Optimal Cutoff Titers for Indirect Immunofluorescence Assay for Diagnosis of Scrub Typhus

We determined the optimal cutoff titers in admission and convalescent-phase samples for scrub typhus indirect immunofluorescence assay using Bayesian latent class models. Cutoff titers of >= 1:3,200 in an admission sample or of a >= 4-fold rise to >= 1: 3,200 in a convalescent-phase sample provided the highest accuracy (sensitivity, 81.6%; specificity, 100%).