Differential positive TSPOT assay responses to ESAT-6 and CFP-10 in health care workers

Saroochi Agarwal, Duc T. Nguyen, Justin D. Lew, Larry D. Teeter, Jose Miguel Yamal, Blanca I. Restrepo, Eric L. Brown, Susan E. Dorman, Edward A. Graviss

Research output: Contribution to journalArticlepeer-review

Abstract

Background: The TSPOT.TB (TSPOT) diagnostic test for latent tuberculosis infection is based on a cell-mediated response to the . Mycobacteria tuberculosis antigens, ESAT-6 and/or CFP-10, producing an "interferon-gamma footprint". We investigated the within-sample and within-subject variability of positive TSPOT assays due to the individual assay antigens' reactivity. Methods: Positive TSPOT assay frequencies due to ESAT-6 or CFP-10 among health care workers (HCWs) at 6-month intervals for 18 months were compared. Differences in result interpretation (positive or negative) for ESAT-6 and CFP10 and potential prognostic factors were investigated. Results: There were 576 positive results in 8805 TSPOT assays representing 2418 participants. A significant difference was detected in positive TSPOT results due to a positive response to either ESAT-6, CFP-10 or both antigens at baseline through 12 M (p < 0.001), but not for the 18 M follow-up. Gender, ethnicity, occupation, previous positive tuberculin skin test (TST) and study site were significantly associated with specific antigen positivity. Conclusions: Among our HCW samples with positive TSPOT assays, CFP-10 induced a larger proportion of positive TSPOT results than ESAT-6. Potential causes for this finding include: BCG vaccinated subpopulations, certain jobs, history of positive TST, U.S. birth, and study site. A high proportion of single-positive specimens may reflect false-positives results.

Original languageEnglish (US)
JournalTuberculosis
DOIs
StateAccepted/In press - 2016

Keywords

  • CFP-10
  • ESAT-6
  • IGRA
  • TSPOT
  • Tuberculosis

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Microbiology (medical)
  • Infectious Diseases

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