Diagnostic Value of Cryptococcal Glucuronoxylomannan Antigen Testing of Bronchoalveolar Lavage Fluid for Pulmonary Cryptococcosis in Immunocompetent Patients: A Clinical Study.

Background: [No revision is required.]Pulmonary cryptococcosis (PC) is common in immunocompetent patients, and its early diagnosis is challenging. Multiple studies have addressed the detection of cryptococcal glucuronoxylomannan (GXM) antigen in serum, but few have investigated its detection in bronchoalveolar lavage fluid (BALF).

Objectives: To evaluate the diagnostic value of the Cryptococcus GXM antigen test in BALF for PC in immunocompetent patients.

Design: We collect the clinical data of 138 patients from October 2018 to March 2023 and divide them into a PC group (n = 48) and a non-PC group (n = 90). Perform serum and BALF GXM antigen test on all cases that meet the inclusion criteria.

Methods: To analyze and compare the clinical characteristics of the PC group and non-PC group. We calculate the positive detection rate (PDR) and negative predictive value of BALF and serum GXM antigen tests, as well as their combination, for the PC group.

Results: Most patients in the PC group are male (59.6%), with an average age of 49.4 years. Most of the patients have no underlying disease (51.9%). Diabetes and hypertension are the most common comorbidities. Most patients (53.8%) are asymptomatic. Cough and sputum are the most frequent clinical symptoms, followed by fever and chest distress. Nodules and exudative consolidation are the most common imaging findings, and the culture positivity rate is 25%. Forty patients are positive according to the BALF GXM test, for a positivity rate of 83.3% and a negative predictive value of 91.8%. Moreover, 39 patients are positive according to the serum GXM test, for a positivity rate of 81.3% and a negative predictive value of 90.9%. The positivity rate for serum plus BALF is 95.8%. There is no significant difference (P > 0.05) in diagnostic value between BALF and serum GXM tests for PC. GXM positivity rates differ significantly among paired BALF, serum, and BALF plus serum groups (P < 0.05).

Conclusion: The BALF GXM test is useful for the early diagnosis of PC in immunocompetent patients. Simultaneous BALF and serum GXM testing would increase the rate of early PC diagnosis in immunocompetent patients.