Nonvalue of antigen detection immunoassays for diagnosis of candidemia

We evaluated the Cand-Tec (Ramco Laboratories Inc., Houston, Tex.) and LA-Candida antigen detection system (Immuno-Mycologics Inc., Norman, Okla.) tests as possible rapid alternatives to blood cultures for the identification of patients with candidemia. Tests were performed on sera from (i) 33 patients with candidemia, (ii) 82 patients with fever and risk factors for invasive candidiasis, and (iii) 13 healthy controls. A total of 21 patients had no evidence of invasive candidiasis, as determined by clinical course, blood culture, and/or autopsy; results for 61 patients were indeterminate regarding the presence of invasive candidiasis, or else the patients had invasive candidiasis with organ involvement. By using a threshold positive Cand-Tec titer of greater than or equal to 1:4, the sensitivity in candidemic patients was 49%; the specificity was 43% (patients with true-negative results had neither candidemia nor other evidence of invasive candidiasis). Coexistent disseminated candidiasis in some candidemic patients may have accounted for some positive Cand-Tec tests and possible overestimation of the sensitivity of the test for candidemia. Cand-Tec test results were negative for healthy controls. All test results obtained by the LA-Candida antigen detection system assay were negative. Our findings indicate that neither of these assays reliably identifies patients with candidemia.