Phenotypic Atypia, Prolonged Diagnostic Delay and Altered Co-detection Patterns in Non-HIV Immunocompromised Pulmonary Tuberculosis.

BACKGROUND: Health system delay (HSD), defined as the interval from first medical contact to microbiological confirmation of pulmonary tuberculosis (PTB), may contribute to delayed diagnosis in non-HIV immunocompromised hosts (ICH). Data on HSD in this population remain limited. METHODS: This retrospective study analyzed inpatients with liquid culture-positive PTB from 2020 to 2025. Baseline characteristics, HSD, microbiological co-detection, and specimen-specific diagnostic yields were compared. HSD >14 days was defined as long health system delay (LHSD). RESULTS: Among 578 patients, 71 were ICH and 507 were non-ICH. ICH patients had atypical radiological findings, with more bilateral lesions, pleural effusion, and lymphadenopathy but fewer cavities. Median HSD was longer in ICH patients (90 vs. 24 days, p <0.001). LHSD was more frequent in ICH patients (83.1% vs. 69.2%, p =0.012), and ICH was independently associated with LHSD (adjusted OR, 2.31; 95% CI, 1.03-5.18; p =0.042). Sputum acid-fast bacilli (AFB) smear positivity was lower in ICH patients (3.4% vs. 20.0%, p = 0.055), whereas bronchoalveolar lavage fluid (BALF) AFB smear positivity was higher (51.1% vs. 28.3%, p < 0.05). Sputum, BALF, and tissue Xpert MTB/RIF positivity exceeded 75% without significant between-group differences. Fungal, viral, and mixed co-detections were more frequent in ICH patients. CONCLUSIONS: ICH patients with PTB had longer HSD and atypical radiological presentations, with more frequent fungal, viral, and mixed co-detections. Xpert testing of sputum and BALF may facilitate diagnosis, while sputum smear findings should be interpreted cautiously given its limited use in ICH patients.