The diagnosis of
invasive candidiasis was attempted by detection of circulating
mannan antigen by using an
avidin-
biotin-amplified
enzyme-linked
immunosorbent assay (AB-ELISA), and this method was compared with the conventional culture method.
Mannan antigen was detected by AB-ELISA in the sera of 16 (84.2%) of the 19 patients with
invasive candidiasis. On the other hand, for 34 immunocompromised
candidiasis-free patients, including 8 with
aspergillosis or
cryptococcosis,
mannan antigen was positive during only 1 of the 67 febrile episodes and in the serum of none of the 50 outpatients without
infections. The results were also negative for all patients with deep-seated
mycoses other than
candidiasis. However, the
mannan level was low (less than 2.0 ng/ml) in the serum of 63.2% of the patients with
invasive candidiasis. The positivity rate of blood cultures was 31.6%, and that of blood cultures and/or cultures of samples from sterile sites combined was 47.4%. The advantages of the diagnosis based on
antigen detection by AB-ELISA are considered to be a higher sensitivity and elimination of nonspecific reactions by the introduction of the
avidin-
biotin system and pretreatment of sera by heating. In addition, it is considered essential for high sensitivity that transient
mannan antigenemia be determined frequently so that it is not overlooked. In light of its sensitivity and specificity, this method is considered to be clinically useful in the diagnosis of
invasive candidiasis.