Diagnosis of systemic candidiasis by latex agglutination for serum antigen

Three latex agglutination test procedures for detecting Candida antigen in human serum were compared in a retrospective study of 69 patients and 20 normal volunteers. Untreated human serum was reacted with two different latex reagents; one reagent also was reacted with serum treated with protease and heat. The test procedure with treated serum was best, detecting serum antigen in 17 of 21 patients (81%) with disseminated candidiasis. Judging by autopsy-proven cases, there was an increase in positive test results in the last 2 weeks of life. When untreated sera were tested with this reagent, only 3 (14%) of the 21 patients with disseminated candidiasis had detectable antigen in serum. A subset of these same sera was tested by a commercial latex reagent (Candida Detection System lot C001; Ramco Laboratories, Inc., Houston, Tex.) and untreated serum. Of 18 patients with disseminated candidiasis, 5 (28%) had at least one positive serum. Sera from patients with less severe clinical forms of candidiasis were usually negative regardless of the test procedure used. With one exception, sera from control patients were negative or were positive only in sera containing rheumatoid factor. Latex agglutination tests for Candida spp. in treated serum may prove to be a useful procedure for the rapid diagnosis of severe disseminated candidiasis.