Pulmonary function impairment patterns and their clinical correlates in patients with pulmonary tuberculosis complicated by pulmonary infection: a single-center retrospective cross-sectional study.

Background and Objective: Pulmonary tuberculosis is a major cause of respiratory morbidity worldwide, and pulmonary function impairment is increasingly recognized as an important consequence of the disease. However, the functional patterns of pulmonary impairment in patients with pulmonary tuberculosis complicated by pulmonary infection, especially in hospitalized populations, remain insufficiently characterized. This study aimed to describe pulmonary function impairment patterns in such patients and to explore their clinical correlates. Methods: This single-center retrospective cross-sectional study included hospitalized patients with pulmonary tuberculosis complicated by pulmonary infection who were admitted between November 2024 and October 2025, underwent bronchoalveolar lavage fluid metagenomic next-generation sequencing, and had interpretable pulmonary function results. The analysis was retrospective because all study variables were extracted from pre-existing hospitalization records and database entries rather than being prospectively collected for the present pulmonary function study. Although the parent project is an ongoing prospective study with follow-up, no longitudinal follow-up data were used in the present analysis. Clinical, laboratory, immunologic, gas-exchange, microbiological, and pulmonary function data were extracted from the institutional database and electronic medical records. Results: A total of 72 patients were included. Pulmonary function abnormalities were common. Diffusion impairment was the most frequent phenotype, occurring in 37 patients (51.4%), followed by reduced respiratory reserve in 36 (50.0%) and obstructive ventilatory impairment in 30 (41.7%). Restrictive ventilatory impairment, mixed ventilatory impairment, and small airway dysfunction were less common. Patients with diffusion impairment were more likely to be male than those without diffusion impairment (73.0% vs. 42.9%, Conclusion: Pulmonary function impairment was highly prevalent in patients with pulmonary tuberculosis complicated by pulmonary infection, with diffusion impairment and reduced respiratory reserve as the predominant phenotypes. These findings suggest that pulmonary dysfunction in this population extends beyond conventional ventilatory defects and may involve substantial abnormalities in gas transfer and respiratory capacity. Comprehensive pulmonary function assessment may provide clinically relevant information for functional evaluation and individualized management in this patient group.