T-SPOT®.TB test and clinical risk scoring for diagnosis of latent tuberculosis infection among Thai healthcare workers.

Abstract

Screening for latent tuberculosis infection (LTBI) is important to identify healthcare workers (HCWs) benefiting from preventive therapy. Interferon-gamma release assays (IGRAs) are sensitive and specific tests for LTBI diagnosis. However, in settings where IGRAs are not available, clinical risk assessment may be used as an alternative to diagnose LTBI. A cross-sectional study was conducted among HCWs of a tertiary-care university hospital in Thailand. All HCWs underwent T-SPOT®.TB test (T-SPOT) and assessment of LTBI clinical risks. Clinical risks associated with T-SPOT positivity were determined by multivariable logistic regression analysis and were given scores accordingly. The performance of the clinical risk scoring was evaluated in comparison to T-SPOT. Among 140 enrolled HCWs, 125 (89%) were females, the median age was 27 years and 23 (16%) had T-SPOT positivity. Independent factors associated with T-SPOT positivity were age ≥30 years (adjusted odds ratio [aOR] 3.95; P=0.002), working duration ≥60 months (aOR 3.75, P=0.004) and frequency of TB contact ≥6 times (aOR 8.83, P=0.005). The study's clinical risk scoring had the area under the curve by receiver operating curve analysis of 0.76 (P<0.001) using T-SPOT positivity as a reference standard. The score of ≥3 had the best performance in diagnosing LTBI with sensitivity, specificity, positive predictive value and negative predictive value of 70%, 71%, 32% and 92%, respectively. In this setting where LTBI was prevalent among HCWs but IGRAs are not widely available, the clinical risk scoring may be used as an alternative to diagnose LTBI in HCWs.