title: A rapid, sensitive and reliable diagnostic test for scrub typhus in China.
abstract: OBJECTIVE
  To evaluate the performances for detection of IgM and IgG antibodies to Orientia. tsutsugamushi (Ot) using a gold conjugate-based rapid diagnostic test (RDT).
  
  
  METHODS
  The RDT employing mixture recombinant 56-kDa proteins of O. tsutsugamushi and the mIFA assay was performed on 33 patients from Fujian and Yunnan province respectively and 94 positive sera (36 from Hainan province and 58 from Jiangsu province) from convalescent stages of the patients with scrub typhus respectively and 82 negative sera from healthy farmers from Anhui province and Beijing City respectively in 2009. A comparison of the RDT and mIFA assay was performed by using the χ(2) test and the P level of ≤ 0.05 was considered to be significant.
  
  
  RESULTS
  Among these 94 positive sera from convalescent stages of the illness and 82 sera from control farmers, the specificity of RDT was 100% for both IgM and IgG tests. In 33 cases with scrub typhus, 5 cases were positively detected earlier by RDT than by mIFA for the IgM test, and 2 cases were positive for the IgG test. The sensitivities of RDT were 93.9% and 90.9% for IgM and IgG, respectively. Considering IgM and IgG together, the sensitivity was 100%. The geometric mean titre (GMT) of IFA and the RDT assay in diluted sera from confirmed cases were 1:37 versus 1:113 respectively (P<0.001) for IgM test and 1:99 versus 1:279 respectively (P<0.016) for IgG.
  
  
  CONCLUSIONS
  The RDT was more sensitive than the traditional IFA for the early diagnosis of scrub typhus and was particularly suitable for use in rural areas.
authors: Department of Rickettsiology, National Institute of Communicable Disease Control and Prevention, China CDC, Changping PO Box 5, Beijing 102206, China. zhanglijuan@icdc.cn
authors: Zhang
authors: Z
authors: Lijuan
authors: He
authors: H
authors: Si
authors: Jin
authors: J
authors: Yuming
authors: Li
authors: L
authors: Liang
authors: Li
authors: L
authors: Xuemei
authors: Liu
authors: L
authors: Lianying
authors: Yu
authors: Y
authors: Huilan
authors: Yu
authors: Y
authors: Qiang
authors: Chen
authors: C
authors: Chuangfu
authors: Wang
authors: W
authors: Shiwen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood*; D002648:Child; D002681:China; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D012285:Orientia tsutsugamushi / Q000276:immunology / Q000302:isolation & purification*; D012612:Scrub Typhus / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D007075:Immunoglobulin M