ORIGINAL ARTICLES
COMMENTARY
Esha Das Gupta FRCP, Department of Internal Medicine, International Medical University
Das Gupta E. Commentary on “Clinical features of acute thrombocytopaenia among patients attending primary care clinics.” Malaysian Family Physician. 2006;1(1):18
Studies that evaluate the utility of clinical history and physical examination was popularised by the JAMA's Rational Clinical Examination series.1 In this series, few authors hail from primary care and relatively few cited papers were conducted in the primary care setting. This is somewhat disturbing. Primary care doctors rely almost entirely on the selective use of history and physical examination to make diagnosis. But, the utility of these clinical skills that are used daily in the diagnostic tasks are inadequately evaluated in the setting where they are used.
It is thus of interest to read this paper by Tong et al who attempted to evaluate the predictive value of history in the detection of thrombocytopaenia among febrile patients.2 The gist of their findings is this: patients with acute febrile illness of unapparent cause in primary care may be having thrombocytopaenia if the fever is of longer duration (≥3 days) or is associated with nausea/vomiting. Although the authors did not verify the aetiology of fever in their patients, it is likely that there were more dengue patients in the thrombocytopaenic group - this is consistent with the longer duration of fever at presentation. What about the association between thrombocytopaenia and nausea/vomiting? Chadwick et al3 did not find a higher prevalence of nausea or vomiting when comparing the serogically proven dengue and non-dengue patients in hospitalised patients. On the other hand, Seet et al4 found that nausea and diarrhoea (but not vomiting) were significantly more common among Chinese immigrant workers who contracted dengue (compared to historical controls).
Even if the gastrointestinal symptoms noted in this study were causally related to dengue infection, I am doubtful if nausea/vomiting per se is useful as a diagnostic aid in clinical practice. This is because both symptoms are rather ill-defined and can occur in a wide variety of febrile illnesses, many of which are not even primarily gastrointestinal diseases or clinically serious. In fact, in a diagnostic study searching for the predictors of streptococcal tonsillitis, Kreher et al5 found that nausea and vomiting are somewhat more common in streptococcal than non-streptococcal tonsillitis. In our search for clinical predictors, we need to bear in mind that a red herring may be found instead. Another point to note: in diagnostic study it is useful to report the performance of the diagnostic test (e.g. sensitivity, predictive values, etc).6 In spite of the statistical significance obtained, the test item evaluated may not achieve a respectable level in terms of the test performance.
REFERENCE
- Sackett DL. The rational clinical examination. A primer on the precision and accuracy of the clinical examination. JAMA. 1992 May;267(19):2638-44 [PubMed]
- Tong SF, Noorazah AA, Chin GL, Khairani O. Clinical features of acute febrile thrombocytopaenia among patients attending primary care clinics. Malaysian Family Physician. 2006;1(1):15-17
- Chadwick D, Arch B, Wilder-Smith A, Paton N. Distinguishing dengue fever from other infections on the basis of simple clinical and laboratory features: Application of logistic regression analysis. J Clin Virol. 2006 Feb;35(2):147-53 [PubMed]
- Seet RC, Ooi EE, Wong HB, Paton NI. An outbreak of primary dengue infection among migrant Chinese workers in Singapore characterized by prominent gastrointestinal symptoms and a high proportion of symptomatic cases. J Clin Virol. 2005 Aug;33(4):336-40 [PubMed]
- Kreher NE, Hickner JM, Barry HC, Messimer SR. Do gastrointestinal symptoms accompanying sore throat predict streptococcal pharyngitis? An UPRNet study. Upper Peninsula Research Network. J Fam Pract. 1998 Feb;46(2):159-64 [PubMed]
- Espallardo NL. Decisions on diagnosis in family practice: Use of sensitivity, specificity, predictive values and likelihood ratios. Asia Pacific Family Medicine. 2003;2:229-32 [Full text]