Objective  To investigate the influencing factors of false negative of T-cell spot test for tuberculosis infection (T-SPOT.TB).

Methods  A total of 473 patients diagnosed with active pulmonary tuberculosis (APTB) in the Fifth Affiliated Hospital Affiliated to Sun Yat-sen University from October 2019 to April 2021 were selected, and divided into negative group (78 cases) and positive group (395 cases) according to T-SPOT.TB results. The demographic characteristics, clinical characteristics and laboratory results of the two groups were compared, and the influencing factors of false negative T-SPOT.TB were screened; the multivariate Logistic regression analysis was used to screen the independent influencing factors of false negative T-SPOT.TB.

Results  The results of T-SPOT.TB were not affected by gender, negative smear, initial treatment or retreatment, imaging findings with or without cavities, diabetes mellitus and tuberculous pleurisy. Older age, increased urea, decreased total protein and albumin were the influencing factors of false negative T-SPOT.TB. The false negative rates of T-SPOT.TB in APTB patients ≤25 years old, 26 to 45 years old, 46 to 65 years old and >65 years old were 5.88%, 11.51%, 19.19% and 26.60%, respectively, showing an increasing trend (P < 0.001). Spearman rank correlation analysis showed that the definition values of each age group were negatively correlated with T-SPOT.TB results (r=-0.183, P < 0.001). Multivariate Logistic regression analysis showed that age >65 years was an independent influencing factor for false negative T-SPOT.TB. Compared with age ≤25 years old, the OR value of false negative T-SPOT.TB.in age>65 years old was 3.896 (95%CI, 1.228~12.361), P=0.021.

Conclusion  Age>65 years of APTB patients is an independent risk factor for false negative T-SPOT.TB.