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

Background:Accurate 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.Methods:Data 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.Results:The 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).Conclusion:BALF mNGS technology is highly effective for diagnosing PJP in patients with CTD and identifying co-infections.