Combined serum (1,3)-β-D-Glucan and Oral Wash PCR as a non-invasive diagnostic strategy for early detection of Pneumocystis jirovecii pneumonia: an observational retrospective study

Background The diagnosis of P. jirovecii pneumonia (PJP) in immunosuppressed, HIV-negative patients is often limited by the inability to perform a bronchoalveolar lavage (BAL) due to respiratory insufficiency. In this study, we evaluated the diagnostic accuracy of combining serum beta-D-glucan (BDG) testing with P. jirovecii PCR in oral wash (OW) samples as non-invasive tools for PJP diagnosis. Methods This was a retrospective, single-center study including all immunosuppressed non-HIV adult patients with suspected PJP in whom a Fujifilm Wako β-glucan test BDG and BAL PJ in-house PCR determination were performed during a 5-year period (2019-2024). The diagnostic performance [negative predictive value (NPV), positive predictive value (PPV), and accuracy] of BDG alone, OW PJ PCR alone and combined with OW PJ PCR, when available, was assessed in patients with PJP. PJP diagnosis was established according to EORTC/MSGERC 2021 criteria. Results One hundred and fourteen patients were included. PJP was confirmed in 15 patients (13.2%), of whom 14 had a positive BDG determination [median, IQR 55.32 pg/mL (19.98-137.90)]. BDG PPV was low (51.7%), but the overall accuracy (87.7%) for PJP diagnosis was good. Forty-seven (41%) patients had an OW performed, 11 of them diagnosed with PJP. The combined use of BDG and OW PJ PCR showed a high PPV (100%) and NPV (97.3%) and an excellent diagnostic accuracy (97.9%) for PJP diagnosis in this patient subset. Conclusions The additional use of OW PJ PCR to BDG should be considered as an accurate non-invasive combined diagnostic strategy for PJP diagnosis.