{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T13:58:35Z","timestamp":1782827915117,"version":"3.54.5"},"reference-count":40,"publisher":"American Society of Tropical Medicine and Hygiene","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2019,5,1]]},"abstract":"<jats:p>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<jats:strike>\u2014<\/jats:strike>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 sample timing, whereas specificities ranged from 85.2% to 99.0%. We therefore recommend a cutoff of around 2.0, depending on the sensitivity and specificity desired in clinical or epidemiological settings. The results demonstrate the ELISA to be a valuable diagnostic tool, suitable for use in resource-limited endemic regions, especially when used in combination with other diagnostic modalities such as the presence of an eschar.<\/jats:p>","DOI":"10.4269\/ajtmh.18-0675","type":"journal-article","created":{"date-parts":[[2019,3,12]],"date-time":"2019-03-12T07:01:23Z","timestamp":1552374083000},"page":"1134-1140","source":"Crossref","is-referenced-by-count":18,"title":["Determination of Optimal Diagnostic Cut-Offs for the Naval Medical Research Center Scrub Typhus IgM ELISA in Chiang Rai, Thailand"],"prefix":"10.4269","volume":"100","author":[{"given":"Meghna","family":"Phanichkrivalkosil","sequence":"first","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ampai","family":"Tanganuchitcharnchai","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Suthatip","family":"Jintaworn","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pacharee","family":"Kantipong","sequence":"additional","affiliation":[{"name":"Chiangrai Prachanukroh Hospital, Chiang Rai, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Achara","family":"Laongnualpanich","sequence":"additional","affiliation":[{"name":"Chiangrai Prachanukroh Hospital, Chiang Rai, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wirongrong","family":"Chierakul","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel H.","family":"Paris","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"},{"name":"Department of Medicine, Swiss Tropical and Public Health Institute, Basel, Switzerland;"},{"name":"Faculty of Medicine, University of Basel, Basel, Switzerland;"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allen L.","family":"Richards","sequence":"additional","affiliation":[{"name":"Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, Maryland;"},{"name":"Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, Maryland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tri","family":"Wangrangsimakul","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicholas P. J.","family":"Day","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stuart D.","family":"Blacksell","sequence":"additional","affiliation":[{"name":"Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand;"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom;"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"2795","reference":[{"key":"b1","series-title":"J Clin Microbiol","first-page":"1472","article-title":"Optimal cutoff and accuracy of an IgM enzyme-linked 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