Factors associated with false-negative for T-SPOT.TB in patients with TB disease

T-SPOT.TB is an adjunctive diagnostic tool that is used for detecting TB disease. However, in some patients with TB disease, a false-negative result can occur. This study aims to determine the factors that are associated with false-negative T-SPOT.TB results in TB disease. We retrospectively enrolled 210 patients who were diagnosed with TB disease and underwent T-SPOT.TB testing between July 2014 and July 2020 at Ramathibodi Hospital Bangkok, Thailand. Clinical characteristics, laboratory findings and radiographic findings were compared between the false-negative and true-positive T-SPOT.TB groups. Among 210 patients with TB disease, 144 patients had pulmonary TB, 44 patients had extrapulmonary TB and 22 patients had concomitant pulmonary and extrapulmonary TB. There were 100 male and 110 female patients, with a mean age of 54.1 ± 17.5 years. Ninety patients (42.9%) had false-negative T-SPOT.TB results. Multivariate analysis showed that increased age was significantly associated with false-negative T-SPOT.TB (OR 1.025, 95% CI 1.008-1.043, P = 0.006). Those aged ≥55 years had 1.8 times higher false-negative T-SPOT.TB rate than the younger group (age ≥55 years: 64.4% vs. age <55 years: 35.6%; P = 0.001). Advanced age, particularly age ≥55 years, was a significant factor that related with false-negative T-SPOT.TB results in TB disease.