Determination of Optimal Diagnostic Cut-Offs for the Naval Medical Research Centre Scrub Typhus IgM ELISA in Chiang Rai, Thailand.

Determination of Optimal Diagnostic Cut-Offs for the Naval Medical Research Centre Scrub Typhus IgM ELISA in Chiang Rai, Thailand. Am J Trop Med Hyg. 2019 Mar 11;: Authors: Phanichkrivalkosil M, Tanganuchitcharnchai A, Jintaworn S, Kantipong P, Laongnualpanich A, Chierakul W, Paris DH, Richards AL, Wangrangsimakul T, Day NPJ, Blacksell SD Abstract In this diagnostic accuracy study, we evaluated data from 135 febrile patients from Chiang Rai, to determine the optimal optical density (OD) cutoffs for an in-house scrub typhus IgM ELISA. Receiver operating characteristic curves were generated using a panel of reference assays, including an IgM immunofluorescence assay (IFA), PCR, in vitro isolation, presence of an eschar, or a combination of these. Altogether, 33 patients (24.4%) were diagnosed as having scrub typhus. Correlation between positivity by IFA and increasing OD values peaked at a cutoff of 2.0, whereas there was little association between positivity by culture or eschar with increasing ELISA cutoffs-cutoffs of 3.0 and 4.0 were demonstrated to be optimal for the total absorbance of the OD at dilutions 1:100, 1:400, 1:1,600, and 1:6,400, for admission and convalescent samples, respectively. The optimal cutoff at a 1:100 dilution was found to be between 1.85 and 2.22 for admission samples and convalescent-phase samples, respectively. Sensitivities for the cutoffs varied from 57.1% to 90.0% depending on the reference test and sam...
Source: Am J Trop Med Hyg - Category: Infectious Diseases Authors: Tags: Am J Trop Med Hyg Source Type: research