Contribution of the platelia Candida-specific antibody and antigen tests to early diagnosis of systemic Candida tropicalis infection in neutropenic adults

The Platelia Candida-specific antigen and antibody assays (Bio-Rad Laboratories) were used to test serial serum samples from seven neutropenic adult patients with hematological malignancies who had developed systemic Candida tropicalis infections. The diagnosis of candidiasis was based on a positive blood culture (all seven patients) and the isolation of C tropicalis from a normally sterile site (six patients). All patients received early antifungal therapy with amphotericin B and/or an azole derivative and had successful outcomes. When the combined assays were applied to sera collected at different time points before and after the first positive blood culture, all patients tested positive. In six patients, at least one positive test was obtained with sera collected, on average, 5 days (range, 2 to 10 days) prior to the first positive blood culture, while blood cultures were constantly negative. High and persistent mannanemias were detected in all patients during the neutropenic period. In five patients, an increased antibody response was detected when the patients recovered from aplasia. Controls consisted of 48 serum samples from 12 febrile neutropenic patients with aspergillosis (n = 4), bacteremia (n = 4), or no evidence of infection (n = 4). A low level of mannanemia was detected in only one serum sample, and none showed significant Candida antibody titers. Our data thus confirm the value of the combined detection of mannanemia and antimannan antibodies in individuals at risk of candidemia and suggest that in neutropenic patients, an approach based on the regular monitoring of both markers could contribute to the earlier diagnosis of C. tropicalis systemic infection.