Abstract:

Objective: To evaluate the value of the ratio of tuberculosis specific antigen (TBAg) to CD4⁺ T lymphocyte (CD4) count (TBAg/CD4) in the auxiliary diagnosis of AIDS complicated with active pulmonary tuberculosis (PTB). Methods: Basing on the inclusion criteria, a prospective study was conducted in 262 AIDS patients complicated with active PTB from the Fifth People’s Hospital of Suzhou from January 2018 to December 2020.The patients were divided into AIDS+PTB group (n=152) and AIDS group (n=110). The venous blood of patients in the morning of the next day after admission was collected for interferon in vitro release enzyme-linked immunosorbent assay (TB-IGRA), blood routine examination and CD4 detection. The differences of TBAg level and TBAg/CD4 ratio between the two groups were compared. Based on the clinical diagnosis, the efficacy of TB-IGRA in detecting AIDS complicated with PTB was evaluated, and the area under the receiver operating curve (ROC curve) (AUC) was used to determine the best detection index of diagnostic efficacy. Results: Based on the clinical diagnosis, the sensitivity and specificity of TB-IGRA in detecting AIDS complicated with active PTB were 53.95% (82/152) and 75.45% (83/110), respectively. TBAg and TBAg/CD4 levels in the AIDS+PTB group (92.51 (-68.20, 906.10) pg/ml and 1.01 (0.00, 10.12)) were significantly higher than those in the AIDS group (85.20 (-33.80, 801.30) pg/ml and 0.11(0.00, 2.07), respectively), and the antigen concentrations of control culture tube (529.50 (12.50, 1160.50) pg/ml) was significantly lower than that of AIDS group (694.50 (29.90, 990.00) pg/ml)(Z=-3.481, -9.557, 3.289, all P<0.001). ROC curve analysis showed that the AUC values of TBAg and TBAg/CD4 for the diagnosis of AIDS complicated with active PTB were 0.718, 0.637 and 0.842, respectively; when the critical value of TBAg/CD4 was 0.592, the Youden index was the largest, with a sensitivity of 88.10% and a specificity of 77.10%. Conclusion: Compared with AIDS patients, the levels of TBAg and TBAg/CD4 in AIDS patients complicate with PTB were significantly increased, and the diagnostic value of TBAg/CD4 was especially high. Combined with the influence of patients’ immune status, it was considered that TBAg/CD4 had certain auxiliary diagnostic value for AIDS patients with PTB.

Key words: Acquired immunodeficiency syndrome, Tuberculosis,pulmonary, Comorbidity, Antigens,bacterial, CD4 lymphocyte count