mNGS and Serum G Test in Distinguishing between Pneumocystis Jirovecii Colonization and Infection: Value Comparison and Correlation Analysis

Background Pneumocystis jirovecii (PJ) can colonize the lungs, and cause pulmonary infections. It is essential to distinguish between PJ colonization and infection in the lung to avoid clinical overtreatment and delayed treatment. Many studies have shown that both the mNGS technique and serum G test can be used to aid the diagnosis of PJ pneumonia, but it is still unclear whether they have the appropriate cut-off value to distinguish PJ colonization from PJ infection. Objective To investigate the values of mNGS of alveolar lavage fluid and serum G test in distinguishing between infection and colonization of PJ and to assess the correlation between them. Methods A retrospective study design was used. Forty inpatients with pulmonary infections were recruited from Hubei No.3 People's Hospital of Jianghan University from September 2018 to May 2022, and divided into PJ infection group (n=21) and colonization group (n=19), according to the prevalence of anti-PJ treatment based on mNGS results of alveolar lavage fluid. Clinical data were collected, including general information〔gender, age, BMI, smoking history, underlying diseases (chronic kidney disease, hematological diseases, autoimmune diseases, malignancy, HIV, solid organ transplantation, chronic lung disease, the use of glucocorticoid/immunosuppressive agents) 〕, clinical symptoms (fever, cough, phlegm, dyspnea, chest pain, hemoptysis), imaging features (ground-glass shadow, interstitial change, consolidation, nodule, pleural effusion, cyst), laboratory indicators (white blood cell count, neutrophil count, lymphocyte count, PCT, CRP, LDH, PaO2/FiO2, CD4+T lymphocytes). The receiver operating characteristic (ROC) curve of mNGS and serum G test was plotted and analyzed to assess their performance in distinguishing between PJ infection and colonization, and the correlation between the two was analyzed. Results The utilization rate of glucocorticoids or immunosuppressants in PJ infection group was higher than that of colonization group (P