F. Espana et al., QUANTITATIVE IMMUNOASSAY FOR COMPLEXES OF PROSTATE-SPECIFIC ANTIGEN WITH ALPHA(2)-MACROGLOBULIN, Clinical chemistry, 42(4), 1996, pp. 545-550
We have developed two ELISAs for quantifying complexes of prostate-spe
cific antigen (PSA) with alpha(2)-macroglobulin (alpha(2)M), using par
tially purified PSA:alpha(2) complex as the calibrator, One ELISA was
designed to evaluate PSA:alpha(2)M complex in fluids containing a huge
excess of PSA over the amount of complex (semen-derived fluids), the
other for use in fluids containing an excess of alpha(2)M over PSA (bl
ood plasma). The range of the assays was 2-1000 mu g/L for PSA complex
ed to alpha(2)M; the detection limit was 3 mu g/L. Intra- and interass
ay CVs were 7-13% and 11-17%, respectively, at complexed PSA concentra
tions of 6-500 mu g/L. Seminal fluid from healthy men (n = 60) contain
ed 5.2 +/- 2.6 mg/L PSA complexed with alpha(2)M. Prostatic and semina
l vesicle fluids contained 6.5 +/- 2.9 and 0.3 +/- 0.2 mg/L PSA comple
xed to alpha(2)M, respectively. When purified PSA was incubated with c
itrated plasma, between 45% and 65% of the added PSA was recovered as
free PSA, whereas similar to 25% formed complexes with alpha(2)M, 10%
complexedwith alpha(1)-antichymotrypsin, and only 0.1-6% was complexed
with protein C inhibitor. Of 30 patients with prostate disease, 20 sh
owed detectable plasma PSA:alpha(2)M complexes; however, the potential
diagnostic significance of this complex requires further investigatio
n.