Prostate specific antigen--a screening test for prostatic cancer?
A series of 287 patients referred by their family doctors with symptoms of bladder outflow obstruction were asked to attend the hospital for "pre-clinic" screening for carcinoma of prostate (CaP). Blood samples were collected from 211 patients and analysed for serum prostate specific antigen (PSA) and prostatic acid phosphatase (PAP). Thirty-six patients had a serum PSA greater than 10 micrograms/l and 7 had PAP levels greater than 5 iu/l. In no instance was the PAP elevated without an associated increase in PSA concentration. Patients with raised markers underwent further investigations which included prostatic biopsy and/or resection; 17 patients were proved to have carcinoma of the prostate, 9 of whom had distant metastases. The specificity of PSA for detecting prostate cancer in this study was 90% with a sensitivity of 89.5%, in contrast to values for PAP of 100% and 36.8%. The routine use of PAP as a marker for prostatic cancer should be abandoned. The use of PSA as a screening test in a group of patients with prostatism appears justified, but with a positive predictive value of only 47%, its use in a mass unselected screening programme is not recommended.
Powell
C S
CS
Department of Urology, Morriston Hospital, Swansea.
Fielding
A M
AM
Rosser
K
K
Ames
A C
AC
Vaughton
K C
KC
D000135:Acid Phosphatase / Q000097:blood; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000032:analysis*; D014408:Biomarkers, Tumor / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011467:Prostate / Q000032:analysis; D017430:Prostate-Specific Antigen; D011471:Prostatic Neoplasms / Q000175:diagnosis*
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D000135:Acid Phosphatase; D017430:Prostate-Specific Antigen