Objective: To evaluate the cost-effectiveness of a dual strategy of tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT-G) for screening of latent tuberculosis infection (LTBI) in healthcare workers (HCWs) and, as a secondary objective, to study relationships between TST results, QFT-G results, and sociodemographic factors.
Design: Cross-sectional prospective study.
Setting: University hospital in Madrid.
Participants: A total of 103 HCWs.
Methods: QFT-G was requested for all positive TST results; QFT-G results were compared with TST results, and their relationships with sociodemographic factors were analyzed. A cost-effectiveness analysis was conducted for the dual strategy (TST/QFT-G) and for TST or QFT alone, taking into account the indication of and compliance with isoniazid, the risk of hepatotoxicity, and postexposure tuberculosis.
Results: Of all HCWs studied, 42.3% showed a positive result by QFT-G, and 49.5% had received bacille Calmette-Guérin (BCG) vaccination; no significant association was detected between BCG and QFT-G results. Increased TST was linked to higher positive QFT-G values (TST of 5-9.9 mm, 27.6%; TST of 15 mm or more, 56.5%; P=.03). The probability of positive QFT-G results was 1.04 times higher for each year of age (odds ratio, 1.04 [95% confidence interval, 1.01-1.09]; P=.0257). The incremental cost per active TB case prevented was lower for TST/QFT-G than for the other strategies studied (€14,211 per 1,000 HCWs). The number of people treated for LTBI per case of active TB prevented (number needed to treat) for TST/QFT-G was lower than for TST alone (17.2 vs 95.3 and 88.7 with the 5- and 10-mm cutoff value, respectively) or QFT-G alone (69.6).
Conclusions: Dual strategy with TST/QFT-G is more cost-effective than TST or QFT-G alone for the diagnosis of LTBI in HCWs.