Background: Interferon gamma release assays (IGRA) is highly specific for Mycobacterium tuberculosis and is the preferred test in BCG-vaccinated individuals. The few studies that have screened health care workers (HCWs) in Saudi Arabia for latent tuberculosis infection (LTBI) using IGRA have varied in agreement with the traditional tuberculin skin test (TST).
Objective: Assess the prevalence of LTBI among HCWs working in the Hajj pilgrimage using IGRA and TST and measuring their agreement.
Design: Cross-sectional prospective.
Setting: Multiple non-tertiary care hospitals.
Patients and methods: HCWs who worked during the Hajj pilgrimage in Saudi Arabia in December 2015. Data was collected by standarized questionnaire. Samples were drawn and analyzed by standard methods.
Main outcome measures: The prevalence of LTBI among HCW and the agreement by kappa statistic between QFT-GIT and TST.
Sample size: 520 subjects.
Results: Nurses accounted for 30.7% of the sample and physicians, 19.2%. The majority were BCG vaccinated (98.5%). There were a total of 56 positive by QFT-GIT and the LTBI rate was 10.8%. In 50 QFT positive/476 TST negative the LTBI rate was 10.5% in discordant tests, and in 6 QFT positive/44 TST positive it was 13.6% in concordant tests. The overall agreement between both tests was poor-83% and kappa was 0.02. LTBI prevalence was associated with longer employment (13.1 [9.2] years). The QFT-GIT positive test was significantly higher in physicians (P=.02) and in HCWs working in chest hospitals 16/76 (21.05%) (P=.001).
Conclusion: Agreement between the tests was poor. QFT-GIT detected LTBI when TST was negative in HCWs who had a history of close contact with TB patients.
Limitations: A second step TST was not feasible within 2-3 weeks.
Conflict of interest: None.