Combined detection of mannanaemia and antimannan antibodies as a strategy for the diagnosis of systemic infection caused by pathogenic Candida species

A novel strategy for the diagnosis of systemic candidosis was evaluated, based on the combination of two enzyme immunoassays that detect a candida oligomannoside repetitive epitope expressed in large amounts by Candida albicans (Platelia Candida Ag), and antibodies against C. albicans mannan, the major cell-wall immunogen in which this epitope is present (Platelia Candida Ab). Sera were selected retrospectively from intensive care and haematology patients with clinically suspected systemic candidosis, and from whom Candida spp. had been isolated from normally sterile sites. Of the 21 patients infected with C albicans, 13 had positive antigenaemia and 14 had a positive antibody response, including eight patients who were antigenaemia negative. The sensitivity of the combined tests was 100%. In patients infected with C glabrata (n = 12) or C. tropicalis (n = 10), the sensitivity was 83% and 80%, respectively. For the remaining patients, infected with C parapsilosis (n = 10), C. krusei (n = 8) or C kefyr (n = 2), the sensitivity of the combined tests was 40%, 50% and 50%, respectively. At least one of the serological tests was positive before yeast growth occurred in 60% of patients for whom a serum sample was available before blood culture sampling. An increase in serological test positivity to >80% was observed for sera obtained around the date of positive culture, irrespective of the Candida species isolated. These results suggest that regular serological monitoring for both mannanaemia and anti-mannan antibodies in at-risk patients may contribute to the early diagnosis of candidosis.