Evaluation of routine screening for early detection of Histoplasma and Cryptococcus antigens in CD4-referred blood specimens in Colombia: A prospective study of prevalence and geographic distribution.

Histoplasmosis and cryptococcosis are major opportunistic infections among patients who are immunosuppressed. This prospective study evaluates the utility of routine antigen screening for Histoplasma and Cryptococcus in patients referred for CD4 count testing at Synlab, Medellin, Colombia. A total of 323 plasma specimens with CD4 counts < 500 cells/µl collected between November and December 2024 were analyzed using commercial antigen detection assays. Overall, 4% of specimens were positive for one of the antigens tested, 2% for each pathogen. Many of the positives were detected in samples with CD4 > 200, demonstrating the need to screen patients above this threshold. The geographical distribution of positives could suggest the value of regionalized screening strategies. Our findings support the integration of early antigen screening into routine care of patients with immunosuppression.