Prospective study with rapid and low cost serodiagnostic assay for rickettsial infections in children of Vijayapura district, Northern Karnataka, India

Abstract

Background: Rickettsial infections do exist in study area posing diagnostic difficulties. The study is aimed to compare performance of serological assays for rapid and low-cost diagnosis for rickettsial infections in northern Karnataka, India.Methods: Prospective study was done on 40 children upto 12 years old, hospitalized during 1-year period with fever and presence of one or more of the clinical features of rickettsial infections. Clinical and biochemical findings and serological assays such as indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay-IgM (ELISA-IgM) and Weil-Felix were used to diagnose the disease. Statistical analysis was used to compare the results. Performance characteristics such as sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated using MedCalc for Windows.Results: All 40 patients met the inclusion criteria (23 males and 17 females). Mortality was 2%. Predominant age group was 1-3 years (57.50%). Fever, rashes and hepatosplenomegaly was in all 40 patients (100%); whereas other clinical features showed mixed results. Biochemical findings: anemia in 90%, thrombocytopenia in 45% and elevated transaminases 57.50% and 55%. The ELI-SA-IgM assay showed a sensitivity of 95.00%, a specificity of 95.24% and 95.12% accuracy. The Weil-Felix assay showed a sensitivity of 77.50%, a specificity of 81.63% and 79.78% accu-racy. ELISA-IgM test showed only 5% (p=0.5555) and Weil-Felix test showed 12.50% (p=0.3816) non-significant difference when both compared with IFA test. Whereas ELISA-IgM showed 17.50% more significant (p=0.0239) when compared with Weil-Felix.Conclusions: ELISA-IgM may serve as rapid and low cost serodiagnostic assay over IFA for rickettsial infections.