Variations in prostate-specific antigen free total ratio in acute stress

Serum prostate-specific antigen complexed to alpha2-macroglobulin is occult and is not detected by conventional immunoassays. Conditions affecting alpha2-macroglobulin levels may alter the specificity of prostate-specific antigen free total ratio in predicting prostate cancer. A group of patients (n = 24) undergoing surgical stress due to a coronary artery bypass grafting was followed pre- and postoperatively up to 6 days. Total and free prostate-specific antigen, alpha2-macroglobulin, and C-reactive protein were measured by electrochemiluminescence, immunonephelometry, and immunoturbidimetry, respectively. Total prostate-specific antigen and C-reactive protein increased significantly postsurgery and remained elevated. Free total ratio correlated negatively with C-reactive protein only (p = 0.000) using xtgee panel data analysis, after correction for plasma volume changes using albumin. Increased C-reactive protein may reflect falsely decreased free total ratio. Therefore, prostate-specific antigen free total ratio would be more reliable if interpreted in combination with information about CRP. However, it is recommended to defer the measurement of free total ratio if CRP is highly elevated.