Kinetics of IgM and IgG antibodies after scrub typhus infection and the clinical implications. (June 2018)

• Record Type: Journal Article
• Authors: Varghese, George M.; Rajagopal, Veera Manikandan; Trowbridge, Paul; Purushothaman, Divya; Martin, Sherry Joseph
• Is Part Of: International journal of infectious diseases. Volume 71(2018)
• Page Start: 53
• Page End: 55
• Publication Date: 2018-06
• Subjects: Scrub typhus -- IgM -- IgG -- Kinetics -- Orientia tsutsugamushi -- Rickettsia; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2018.03.018
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: The kinetics of IgM and IgG post scrub typhus infection remain elusive. Scrub typhus patients were followed up to study antibody kinetics. IgM remained above the threshold for 12 months. IgG reached a peak at 10 months and remained above the threshold for 36 months. Paired IgM samples are required for accurate diagnosis. Abstract: Objectives: The serological detection of IgM antibodies is the most widely used test to diagnose scrub typhus infection. However, the kinetics of IgM and IgG antibodies post-infection remain elusive, which could contribute to false positivity. The objective of this study was to document the nature of the evolution of these antibody titres after infection. Methods: Adult patients previously confirmed to have scrub typhus by IgM ELISA, positive PCR, or both, were included in this cross-sectional study. The levels of IgM and IgG antibodies in serum samples were tested using an ELISA and the distribution curve was plotted. Results: Two hundred and three patients were included in this study. Post-infection serum sampling was done between 1 month and 46 months after documented infection. IgM levels declined gradually but remained elevated above the diagnostic cut-off for up to 12 months post-infection. However, IgG levels continued to rise reaching a peak at 10 months, followed by a gradual decline over several months. In the majority of cases, the IgG levels remained above the cut-off threshold for more than 36 months. Conclusions: Clinicians need to be cautious in using a single serum sample for the detection of IgM to diagnose scrub typhus, as it remains elevated for up to 12 months after the infection, whereas the serum IgG level could be used as an indicator of past infection.