In light of recent studies showing that prostate-specific antigen (PSA
) complexes with certain blood proteins, we studied the effects of acu
te-phase reactants and alpha(2)-macroglobulin (A2MG) on serum concentr
ations of PSA. Serum samples were obtained from 419 men admitted to an
acute-care facility. Various acute-phase reactants-including C-reacti
ve protein, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, and alph
a(1)-antichymotrypsin-and A2MG were measured with a Beckman Array(R) a
nalyzer in parallel with determinations of PSA concentrations by two m
ethods, the Hybritech Tandem(R) RIA. and the Abbott PSG IMx(R). Evalua
tion by Spearman rank correlation revealed a significant negative corr
elation of A2MG with PSA values (P <0.01) and (as expected) a positive
correlation of age with PSA values (P <0.001). The former correlation
suggests the possibility that patients with high serum concentrations
of A2MG may give falsely decreased results for PSA concentrations in
serum.