Although kits to detect cryptococcal antigen are used widely to diagno
se cryptococcal infection, the comparative performance of commercially
available assays has not been evaluated in the past decade. Therefore
, we compared the sensitivities and specificities of five commercially
available kits for detecting cryptococcal antigen (four latex aggluti
nation test kits-Calas [Meridian Diagnostics]), Crypto-LA [Internation
al Biological Labs], Myco-Immune [MicroScan], and Immy [Immunomycologi
cs]-and an enzyme immunoassay kit, Premier [Meridian Diagnostics]) wit
h culture for the diagnosis of cryptococcal meningitis and fungemia. O
f 182 cerebrospinal fluid (CSF) and 90 serum samples submitted for cry
ptococcal antigen and fungal culture, 49 (19 and 30 samples, respectiv
ely) from 20 patients had a culture positive for Cryptococcus neoforma
ns. For CSF specimens, the sensitivities and specificities of all kits
were comparable (sensitivity, 93 to 100%; specificity, 93 to 98%). Th
ere was a significant difference in sensitivities of the kits when ser
um samples were tested with the international Biological Labs and Micr
oScan kits, which do not pretreat serum with pronase. These kits were
less sensitive (sensitivity, 83%) than the Immy and Meridian latex kit
s (sensitivity, 97%), which do pretreat with pronase. The sensitivity
of the Meridian enzyme immunoassay kit was comparable to that of the p
ronase-containing latex kits. These kits were of equivalent specificit
ies (93 to 100%) when testing serum. Some of the currently available k
its have limitations that need to be recognized for proper interpretat
ion of results. Specifically, the use of pronase on serum samples redu
ces the number of false-positive results, and a titer of less than or
equal to 1:4 can be a false-positive result when CSF samples are being
tested.