Laboratory detection of strongyloidiasis: IgG‐, IgG4‐ and IgE‐ELISAs and cross‐reactivity with lymphatic filariasis

Summary Enzyme‐linked immunosorbent assays (ELISAs) were developed for the detection of I g G , I g G 4 and I g E antibodies against S trongyloides stercoralis . A commercial ELISA ( IVD Research, USA) was also used, and the sensitivities and specificities of the four assays were determined. Serum samples from 26 patients with S . stercoralis infection and 55 patients with other infections or no infection were analysed. Sensitivities of the I g G 4 , I g G , I g E and I g G ( IVD ) assays were 76·9%, 84·6%, 7·7% and 84·6%, respectively, while the specificities were 92·7%, 81·8%, 100% and 83·6%, respectively. If filariasis samples were excluded, the specificities of the I g G 4 ‐ ELISA and both I g G ‐ ELISA s increased to 100% and 98%, respectively. A significant positive correlation was observed between I g G ‐ and I g G 4 ‐ ELISA s ( r = 0·4828; P = 0·0125). I g G ‐ and I g G ‐ ( IVD ) ELISA s ( r = 0·309) were positively correlated, but was not significant ( P = 0·124). Meanwhile there was no correlation between I g G 4 ‐ and I g G ‐ ( IVD ) ELISA s ( r = 0·0042; P = 0·8294). Sera from brugian filariasis patients showed weak, positive correlation between the titres of antifilarial IgG 4 and the optical densities of anti‐ Strongyloides I g G 4 ‐ ELISA ( r = 0·4544, P = 0·0294). In conclusion, the detection of both anti‐ Strongyloides I g G 4 and I g G antibodies could improve the serodiagnosis of human strongyloidiasis. Furthermore, patients from lymphatic filariasis endemic areas who are serologically diagnosed with strongyloidiasis should also be tested for filariasis.