T-Spot.TB Outperforms Tuberculin Skin Test in Predicting Tuberculosis Disease

Rationale: Silicosis is a well-recognized risk factor for tuberculosis (TB).Objectives: To compare T-Spot.TB with tuberculin skin test (TST) in predicting the development of TB.Methods: Male patients with silicosis without clinical suspicion of active TB, past history of TB, and treatment for latent TB infection (LTBI) were offered both T-Spot.TB and TST in the Pneumoconiosis Clinic of Hong Kong from 2004 to 2008, and followed prospectively until September 30, 2009, for development of TB.Measurements and Main Results: Active TB and culture- or histology-confirmed TB developed in 17 (5.5%) and 14 (4.5%) of 308 recruited subjects at an annual rate of 2,247 and 1,851 per 100,000 person-years, respectively. Active TB occurred in 7.4% (15 of 204) and 1.9% (2 of 104) of T-Spot.TB–positive and –negative subjects, respectively, whereas the corresponding figures for TST (cutoff 10 mm) were 6.4% (13 of 203) and 3.9% (4 of 205), respectively. A positive T-Spot.TB test significantly predicted the subsequent developme...