The Establishment and Evaluation of Luminescent-Labelled Immunometric Assays for Prostate-Speciflc Antigen-α1-Antichymotrypsin Complexes in Serum

Prostate-specific antigen is found in the prostate in two forms, one with a low (30,000) and one with a high (100,000) relative molecular mass. The latter has recently been found to be a complex of prostate-specific antigen with alpha 1-antichymotrypsin. Immunoluminometric assays were designed for the prostate-specific antigen-alpha 1-antichymotrypsin complex as well as for alpha 1-antichymotrypsin, the former being compared with a commercially available radioimmunoassay for prostate-specific antigen (ProsChek RIA-Yang Laboratories). The precision of the immunoluminometric assays was acceptable (intra-assay variation less than 7%; inter-assay variation less than 8.5%) in the measuring ranges 0-90 micrograms/l for the prostate-specific antigen-alpha 1-antichymotrypsin complex and 0-12 g/l for alpha 1-antichymotrypsin. The correlation between the assays for prostate-specific antigen and prostate-specific antigen-alpha 1-antichymotrypsin complex was acceptable, showing a correlation coefficient r = 0.83 after double logarithmic transformation, or r = 0.85 using the Spearman rank correlation on 131 data pairs. Extremely high alpha 1-antichymotrypsin levels (above 2 g/l) caused interference in the prostate-specific antigen-alpha 1-antichymotrypsin complex assay. Such levels, although rare, are encountered in pulmonary inflammatory disease. The reference ranges for the three assays were found to be as follows: prostate-specific antigen 0.13-4.63 micrograms/l, prostate-specific antigen-alpha 1-antichymotrypsin complex 0.08-1.78 microgram/l, and for alpha 1-antichymotrypsin 0.27-0.61 g/l. These values were obtained from 82 hospitalised males for the first two assays and from 80 males and females free from infection for the latter.(ABSTRACT TRUNCATED AT 250 WORDS)