title: Accuracy of rapid IgM-based immunochromatographic and immunoblot assays for diagnosis of acute scrub typhus and murine typhus infections in Laos.
abstract: We studied the diagnostic accuracy of a rapid immunochromatographic test (ICT) for detection of IgM against scrub typhus (ST ICT) and an immunoblot test for the detection of IgM against murine typhus (MT IBT) by using admission serum samples from 1,030 febrile patients in Laos. Sensitivity and specificity for the ST ICT determined by using the diagnostic criteria of a four-fold increase in IgM against Orientia tsutsugamushi between paired samples were 23.8% (95% confidence interval [CI] = 15.9-33.3%) and 86.2% (95% CI = 84.1-88.6%), respectively. Sensitivity and specificity for the ST ICT determined by using an admission IgM titer > or = 1:400 were 39.1% (95% CI = 34.1-44.2%) and 99.5% (95% CI = 98.7-99.9%), respectively. Sensitivity and specificity for the MT IBT determined by using the criteria of a four-fold increase in IgM against Rickettsia typhi between paired serum samples were 61.2% (95% CI = 53.7-68.3%) and 86.5% (95% CI = 84.1-88.8%), respectively. Sensitivity and specificity for the MT IBT determined by using an admission IgM titer > or = 1:400 were 54.6% (95% CI = 49.1-60.0%) and 94.1% (95% CI = 92.0-95.7%), respectively. Both assays had relatively good specificity but low sensitivity and thus have limited utility for admission diagnosis.
authors.affiliation: Wellcome Trust-Mahosot Hospital-Oxford Tropical Medicine Research Collaboration, Microbiology Laboratory, Mahosot Hospital, Vientiane, Laos. stuart@tropmedres.ac
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Blacksell
authors.forename: Kemajittra
authors.initials: K
authors.lastname: Jenjaroen
authors.forename: Rattanaphone
authors.initials: R
authors.lastname: Phetsouvanh
authors.forename: Ampai
authors.initials: A
authors.lastname: Tanganuchitcharnchai
authors.forename: Phonlavanh
authors.initials: P
authors.lastname: Phouminh
authors.forename: Simalee
authors.initials: S
authors.lastname: Phongmany
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.forename: Paul N
authors.initials: PN
authors.lastname: Newton
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D002648:Child; D002845:Chromatography; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D015151:Immunoblotting / Q000592:standards; D007075:Immunoglobulin M / Q000097:blood*; D012285:Orientia tsutsugamushi / Q000276:immunology; D012286:Rickettsia typhi / Q000276:immunology; D012612:Scrub Typhus / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D014437:Typhus, Endemic Flea-Borne / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D007075:Immunoglobulin M