Microscopical and serological diagnosis of Wuchereria bancrofti

Venous blood from 292 patients attending a Filaria Clinic in Georgetown, Guyana, was assayed by ELISA for IgG and IgM antibodies and by Indirect Haemagglutination Antibody Assay (IHA) against filaria parasites. They were also assayed by microscopic methods before and after concentration procedures for microfilaraemia. Of the 41 blood samples microscopically positive for Wuchereria bancrofti microfilariae, 87.8% (ELISA IgG), 65.9% (ELISA IgM) and 73.2% (IHA) occurred in samples with sub-diagnostic serological threshold titres of < 1:32 (IgG and IgM) and < 1:128 (IHA). But indicators of value based on the standards of the presence of chronic and acute symptoms, the IgG and IgM diagnostic data gave 79.9% sensitivity, 96.4% specificity, 97.1% positive predictable value and 44.3% negative predictive value. A membrane filtration system (92.7%) was slightly better than a centrifugation technique (90.2%), but more efficient than a thick smear preparation (75.6%) for the detection of microfilariae. The filtration system was vastly superior for yields of microfilariae. However, the Knott's concentration (sedimentation) was the most economical in terms of technician time and materials. Most microscopically confirmed filaria cases were in the 20-29-year age group (25%), followed by the broad 30-69-year age groups (10-12%). Males were significantly more commonly affected by the ratio 24.2:6.0. It is recommended that skills and materials for concentration of microfilariae from peripheral blood be maintained in all Caribbean countries. In known filaria endemic countries, it is recommended that the serological tool be used as an aid in diagnosis for patients with acute and chronic symptoms.