Comparison of ELISA versus conventional methods in diagnosis of microfilariae

Filariasis is a major burden in India in states like Andhra Pradesh. With launching of global filariasis elimination program it has become necessary to use sensitive and accurate methods for diagnosis of filariae as compared to conventional methods. We in this study tried to compare the results of detection of microfilariae with conventional slide methods compared with the ELISA method. 90 samples were collected from those attending the Government General Hospital with signs and symptoms of filariasis they were designated as Group I [Test]. 10 normal serum samples Group II [Normal Controls] and 10 serum samples Group III [Endemic Normal] from normal individuals in the endemic pockets identified by filarial control program officers which were detected smear negative were collected as controls. out of the 90 cases in Group I by the ELISA method it was found that the total numbers of positive cases were 53 and total numbers of negative cases were 37, only 4 cases were found to be positive by the conventional slide method. In Group II normal control samples revealed that all the cases were reported as negative by slide method however by ELISA 7 out of total 10 cases were detected with the antigens and antibodies to micofilariae. The group III had no case detected by conventional slide method as positive but ELISA showed the presence of antigens, antibodies in 7 out of the total 10 cases included in the study. The sensitivity and specificity of ELISA with conventional slide method in all the samples was calculated it was found that Elisa has specificity of 90.24% [CI 76.8 to 97.28%] and specificity of 100 % [CI 93.28 to 100%] the positive predictive value PPV was 92.98%. ELISA is superior in detection of all cases of microfilariae. The conventional methods may not accurately identify microfilariae in all samples therefore it is recommended that ELISA forms an integral part for detecting the presence of microfilariae especially in Endemic areas.