High prevalence and risk factors of positive sputum smear in newly diagnosed pulmonary tuberculosis patients in Vietnam.

Objectives: To assess the prevalence and identify risk factors associated with smear-positive tuberculosis (acid-fast bacilli [AFB]-positive) in newly diagnosed patients in Vietnam. Methods: A retrospective study was conducted on patients newly diagnosed with pulmonary tuberculosis (PTB) from August 2023 to August 2024. Patients were classified as smear-positive if at least one respiratory sample tested positive with AFB before starting anti-tuberculosis treatment. Smear-negative individuals had to submit a minimum of two sputum samples, all of which had to test negative before treatment initiation. Results: 379 PTB patients were included with 48.3% being AFB-positive. The proportion of hemoptysis was significantly higher in AFB-positive than in AFB-negative patients (9.8% versus 4.1%, p=0.04). AFB-negative patients had a significantly higher rate of fatigue and crackles compared to AFB-positive patients with 85.7% versus 77.0%, p=0.03 and 36.2% versus 25.7%, p=0.03, respectively. Cavitary lung lesions were significantly more common in AFB-positive patients (48.6% versus 29.1%, p<0.0001). In multivariate analysis, patients with diabetes mellitus and those with long-term corticosteroid use were respectively three times and six times more likely to be AFB-positive (OR=2.71, p=0.002 and OR=6.15, p=0.009) more likely to. Cavitation in chest-x-ray was also associated with 2.5 times of risk for smear-positive (OR=2.53, p <0.0001). All of three HIV-coinfected patients were AFB-negative. Conclusion: Our findings emphasize the importance of screening and early diagnosis of PTB in individuals with diabetes mellitus and in those on long-term corticosteroid therapy. Strengthening TB control efforts, particularly among high-risk populations, is crucial to reducing the burden of smear-positive TB and preventing further transmission.