| Abstract: | Using archived samples, we assessed the diagnostic capacity of a rapid immunochromatographic test (ICT) for the detection of Orientia tsutsugamushi IgM and total antibodies to aid with the diagnosis of acute scrub typhus infection in febrile patients in Laos. The sensitivity and the specificity of the ICT for the detection of IgM were 96.8% (121/125 samples; 95% confidence interval CI], 92.1 to 99.1%) and 93.3% (98/105 samples; 95% CI, 86.7 to 97.3%), respectively. For the detection of total antibodies, the sensitivity was 97.6% (122/125 samples; 95% CI, 93.1 to 99.5%), but the specificity was much lower, at 71.4% (75/105 samples; 95% CI, 61.8 to 79.8%).Scrub typhus, caused by Orientia tsutsugamushi, is an important acute febrile illness in the Asia-Pacific region. As very few health facilities have accessible accurate diagnostic tests, the diagnosis of scrub fever must be based on clinical features. However, this is difficult because the clinical symptoms and signs are similar to those of many other febrile diseases, such as murine typhus, leptospirosis, and dengue virus infection. The diagnosis of scrub typhus infection has relied on the detection of O. tsutsugamushi antibodies during the acute phase of the disease, and the “gold standard” assay is the indirect immunofluorescence antibody assay (IFA) (9). The development of rapid, diagnostic tests by the use of immunochromatographic test (ICT) technologies has provided a mechanism for point-of-care serological testing. The objective of the study described here was to assess the diagnostic capacities of two commercial rapid ICTs for the detection of O. tsutsugamushi IgM and whole antibodies to aid with the diagnosis of acute scrub typhus infection by the use of stored, characterized sera collected from febrile patients in the tropical environment of the Lao People''s Democratic Republic (Laos) and Thailand where scrub typhus is endemic. |
