Diagnostic Performance of Bronchoalveolar Lavage Fluid Metagenomic Next‑generation Sequencing versus Conventional Microbiological Tests in Immunocompromised and Immunocompetent Patients with Pulmonary Infection.

PURPOSE: Pulmonary infection in immunocompromised patients is challenging to diagnose. This study evaluated the detection performance of bronchoalveolar lavage fluid (BALF) metagenomic next-generation sequencing (mNGS) in these patients. PATIENTS AND METHODS: A total of 86 patients with confirmed pulmonary infection (48 immunocompromised, 38 immunocompetent) were retrospectively enrolled. BALF samples were tested by both mNGS and conventional microbiological tests (CMTs). Pathogen detection rates and pathogen spectrum were compared between the two groups. RESULTS: The positive rate of mNGS was significantly higher than that of CMTs in overall patients (87.21% vs 50.00%, P < 0.001), with a more prominent advantage in the immunocompromised group (97.92% vs 43.75%, P < 0.001). Detection rates of fungi (39.58% vs 5.26%, P < 0.001) and viruses (54.17% vs 28.95%, P = 0.018) were significantly higher in the immunocompromised group. Opportunistic pathogens including Pneumocystis jirovecii, cytomegalovirus, and Epstein-Barr virus were detected exclusively in the immunocompromised group. The mixed infection rate was also significantly higher in this group (72.92% vs 36.84%, P < 0.001). CONCLUSION: BALF‑mNGS is a reliable supplementary tool for conventional detection. It effectively identifies missed opportunistic pathogens and complex mixed infections, especially in immunocompromised patients. Combined application of mNGS and conventional tests improves pathogen detection and may help inform anti-infective treatment decisions.