A Comparative Study of IgM Capture ELISA and Particle Agglutination Assay for the Diagnosis of Japanese Encephalitis among Nepalese Patients

Abstract

Japanese encephalitis (JE) is one of the serious public health problems particularly in the Terai regions of Nepal. At present, diagnosis of JE in Nepal is particularly based in the clinical diagnosis. Laboratory diagnosis is made with IgM-capture ELISA in few referral centres, which require sophisticated equipment, costly and time consuming. Recently, a simple particle agglutination assay (PA) had been developed to diagnose JE, which can be done anywhere, does not require sophisticated equipment and can be done at room temperature. This study was conducted to evaluate the particle agglutination assay as a diagnostic method to detect anti-JEV antibodies in human serum samples. In the study, a total of 279 serum samples were collected. PA was compared with IgM-capture ELISA in 263 serum samples of suspects of Acute Encephalitis Syndrome (AES) and viral fever. Of these 138(52.5%) serum samples showed positive result for JE by PA among which 106 serum samples (77% of PA positive) were also positive by IgM-capture ELISA method. Among 263 serum samples, three of the serum samples were JE negative by PA while positive by IgM-capture ELISA. One hundred twenty two samples were JE negative by both PA and IgM-capture ELISA. PA showed 97% sensitivity and 79% specificity in comparision with IgM-capture ELISA for diagnosis of JE. A positive predictive value of 0.77 and negative predictive value of 0.98 was observed in comparison with IgM-capture ELISA. The result was compatible in comparison with IgM-capture ELISA. To know the cross reactivity, sixteen laboratory confirmed samples of Dengue, Malaria and other infectious diseases were examined for JE by PA. Maximum cross reactivity against dengue was observed with qualitative assay by PA. However with quantitative assay for JE and dengue by PA far greater titre was observed with dengue. Both PA and IgM-capture ELISA showed cross reactivity with Malaria. Since IgM-capture ELISA also showed cross reactivity with Malaria, there is a chance of mixed infection of JE with Malaria. This study showed that particle agglutination assay could be used in rural areas of Nepal for laboratory diagnosis of JE.