Diagnosis of Latent Tuberculosis Infection Using Interferon-gamma Release Assay and Interleukin-2 among Healthcare Workers

Background: Latent tuberculosis infection (LTBI) that could be converted to active TB constitutes a major public health problem. LTBI diagnosis is based on TST and/or IGRA. Serum IL-2 may help LTBI diagnosis. Objectives: Current study aimed to estimate the prevalence of LTBI among healthcare workers (HCWs), and to test the agreement between IGRA and IL-2 assay for detection of LTBI. Methods: The study was carried in chest hospitals in Egypt, 89 HCWs were included. Detailed medical history was obtained, and a blood sample was collected to measure IFN-γ and IL-2. Results: High prevalence of LTBI was detected among HCWs (41.57%). This was significantly associated with older age and longer duration of work. Doctors were less exposed to the risk of LTBI. Assessing IL-2 results using ROC curve: AUC was 0.984, optimal cut-off value =13.81 pg/ml, with a sensitivity of 94.59% and 100% specificity. IL-2 responses were higher among participants with LTBI compared to No TB. Conclusions: A high prevalence of LTBI was observed among HCWs. Older age and longer duration of work were associated with higher risk. IL-2/IFN-γ ratios may improve the ability of IGRA to identify individuals with LTBI and those at increased risk of conversion to active disease.