Using the free-to-total prostate-specific antigen ratio to detect prostate cancer in men with nonspecific elevations of prostate-specific antigen levels.
BACKGROUND
Prostate-specific antigen (PSA) levels between 4.0 to 10.0 ng/ml have poor specificity in prostate cancer screening, leading to unnecessary biopsies.


OBJECTIVE
To determine whether the free-to-total PSA ratio (F/T PSA) improved the diagnostic accuracy of these nonspecific PSA levels.


RESULTS
MEDLINE searchedwas from 1986 to 1997. Additional studies were identified from article bibliographies and by searching urology journals. Two investigators independently identified English-language studies providing F/T PSA ratio test-operating characteristics data on > or = 10 cancer patients with PSA values between 2.0 and 10.0 ng/ml. Twenty-one of 90 retrieved studies met selection criteria. Two investigators independently extracted data on methodology and diagnostic performance. Investigator-selected cut points for the optimal F/T PSA ratio had a median likelihood ratio of 1.76 (interquartile range, 1.40 to 2.11) for a positive test and 0.27 (0.20 to 0.40) for a negative test. Assuming a 25% pretest probability of cancer, the posttest probabilities were 37% following a positive test and 8% following a negative test. The summary receiver operating characteristic curve showed that maintaining test sensitivity above 90% was associated with false positive rates of 60% to 90%. Methodologic problems limited the validity and generalizability of the literature.


CONCLUSIONS
A negative test reduced the posttest probability of cancer to approximately 10%. However, patients may find that this probability is not low enough to avoid undergoing prostate biopsy. The optimal F/T PSA ratio cut point and precise estimates for test specificity still need to be determined.
Hoffman
R M
RM
Medicine Service, Albuquerque Department of Veterans Affairs Medical Center, NM 87108, USA. rhoffman@unm.edu
Clanon
D L
DL
Littenberg
B
B
Frank
J J
JJ
Peirce
J C
JC
D003627:Data Interpretation, Statistical; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*; D012680:Sensitivity and Specificity
D017430:Prostate-Specific Antigen