Metagenomic next-generation sequencing for pneumocystis jirovecii pneumonia in patients with connective tissue disease

BackgroundAccurate diagnosis of Pneumocystis jirovecii pneumonia (PJP) is challenging, and the delayed diagnosis of PJP is associated with high mortality in patients with connective tissue disease (CTD). Metagenomic next-generation sequencing (mNGS) technology facilitates etiological diagnosis of various infectious diseases, with promising application in diagnosing PJP. This study aimed to investigate the value of mNGS using bronchoalveolar lavage fluid (BALF) for diagnosing PJP infection. MethodsData from 55 patients with CTD and suspected pulmonary infection was retrospectively collected and analysed. A PJP group and non-PJP group were formed. The clinical manifestations, laboratory test results, treatment methods, and outcomes were summarized. BALF mNGS results were compared with traditional pathogen tests (TPT) and serum 1,3-beta-D-glucan (BDG) testing. ResultsThe mean age of PJP patients was 54 years, and 59% (10/17) of the patients were female. A significant difference was found between the average daily dose of prednisone administered to the PJP group and non-PJP group (25 mg vs. 16 mg, P < 0.001). The PJP group had a significantly higher incidence of dyspnoea (88% [15/17] vs. 16% [6/38], P < 0.001) and elevated serum BDG level (167.73 vs. 30.67 pg/mL, P < 0.001). BALF mNGS was more sensitive than both TPT (100% [95% confidence interval {CI}: 77.1%-100%] vs. 11.8% [95% CI: 2.1%-37.7%], P < 0.001) and serum BDG (100% [95% CI: 77.1%-100%] vs. 85.7% [95% CI: 42%-99.2%], P < 0.001). BALF mNGS was more specific than serum BDG (89.5% [95% CI: 74.3%-96.6%] vs. 46.7% [95% CI: 22.3%-72.6%], P = 0.493). Co-infection with cytomegalovirus (CMV) was more common in the PJP patients than in the non-PJP patients (59% [10/17] vs. 11% [4/38], respectively, P < 0.001). ConclusionBALF mNGS technology is highly effective for diagnosing PJP in patients with CTD and identifying co-infections.