Ratio of prostate specific antigen minor molecular forms-to-total prostate specific antigen is constant regardless of the pathological condition of the prostate.
OBJECTIVE
We assessed 3 molecular forms of prostate specific antigen (PSA) prospectively to determine the real proportion of the nonfree, nonalpha1-antichymotrypsin complex form of PSA-to-total PSA and evaluated the clinical significance of its various forms.


METHODS
We prospectively assessed 1,878 serum samples from 994 subjects for total PSA, free PSA and PSA-alpha1-antichymotrypsin complex (ACT). Nonfree, nonPSA-ACT PSA (minor form PSA) was calculated as the difference between total PSA and the sum of free PSA plus PSA-ACT complex.


RESULTS
The proportion of the minor form PSA was approximately 20% to 25% of total PSA at any range of total PSA, whereas that of free PSA and PSA-ACT decreased and increased, respectively, in correlation with the increment of total PSA. There was no significant difference in the percent of minor form PSA in patients with prostatic carcinoma and those with benign prostatic status. The proportion of minor form PSA was constant, while the percent of free PSA and PSA-ACT increased and decreased, respectively, in accordance with total PSA regression after hormonal therapy for prostatic carcinoma. PSA-ACT was judged to be superior to total PSA for distinguishing prostatic carcinoma in men with PSA 2 to 10 ng./ml. by ROC analysis.


CONCLUSIONS
Approximately a fourth of total PSA consists of minor forms of complexed PSA. The average proportion of minor form-to-total PSA was constant at various levels of total PSA and at any prostatic status of patients. PSA-ACT was superior to total PSA for the early detection of prostatic carcinoma.
Kobayashi
Takashi
T
Department of Urology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Kamoto
Toshiyuki
T
Isogawa
Yoshiaki
Y
Kinoshita
Hidefumi
H
Terai
Akito
A
Habuchi
Tomonori
T
Ogawa
Osamu
O
Kamato
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood*; D002277:Carcinoma / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood*; D011469:Prostatic Diseases / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*; D012372:ROC Curve; D012680:Sensitivity and Specificity; D000514:alpha 1-Antichymotrypsin / Q000097:blood*
D014408:Biomarkers, Tumor; D000514:alpha 1-Antichymotrypsin; D017430:Prostate-Specific Antigen