Clinical Performance of (1,3) Beta-D Glucan for the Diagnosis of Pneumocystis Pneumonia (PCP) in Cancer Patients Tested With PCP Polymerase Chain Reaction.

BACKGROUND: Serum (1,3)-beta-D glucan (BDG) is increasingly used to guide the management of suspected Pneumocystis pneumonia (PCP). BDG lacks specificity for PCP, and its clinical performance in high-risk cancer patients has not been fully assessed. Polymerase chain reaction (PCR) for PCP detection is highly sensitive, but cannot differentiate between colonization and infection. We evaluated the diagnostic performance of serum BDG in conjunction with PCP PCR on respiratory samples in patients with cancer and unexplained lung infiltrates. METHODS: We performed a retrospective analysis of adult patients evaluated for PCP at our institution from 2012 to 2015, using serum BDG and PCP PCR. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the serum BDG at different thresholds were evaluated using PCP PCR alone or in conjunction with clinical presentation in PCP PCR-positive patients. RESULTS: With PCP PCR alone as the reference method, BDG (≥80 pg/mL) had a sensitivity of 69.8%, specificity of 81.2%, PPV of 34.6%, and NPV of 95.2% for PCP. At ≥200 pg/mL in patients with a positive PCR and a compatible PCP clinical syndrome, BDG had a sensitivity of 70%, specificity of 100%, PPV of 100%, and NPV of 52.0% for PCP. CONCLUSIONS: Patients negative by both BDG and PCR were unlikely to have PCP. In patients with a compatible clinical syndrome for PCP, higher BDG values (>200 pg/mL) were consistently associated with clinically-significant PCP infections among PCP PCR-positive oncology patients.

Diagnosis of Extrapulmonary Legionellosis in Allogeneic Hematopoietic Cell Transplant Recipients by Direct 16S Ribosomal Ribonucleic Acid Sequencing and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

Identifying extrapulmonary legionellosis is difficult due to the lack of clinical suspicion and limitations of conventional microbiologic methods. We present a case series of hematopoietic cell transplant recipients with extrapulmonary legionellosis diagnosed via molecular diagnostics: 16S ribosomal ribonucleic acid gene Sanger sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.