β-D-glucan and S-adenosylmethionine serum levels for the diagnosis of Pneumocystis pneumonia in HIV-negative patients: a prospective study.

Objective: To prospectively assess the diagnostic utility of S-adenosylmethionine (AdoMet) and (1→3)-β-D-glucan (β-D-glucan) serum markers for Pneumocystis pneumonia (PCP) in HIV-negative patients.

Methods: HIV-negative, immunocompromised patients suspected of PCP based on clinical presentation and chest imaging were included. PCP was confirmed or rejected by results of direct microscopy and/or real-time PCR on broncho-alveolar lavage (BAL) fluid. Measurement of serum β-D-glucan and AdoMet was performed on serum samples collected at enrollment and during follow-up. Both serum β-D-glucan and AdoMet were assessed for diagnostic accuracy and correlation with clinical and laboratory parameters.

Results: In 31 patients enrolled (21 PCP-positive, 10 PCP-negative), AdoMet levels did not discriminate between patients with and without PCP. Elevated serum β-D-glucan was a reliable indicator for PCP with a sensitivity of 0.90 and specificity of 0.89 at the 60 pg/ml cut-off. In PCP-positive patients β-D-glucan serum levels decreased during treatment and inversely correlated with Pneumocystis PCR cycle threshold values in BAL fluid.

Conclusions: The level of β-D-glucan--but not AdoMet--was diagnostic for PCP within the clinical context and may serve as marker for pulmonary fungal load and treatment monitoring.