Detection of circulating capsular polysaccharide antigen from Cryptococcus neoformans.

In their paper entitled "Comparison of the PREMIER Cryptococcal Antigen Enzyme Immunoassay and the Latex Agglutination Assay for Detection of Cryptococcal Antigens" (1), Gade et al. compare a new enzyme immunoassay (EIA) for the detection and quantification of circulating capsular polysaccharide antigen from Cryptococcus neoformans with the latex agglutination (LA) test performed with a commercially available kit, the CALAS LA test (Meridian Diagnostics). In the Discussion, the authors conclude that "PREMIER appears to have a 12-fold sensitivity advantage over LA," which is indeed supported by their experimental data. In our opinion, this sentence should be modified to read as follows: "PREMIER appears to have a 12-fold sensitivity advantage over the CALAS LA test," since it is well known that the sensitivity of the LA test varies from one kit to another. In their comparative study, the authors have chosen a latex kit which, in our experience, is much less sensitive than, e.g., the IMMY kit from Immuno-Mycologics. In our laboratory, the IMMY has been used for years on several hundreds of specimens. It is also our standard for the evaluation of the value of other antigen detection kits. We would like to suggest that they compare their new ETA kit, which possibly is better than any latex kit, with a more sensitive LA test, such as the IMMY kit from Immuno-Mycologics.