Determination of a cut-off value for the serological diagnosis of scrub typhus by detecting anti-Orientia tsutsugamushi immunoglobulin M
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Date
2023-06
Journal Title
Journal ISSN
Volume Title
Publisher
Wolters Kluwer – Medknow
Abstract
Background & objectives: The diagnosis of scrub typhus (ST) is usually done using enzyme-linked immunosorbent assay (ELISA) due to its ease of performance and reading objectivity. The cut-off value for ELISA needs to be calculated for each geographical location as it depends on zonal endemicity of the disease. This study was, therefore, undertaken to calculate the pan-India cut-off for anti-Orientia tsutsugamushi (OT) immunoglobulin M (IgM) by ELISA. Methods: Samples from cases (cases of ST) and controls (voluntary, consenting, healthy adults) were collected by a network of 29 laboratories across India and tested for anti-OT IgM by immunofluorescence assay (IFA), the considered gold standard test. These samples were retested by ELISA for anti-OT IgM and their optical densities (ODs) were used for cut-off estimation by receiver operating characteristic (ROC) curve. Results: Anti-OT IgM ELISA ODs from 273 controls and 136 cases were used for the cut-off estimation. The ODs of the anti-OT IgM ELISA on healthy individuals and those of confirmed ST cases ranged from 0.1 to 0.75 and 0.5 to 4.718, respectively. ROC curve-based cut-off for ELISA was calculated as 0.554 at a sensitivity of 95.2 per cent and specificity of 95.1 per cent. A value of >1 was noted to have a specificity of 100 per cent in diagnosing ST. Interpretation & conclusions: The cut-off calculated for India was similar to the previous cut-off that was used until now.
Description
Keywords
Enzyme-linked immunosorbent assay cut-off, indirect immunofluorescence assay, Orientia tsutsugamushi, immunoglobulin M, scrub typhus
Citation
Jain Amita, Jain Parul, Rebello Sanjay C., Todaria Moulika, Kaur Harmanmeet, Gupta Nivedita, Aggarwal Neeraj, Vijay Neetu, Narayan Jitendra. Determination of a cut-off value for the serological diagnosis of scrub typhus by detecting anti-Orientia tsutsugamushi immunoglobulin M . Indian Journal of Medical Research. 2023 Jun; 157(6): 519-523