Can Doctors Make an Accurate Diagnosis of Dengue Infections at an Early Stage

As part of a multi-centre, prospective study of dengue pathophysiology between 1994 -1997, clinical findings and simple laboratory tests were evaluated to find early indicators for the diagnosis of dengue infections so that control actions could be taken as early as possible to prevent the spread of dengue in the community. Six hundred and forty -nine febrile child ren with a flushed face and without signs of localized infection were followed as in-patients. Three hundred and eighteen children were confirmed to have dengue: 176 dengue fever (DF), and 142 dengue haemorrhagic fever (DHF); another 331 children had other , self-limiting febrile illness (OFI). Tourniquet test (TT) positive and leukopenia (WBC ≤ 5,000 cells/cu.mm.) were the two screening tests that helped in the early clinical diagnosis of dengue infections. Studies revealed that TT positive or leukopenia were the two tests that had a high sensitivity of about 90% for the diagnosis of dengue patients, but their specificity and positive predictive value (PPV) were only 50-60% and 60-70% respectively. If the two tests are combined, the sensitivity gets reduc ed to 74% while the specificity and PPV are increased to 85% and 83% respectively. For early, effective and rapid control of dengue outbreak, TT or leukopenia is a good indicator for initiating immediate control measures. TT positive with leukopenia is als o a good indicator for immediate control measures, 83% of this immediate control measures will be necessary but about 26% of dengue cases that have no TT positive with leukopenia will be missed.