Predictive value of thrombocytopaenia in the diagnosis of dengue infection in outpatient settings

Thrombocytopaenia is often relied upon as an important criterion for the diagnosis of dengue infection among patients presenting with an acute non-specific febrile illness. This study was aimed to assess usefulness of thrombocytopaenia in the diagnosis of acute dengue virus infection. This was a clinic based prospective cohort study from May to November 2003. Consecutive patients presenting with acute non-specific febrile illness of less than two weeks were selected from two urban primary care centres. We did full blood count examination (FBC) on the day of visit and dengue serology on day five of illness for all patients enrolled. We repeated the FBC examination for patients who had initial normal platelet counts. Thrombocytopaenia was defined as platelet count < 150 X 10(9)/L. Eighty-seven patients enrolled in the study. Complete data was available for 73 patients. The prevalence of acute dengue virus infection was 27.6%. The sensitivity and specificity were 88% and 71% respectively. The likelihood of acute dengue infection in the presence of thrombocytopaenia was 2.52 and likelihood of not having dengue infection in normal platelet count patients was 5.22. Thrombocytopaenia has fair predictive value in diagnosing acute dengue virus infection. It was more useful to exclude than to diagnose dengue infection.

Study site: Primary Care Centre of Hospital Universiti
Kebangsaan Malaysia (HUKM) and Batu 9 Health Clinic Hulu Langat,