Rapid diagnostic tests for dengue and leptospirosis: antibody detection is insensitive at presentation

OBJECTIVE: To determine the performance of rapid diagnostic tests for dengue and leptospirosis that rely on detecting antibodies that may not be produced when patients present for medical treatment. METHODS: We prospectively enrolled 723 patients with undifferentiated febrile illness presenting to rural hospitals in northern and northeastern Thailand over a 1-year period. We evaluated rapid antibody detection diagnostic tests for dengue and leptospirosis on these patients. RESULTS: Sensitivity of the tests was low at the acute visit (7.6-21.5%). Sensitivity at the convalescent visit ranged from 25.8% to 81.5% and was significantly higher than at the acute visit for all tests (chi(2), P < 0.001). CONCLUSIONS: Low sensitivity of the rapid tests at presentation suggests that their utility in the acute phase of dengue and leptospirosis is limited.