Prospective evaluation of an ELISA and Western Blot for the diagnosis of endemic strongyloides stercoralis infection - abstract

ABSTRACT

Strongyloides stercoralis is the most serious intestinal nematode infecting humans in the Caribbean. The parasite is, however, difficult to diagnose using standard laboratory techniques, especially in sub-clinical cases. An ELISA, using PBS extracts of filariform larvae as antigen, and a Western Blot method were evaluated in the Jamaican community. Sensitivity and specificity of the ELISA were 73 per cent and 93 per cent (n=135) respectively. Pre-incubation of sera with Onchocerca gutterosa (Filariata) antigen increased sensitivity and specificity of the ELISA to 82 per cent and 97 per cent, respectively. Similarly, The Western Blot which was based on IgG recognition of proteins of 41kD and one of 31kD or 28kD detected 82 per cent of infected individuals and 97 per cent of true negatives. There was no notable cross-reactivity by either ELISA or Western Blot with Ascaris, Trichuris or hookworm, also common to the Region. ELISA proved to be a sensitive and specific test for diagnosing S. stercoralis infection in Jamaica. Western Blotting had no significant merits over those of ELISA although it confirmed the presence of 3 immunodominant bands which may play a role in future immunodiagnosis. Furthermore, it adds to the battery of sensitive serological tests available to clinicians who have to decide on the infection status of potential S. stercoralis patients who are about to receive immuno-suppressive therapy (AU)