Comparison of Commercial Enzyme-Linked Immunosorbent Assay and Immunofluorescence Assay for Diagnosis of Acute Rickettsia typhi Infections

Abstract

Murine typhus is a tropical disease caused <i>by Rickettsia typhi</i> and is endemic in resource-limited settings such as Southeast Asian countries. Early diagnosis of <i>R. typhi</i> infection facilitates appropriate management and reduces the risk of severe disease. However, molecular detection of <i>R. typhi</i> in blood is insensitive due to low rickettsemia. Furthermore, the gold standard of sero-diagnosis by immunofluorescence assay (IFA) is cumbersome, subjective, impractical, and unavailable in many endemic areas. In an attempt to identify a practical diagnostic approach that can be applied in Indonesia, we evaluated the performance of commercial <i>R. typhi</i> IgM and IgG enzyme-linked immunosorbent assay (ELISA) and IFA using paired plasma from previously studied <i>R. typhi</i> PCR-positive cases and controls with other known infections. Sensitivity and specificity of combined ELISA IgM and IgG anti-<i>R. typhi</i> using paired specimens were excellent (95.0% and 98.3%, respectively), comparable to combined IFA IgM and IgG (97.5% and 100%, respectively); sensitivity of ELISA IgM from acute specimens only was poor (45.0%), but specificity was excellent (98.3%). IFA IgM was more sensitive (77.5%), but less specific (89.7%) for single specimens.

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