Competing interests: None declared
Competing interests: No competing interests