J Korean Med Sci.  2016 Aug;31(8):1190-1196. 10.3346/jkms.2016.31.8.1190.

Clinical Evaluation of Rapid Diagnostic Test Kit for Scrub Typhus with Improved Performance

• Kim YJ
• Park S
• Premaratna R
• Selvaraj S
• Park SJ
• Kim S
• Kim D
• Kim MS
• Shin DH
• Choi KC
• Kwon SH
• Seo W
• Lee NT
• Kim SH
• Kang HK
• Kim YW

• KMID: 2373744
• DOI: http://doi.org/10.3346/jkms.2016.31.8.1190

Abstract

Diagnosis of scrub typhus is challenging due to its more than twenty serotypes and the similar clinical symptoms with other acute febrile illnesses including leptospirosis, murine typhus and hemorrhagic fever with renal syndrome. Accuracy and rapidity of a diagnostic test to Orientia tsutsugamushi is an important step to diagnose this disease. To discriminate scrub typhus from other diseases, the improved ImmuneMed Scrub Typhus Rapid Diagnostic Test (RDT) was evaluated in Korea and Sri Lanka. The sensitivity at the base of each IgM and IgG indirect immunofluorescent assay (IFA) in Korean patients was 98.6% and 97.1%, and the specificity was 98.2% and 97.7% respectively. The sensitivity and specificity for retrospective diagnosis at the base of IFA in Sri Lanka was 92.1% and 96.1%. ImmuneMed RDT was not reactive to any serum from seventeen diseases including hemorrhagic fever with renal syndrome (n = 48), leptospirosis (n = 23), and murine typhus (n = 48). ImmuneMed RDT shows superior sensitivity (98.6% and 97.1%) compared with SD Bioline RDT (84.4% at IgM and 83.3% at IgG) in Korea. The retrospective diagnosis of ImmuneMed RDT exhibits 94.0% identity with enzyme-linked Immunosorbent assay (ELISA) using South India patient serum samples. These results suggest that this RDT can replace other diagnostic tests and is applicable for global diagnosis of scrub typhus. This rapid and accurate diagnosis will be beneficial for diagnosing and managing scrub typhus.

Keyword

Rapid Diagnostic Test; Scrub Typhus; Orientia tsutsugamushi

MeSH Terms

Antibodies, Bacterial/blood
Enzyme-Linked Immunosorbent Assay
Fluorescent Antibody Technique, Indirect
Humans
Immunoglobulin G/blood
Immunoglobulin M/blood
Orientia tsutsugamushi/immunology
Reagent Kits, Diagnostic
Retrospective Studies
Scrub Typhus/*diagnosis/microbiology
Sensitivity and Specificity
Antibodies, Bacterial
Immunoglobulin G
Immunoglobulin M
Reagent Kits, Diagnostic

Figure

• 

  Fig. 1 Representative pictures for RDT indicating negative and positive results. Red colorization of the test line (T) indicates the presence of human antibody against O. tsutsugamushi and the red control line (C) represents the valid test result. Demonstration is negative (kit 1), both positive in IgM and IgG (kit 2), IgM positive (kit 3), and IgG positive (kit 4) in RDT results.

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