934 - Diagnostic Utility of Blood (1- >3)-β-D-Glucan Testing in Patients with HIV in Arkansas

Background: Blood (1- > 3)-β-D-Glucan (BDG) is a sensitive marker for Pneumocystis jirovecii pneumonia (PJP) in patients with AIDS (PWA). However, other fungal infections, including progressive disseminated histoplasmosis (PDH), cause high levels of BDG. At our hospital, PDH is a common diagnosis in PWA with fever and respiratory complaints, making it difficult to differentiate PJP from PDH based on clinical features alone. The objective of this study was to assess BDG as a diagnostic test for PJP in Arkansas where histoplasmosis is endemic.

Methods: We performed a retrospective review of patients with confirmed PJP and confirmed PDH who had BDG testing between 2014-2020. Positive cytological or histological evidence of P. jirovecii in bronchoalveolar lavage (BAL) or lung biopsy, or positive PCR on sputum or BAL confirmed PJP. Identification of Histoplasma capsulatum in culture of blood or other normally sterile site, histology showing typical yeast forms, or a positive urine H. capsulatum antigen assay (MiraVista Diagnostics) confirmed PDH. The Fungitell Assay determined BDG levels as follows: negative, < 60 pg/mL; indeterminate, 60-79 pg/mL, and positive > 80 pg/mL.  Values below 31 pg/mL and those above 500 pg/mL were censored at 30 and 500, respectively. Respiratory symptoms were defined as the presence of cough, shortness of breath, or dyspnea on exertion.

Results: 53 episodes of PDH occurred in 46 patients. 42 were accompanied by a BDG result. Of these, 38 (90%) were positive; 3 (7%) were negative; and 1 (2%) was indeterminate. 44 (83%) of the PDH episodes were associated with respiratory symptoms. 36 of these had a BDG result. 34 (94%) were positive; 1 (3%) was negative; and 1 (3%) was indeterminate. 44 episodes of PJP occurred in 40 patients. All had a BDG result. 43 (98%) were positive.10 (23%) episodes of PJP were accompanied by a concomitant infection.
The mean BDG level was significantly higher in the PJP group compared to those with PDH and respiratory symptoms (P=.002). However, values overlapped substantially, and BDG positivity was not significantly more frequent in the PJP group (P=.586).Results of (1->3)-β-D-Glucan Testing by Diagnosis
Box-and-Whisker Display of (1->3)-β-D-Glucan Results


Conclusion: In Arkansas, BDG positivity is not a reliable marker of PJP because it cannot distinguish between PJP and PDH. Attributing an elevated BDG to PJP without additional evaluation risks misdiagnosis.