TB sputum smear positivity rose during Taiwan’s COVID-19 transition, study finds

Sputum acid-fast bacilli smear positivity was higher among adults newly diagnosed with pulmonary tuberculosis during Taiwan’s COVID-19 transition period than before the pandemic, according to a retrospective cross-sectional study conducted at a medical center in southern Taiwan. The increase was not accompanied by a corresponding rise in radiographically documented cavitary pulmonary disease.

Researchers analyzed 789 consecutive adults diagnosed with pulmonary tuberculosis from 2017 through 2024 and divided them into three time periods: the pre-pandemic period of 2017–2019, the pandemic period of 2020–2022, and the COVID-19 transition period of 2023–2024. The cohort included 341 patients diagnosed before the pandemic, 270 during it and 178 during the transition. Sputum smear results were available for 738 patients, or 93.5% of the cohort.

Acid-fast bacilli smear positivity was 34.4% in the pre-pandemic period, 32.0% during the pandemic and 48.6% during the COVID-19 transition. The difference across the three periods was statistically significant, with a p-value of 0.001. Multivariable logistic regression showed that the transition period was independently associated with smear positivity compared with the pre-pandemic period, yielding an adjusted odds ratio of 1.92 and a 95% confidence interval of 1.28–2.87; the association had a p-value of 0.002.

The pattern for cavitary disease differed. Its prevalence was 10.3% before the pandemic, 12.6% during the pandemic and 14.0% during the COVID-19 transition, but the differences across periods were not statistically significant, with a p-value of 0.412. Neither the pandemic nor transition period was independently associated with cavitation in the multivariable analysis. Diabetes mellitus and recurrent tuberculosis, however, were independently associated with cavitary pulmonary disease.

Taken together, the findings show a temporal change in one laboratory measure of pulmonary tuberculosis without a parallel statistical difference in the prevalence of radiographic cavitation. Because the study was retrospective, cross-sectional and based at a single medical center in southern Taiwan, it cannot establish that pandemic-era conditions caused the higher smear positivity or that the same pattern occurred nationwide. The data nevertheless identify the COVID-19 transition period as a period associated with an increase in positive sputum smears among newly diagnosed pulmonary tuberculosis patients, while also showing that the rise was not mirrored by a significant change in cavitary disease prevalence.

Subject of Research: Temporal changes in sputum acid-fast bacilli smear positivity and cavitary pulmonary disease among adults with tuberculosis in Taiwan

Article Title: Sputum acid-fast bacilli smear positivity and cavitary pulmonary disease across COVID-19 pandemic phases in Taiwan

Article References: Hsieh, C.-J., Weng, T.-P., Lu, M.-Y., Lu, C.-L., & Lee, N.-Y. (2026). Sputum acid-fast bacilli smear positivity and cavitary pulmonary disease across COVID-19 pandemic phases in Taiwan. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14631-6

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14631-6

Keywords: tuberculosis, COVID-19 transition, acid-fast bacilli, sputum smear, cavitary pulmonary disease, Taiwan, public health surveillance, retrospective study, Sputum, acid-fast, bacilli, smear