Influencing factors for pcr-fluorescent probe detection results in patients with lymph node tuberculosis: A retrospective observational study

Lymph node tuberculosis (LNTB) is the most common form of extrapulmonary tuberculosis, and its diagnosis and drug resistance screening remain challenging due to low positivity rates of conventional microbiological tests. The polymerase chain reaction (PCR)-fluorescent probe method has been widely used for rapid detection of Mycobacterium tuberculosis, but factors influencing its detection positivity in LNTB remain insufficiently explored. This study aimed to investigate the influencing factors of PCR-fluorescent probe detection positivity and preliminarily explore the dose‑response relationships between age, T lymphocyte subsets, and PCR-fluorescent probe results in patients with LNTB. The clinical data of 411 patients with LNTB admitted to Xi'an Chest Hospital from November 30, 2018 to June 17, 2024 were retrospectively analyzed. The influencing factors were screened by univariate + multivariate logistic regression analysis. Furthermore, the dose-response relationship between PCR-fluorescent probe detection results and age and T lymphocyte subsets was analyzed using a restricted cubic spline model. The results of multivariate logistic regression analysis indicated that obtaining samples through surgery (odds ratio [OR] = 3.01, 95% confidence interval [CI] 1.45-6.26), the number of samples (OR = 3.03, 95% CI 1.69-5.44), the second quartile of age (OR = 2.95, 95% CI: 1.41-6.19), and the third quartile of cluster of differentiation (CD)4+ CD8+ T helper/T suppressor cells (OR = 2.75, 95% CI: 1.29-5.85) increased the risk of positive PCR- fluorescent probe results. In contrast, the third quartile of total T lymphocyte CD3+ (OR = 0.42, 95% CI: 0.21-0.87) decreased the risk of positive PCR-fluorescent probe results. Additionally, the second, third, and fourth quartile indices of T helper lymphocytes CD3+ CD4+ all reduced the risk of positive PCR-fluorescent probe results (Ptrend < .05). There was a nonlinear dose-response relationship between age (Poverall trend < .001, Pnonlinear < .001), total T lymphocyte CD3+ (Poverall trend = .017, Pnonlinear = .014), and the positive risk of PCR-fluorescent probe detection results. Conversely, a linear dose-response relationship was observed between CD3+ CD4+ (Poverall trend = .026, Pnonlinear = .116) and the positive risk of PCR-fluorescent probe detection results. The positive outcomes of PCR-fluorescence probe detection are facilitated by obtaining samples through surgery and an increased number of samples. Furthermore, both linear and nonlinear dose-response relationships were observed between age, T lymphocyte subsets, and the results of PCR-fluorescence probe detection.