Evaluation of enzyme immunoassay for Candida cytoplasmic antigens in neutropenic cancer patients

Abstract

A Candida albicans cytoplasmic antigen enzyme immunoassay (CACP antigen EIA) was developed with antibodies raised against antigens prepared from yeast cells grown under standardized growth conditions. The C. albicans components reactive in the EIA were shown to be predominantly proteins with associated carbohydrates. Denaturing gel electrophoresis revealed the presence of five major CACP proteins with molecular weights between 36,000 and 44,000. The clinical usefulness of the CACP EIA was evaluated by retrospective blinded measurement of 89 serum samples from 31 granulocytopenic patient episodes. Twice-weekly surveillance cultures, sequential serum samples (approximately once per week or with change of the clinical course), and standard diagnostic criteria of fungal infection were used to categorize patients. The sensitivity and specificity of the CACP assay on the basis of serum samples were 82 and 100%, respectively (67 and 100% on the basis of patient episodes). The positive and negative predictive values were 100 and 97% for serum (100 and 93% for patient episodes). By comparison, the CANDTEC assay had low sensitivity (33%) and poor positive predictive values (50%). The CACP EIA may be a useful test suitable for further evaluation as a method for the diagnosis of invasive Candida infection in neutropenic cancer patients.