Comparative Accuracy of the InBios Scrub Typhus Detect IgM Rapid Test for the Detection of IgM Antibodies by Using Conventional Serology

Abstract

This study investigated the comparative accuracy of a recombinant 56-kDa type-specific antigen-based rapid diagnostic test (RDT) for scrub typhus for the detection of IgM antibodies by using conventional serology in well-characterized serum samples from undifferentiated febrile illness patients. The RDT showed high specificity and promising comparative accuracy, with 82% sensitivity and 98% specificity for samples defined positive at an IgM indirect immunofluorescence assay positivity cutoff titer of ≥1:1,600 versus 92% and 95% at ≥1:6,400, respectively.

Prevalence and risk factors for scrub typhus in South India

“…Notably, our study used more conservative ELISA cut‐off values than the prior study in South India. Additionally, the ELISA assay used in this study, although highly specific (98%), does have a lower sensitivity (82–84%) . Therefore, it is possible that our study understates the current prevalence.…”

“…Ideally, a larger representative survey of a broader area of South India that worked to motivate young men to participate would be performed to confirm our findings. Finally, the assay used to assess prior exposure may be insensitive, particularly as prior studies looking at the sensitivity were carried out in symptomatic individuals and still only found an 82–84% sensitivity . We used more stringent cut‐offs, which, although increasing the specificity likely decreased the sensitivity further.…”

Assessment of two immunoassays for detection of IgM antibodies to scrub typhus using a serum panel

“…17,18,19 to determine optimal RDT performance with antibody titre in IFA as comparator. 25 The results…”

Scrub Typhus Meningitis versus Acute Bacterial Meningitis—A Clinical-Laboratory Differential Diagnosis

“…However, we speculate that the lower-CSF glucose concentration and high-protein concentrations typically seen in tuberculous meningitis, together with the frequency of focal signs in tuberculous meningitis, would help in differentiating the two conditions; moreover, elevated transaminase concentrations, which would be unusual in tuberculous meningitis, would help point to a diagnosis of STM. Second, although indirect fluorescent antibody (IFA) test is the gold standard for serodiagnosis of scrub typhus, 13,[29][30][31] this test is not yet widely available in India.…”