Association of clinical laboratory parameters with latent tuberculosis infection among healthcare workers of primary health centers―A cross-sectional observational study

Healthcare workers (HCWs) are at high risk of tuberculosis (TB) infection due to their continued occupational exposure to patients with active TB disease. The prevalence of latent TB infections (LTBI) among the HCWs of primary healthcare centers (PHCs) has seldom been investigated. PHCs provide effective and preventive medical care largely for the rural population. Comparatively, the HCWs of PHCs are likely to have an increased risk of occupational exposure and reactivation of LTBI. A cross-sectional study (March-April 2024) was carried out to assess the prevalence of LTBI among the HCWs of 64 PHCs across Thiruvallur district, India. Blood samples (n = 392) were analyzed using a commercial QuantiFERON-TB Gold Plus assay. A comprehensive hematological, biochemical, and immunological workup was performed, including cell count, blood glucose determination, liver/renal function tests, and serum ferritin concentration estimation, which were subsequently correlated with LTBI status using multivariate logistic regression analysis. The study revealed an LTBI prevalence of 25.3% (n = 99) among HCWs of PHCs. The red cell distribution width (RDW) was significantly associated (p = 0.002) with LTBI positivity among the different parameters analyzed. Factors such as individuals' age (p = 0.029), underlying comorbid conditions (30.3%; p = 0.035), and longer employment duration (28%; p = 0.034) were significantly associated with IGRA positivity. Further, IGRA positivity was significantly associated with decreased RDW standard deviation (RDW-SD). This phenomenon was observed especially among females, the obese, and participants with the 'O' blood group. Although the exact prevalence of LTBI in the general population is not known, it is estimated to range from 20-48%. The study reported the prevalence of LTBI among HCWs of PHCs (25.3%) and factors associated with IGRA positivity including age, underlying comorbid conditions, and years of employment. Our findings will aid in developing and establishing an appropriate framework for TB screening and clinical testing guidance for HCWs.