The indirect hemagglutination (IHA) test done with turkey red cells was applied to 173 serum samples obtained from patients and persons exposed to Wuchereria bancrofti and Brugia malayi in endemic areas of Peninsular Malaysia. A crude extract of adult worms of the rat filaria, Breinlia booliati, was used as the antigen. When a titer of 1:16 was taken as negative, positive IHA test rates in sera from microfilaria-negative persons in endemic areas, microfilaremic cases, and patients with clinical filariasis were 13%, 75%, and 80%, respectively. Results of the IHA test correlated well with results obtained with the indirect fluorescent technique.
Current diagnosis of melioidosis is based on bacterial culture and/or serology which is becoming increasingly useful. An IgM-ELISA using heat-killed whole cells of Pseudomonas pseudomallei was developed and compared with an indirect haemagglutination technique (IHAT) and an indirect immunofluorescent technique(IFAT). The IgM-ELISA using a P:N ratio of > or = 2 had a sensitivity of 91% and a specificity of 96%. All 3 assays were further used in a seroepidemiological survey amongst different groups of patients and healthy individuals. It was found that the IFAT performed better than the IHAT, detecting antibodies to P. pseudomallei in 6% of diabetics, 5% of pyrexics, 8% of pregnant women and 3% of farmers. For the same groups the IgM-ELISA detected antibodies in 1% of pyrexics, 8% of pregnant women and a further 14% of farmers. The IgM-ELISA was found to be sensitive and useful for the serological diagnosis of acute melioidosis.
Interpretation of the indirect hemagglutination test (IHA) for melioidosis in endemic areas is difficult because of the presence of antibodies in apparently healthy individuals. Fifty-three out of 200 healthy blood donors in Malaysia showed positive antibody titers (> or = 1 : 40) against Burkholderia pseudomallei. Seven percent had an IHA titer of 1 : 40, 11% had an IHA titer of 1 : 80 while 8.5% had a titer > or = 1 : 160. Out of 258 sera sent for melioidosis serology, 7% of the patients had an IHA titer of 1 : 40, 9% had an IHA titer of 1 : 80 while 20% had an IHA titer of > or = 1 : 160. If a titer of > or = 1 : 80 is taken as cut off point for positivity, 29% of the patients had positive melioidosis serology. Increasing the positivity threshold may jeopardize the sensitivity of the test. A more specific and sensitive test is needed.