Measurement of circulating forms of prostate-specific antigen in whole blood immediately after venipuncture: implications for point-of-care testing.
BACKGROUND
The purpose of this study was to validate the use of whole-blood samples in the determination of circulating forms of prostate-specific antigen (PSA).


METHODS
Blood samples of hospitalized prostate cancer and benign prostatic hyperplasia patients were collected and processed to generate whole-blood and serum samples. Three different rapid two-site immunoassays were developed to measure the concentrations of total PSA (PSA-T), free PSA (PSA-F), and PSA-alpha(1)-antichymotrypsin complex (PSA-ACT) to detect in vitro changes in whole-blood samples immediately after venipuncture. The possible influence of muscle movement on the release of PSA from prostate gland was studied in healthy men by measuring the rapid in vitro whole-blood kinetics of PSA forms before and after 15 min of physical exercise on a stationary bicycle.


RESULTS
Rapid PSA-T, PSA-F, and PSA-ACT assays were designed using a 10-min sample incubation. No significant changes were detected in the concentrations of PSA-T, PSA-F, and PSA-ACT from the earliest time point of 12-16 min compared with measurements performed up to 4 h after venipuncture. Physical exercise did not influence the concentrations of the circulating forms of PSA. Hematocrit-corrected whole-blood values of PSA-T and PSA-F forms were comparable to the respective serum values. Calculation of the percentage of PSA-F (PSA F/T ratio x 100) was similar irrespective of the sample format used, i.e., whole blood or serum.


CONCLUSIONS
We found that immunodetectable PSA forms are likely at steady state immediately after venipuncture, thus enabling the use of anticoagulated whole-blood samples in near-patient settings for point-of-care testing, whereas determinations of PSA (e.g., PSA-T, PSA-F, or PSA-ACT) performed within the time frame of the office visit would provide results equivalent to conventional analyses performed in serum.
The Finsen Laboratory af.sn. 8621, Strandboulevarden 49, 2100 Copenhagen, Denmark.
T
T
Piironen
M
M
Nurmi
K
K
Irjala
O
O
Heinonen
H
H
Lilja
T
T
Lövgren
K
K
Pettersson
D001800:Blood Specimen Collection; D005080:Exercise Test; D006801:Humans; D007118:Immunoassay; D008297:Male; D019095:Point-of-Care Systems; D017430:Prostate-Specific Antigen / Q000097:blood* / Q000378:metabolism; D011470:Prostatic Hyperplasia / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood; D011485:Protein Binding; D015203:Reproducibility of Results; D000514:alpha 1-Antichymotrypsin / Q000378:metabolism
D000514:alpha 1-Antichymotrypsin; D017430:Prostate-Specific Antigen