837. Performance of Blood (1- >3)-β-D-Glucan in People with AIDS Presenting with Respiratory Symptoms

Abstract

Abstract Background The gold standard for diagnosis of Pneumocystis jirovecii pneumonia (PCP) is direct visualization of the microorganism in respiratory samples, usually obtained via bronchoalveolar lavage (BAL). Blood β-D-glucan (BDG) is used as a non-invasive adjunctive diagnostic test for PCP, but specificity is only modest, in part because other opportunistic fungal infections cause high BDG. We previously showed BDG-positivity in 94% of people with AIDS (PWA), progressive disseminated histoplasmosis (PDH), and respiratory symptoms in our hospital. In this study, we aim to assess the performance of BDG as a diagnostic test for PCP in PWA who have respiratory symptoms. Methods We retrospectively identified PWA who had a BDG result between 2014 and 2019. AIDS was defined as past or current absolute CD4 count < 200 cells/µL, or a past or current AIDS-defining condition. Positive cytological or histological evidence of P. jirovecii in bronchoalveolar lavage (BAL) fluid or lung biopsy, or positive Pneumocystis PCR on sputum or BAL confirmed PCP. The Fungitell Assay (Associates of Cape Cod, East Falmouth, MA) determined BDG levels as follows: negative, < 60 pg/mL; indeterminate, 60-79 pg/mL, and positive, ≥ 80 pg/mL. Values < 31 pg/mL and those >500 pg/mL were censored at 30 pg/mL and 500 pg/mL, respectively. Respiratory symptoms were defined as cough, dyspnea, chest pain, or hypoxia. We compared BDG results for participants with proven PCP and participants without proven PCP. Results We identified 260 PWA with a BDG result, of whom 183 had at least one respiratory symptom. 84 (45.9%) of these participants had a positive BDG. BDG results among participants with and without PCP are shown in Table 1. Of the 44 participants with a positive BDG who did not have PCP, 29 (65.9%) had PDH. Other diagnoses included cryptococcosis and candidemia. The test performance of BDG for the diagnosis of PCP is shown in Table 2. Exclusion of participants with PDH increased the specificity of BDG for PCP to 86.4%. Table 1. Results of (1->3)-β-D-glucan Testing by Pneumocystis jirovecii Pneumonia Diagnosis Among Participants with AIDS and Respiratory Symptoms Table 2. Test Performance of (1->3)-β-D-glucan for the Diagnosis of Pneumocystis jirovecii Pneumonia* Conclusion At our center where histoplasmosis is endemic, a positive BDG should not be attributed to PCP among PWA with respiratory symptoms because of low specificity and low positive predictive value. However, a negative BDG can exclude PCP in this population. Disclosures All Authors: No reported disclosures