Metagenomic next-generation sequencing performed on blood samples for the early recognition of severe Pneumocystis pneumonia in critical hematological patients.

Severe Pneumocystis pneumonia (PCP) has a poor prognosis, and its early and precise diagnosis is difficult in immunocompromised individuals. Therefore, this study explored the diagnostic value of metagenomic next-generation sequencing (mNGS) of peripheral blood in diagnosing severe PCP in patients with hematological diseases. This prospective study analyzed the clinical manifestations, mNGS results (from the peripheral blood), traditional pathogen detection results, laboratory test results, chest computed tomography (CT) images, treatments, and outcomes of severe PCP in hematological patients who were hospitalized in the 2 centers of the Affiliated Hospital of Soochow University between September 2019 and October 2021. A total of 31 cases of hematological diseases complicated with pulmonary infections, including 7 cases of severe PCP diagnosed by mNGS performed on peripheral blood samples, were analyzed. Traditional pathogen detection methods for PCP cannot be used. In contrast, the laboratory readings for Pneumocystis jirovecii (Pj) detected within 48 hours of symptom onset by mNGS on the 7 blood samples ranged from 12 to 5873, with a median value of 43. Under the guidance of the mNGS results, preemptive antimicrobial therapy with trimethoprim/sulfamethoxazole alone or in combination with caspofungin was administered to treat Pj. After treatment, 4 patients recovered, and 3 patients died of acute respiratory failure and acute respiratory distress syndrome (ARDS). MNGS performed on peripheral blood samples is optional but can provide early recognition of severe PCP and help guide empirical treatment in critical hematological patients.