Comparing the Performance of Two Cryptococcal Antigen Detection Tests: Chemiluminescence vs Colloidal Gold Methods

Objective: To compare the performance of a new chemiluminescence method with that of the traditional colloidal gold method for cryptococcal antigen (CrAg) detection.

Methods: Cryptococcosis is a global invasive mycosis associated with significant morbidity and mortality. Cryptococcal antigen (CrAg) testing from serum and cerebrospinal fluid (CSF) has been regarded as the gold standard for early diagnosis. In this study, a total of 140 samples (92 serum and 48 cerebrospinal fluid samples) from 140 patients with suspected cryptococcosis collected between January 2022 and September 2023 at Zhejiang Provincial People's Hospital were tested via a fully automated chemiluminescent immunoassay analyser (SuperFlex) from Suzhou Xinbo and a cryptococcal antigen detection kit (colloidal gold method) from the IMMY Company of the United States.

Results: According to the diagnostic criteria for cryptococcosis, 55 of the 140 suspected patients were diagnosed with cryptococcosis (39.3%), including 47 with pulmonary cryptococcosis (PC) and 8 with cryptococcal meningitis (CM). The degree of agreement between chemiluminescence and the colloidal gold method was analysed via Cohen's kappa coefficient, which was 0.970 (P<0.01). The sensitivities of the chemiluminescence and colloidal gold methods were 98.2% and 96.4%, respectively, and their specificities were 100% and 98.8%, respectively. The area under the receiver operating characteristic (ROC) curve were 0.996 for chemiluminescence and 0.9759 for the colloidal gold method. The area under the curve (AUC) of the two methods did not differ significantly (P=0.086).

Conclusion: For the detection of CrAg, the new chemiluminescence method is highly consistent with the traditional colloidal gold method and has higher sensitivity and specificity for the diagnosis of cryptococcosis.