[The incidence of the variability of the free PSA/total PSA ratio on the early diagnosis of prostate cancer].
BACKGROUND
In patients with moderate elevation of total PSA, the use of the Free PSA/Total PSa ratio (F+T PSA) has been shown to be useful in the diagnosis of impalpable prostatic cancer. However, the cut-off values proposed in the literature vary from study to study and according to the immunoassay kit used. Our prospective study was designed to compare 3 different kits (Tandem, Cis Bio and Immunocorp) on the same series of patients in order to determine on the basis of these results and a review of the literature, the optimal ratio for which prostatic biopsies should be indicated in the presence of an isolated elevation of Total PSA.


METHODS
Serum samples from 141 patients (43 cancers and 98 cases of histologically confirmed BPH) were included. Assays were performed concomitantly with histological examination of the prostate, using Tandem, Cis Bio and Immunocorp kits.


RESULTS
In the overall patient population, Total PSA and Free PSA assays were statistically different for the 3 kits (p < 0.001). The F/T PSA ratio was always statistically different between the cancer and benign prostatic hyperplasia groups (p < 0.002). The cut-off values defined by a sensitivity of 90% were of 0.22 for Tandem (specificity: 27.5%), 0.34 for Cis Bio (specificity: 19.4%) and 0.26 for Immunocorp (specificity: 26.5%). When the total PSA level was between 4.0 and 10.0 ng/ml, these cut-off values also differed: 0.23 for Tandem (specificity: 26.6%), 0.35 for Cis Bio (specificity: 17.2%) and 0.25 for Immunocorp (specificity: 29.7%). In patients with a non-suspicious digital rectal examination and a F/T PSA ratio less than 0.10, the cancer detection rate (number of biopsies required to diagnose 1 cancer) was 1.66 for Tandem, 1 for Cis Bio and 1.87 for Immunocorp versus 7.7 while, when the F/T PSA ratio was greater than 0.22, the cancer detection rate was infinity (no cancer beyond this limit), 12.5 and 23, respectively.


CONCLUSIONS
The F/T PSA ratio increases the specificity of prostatic cancer detection in patients with a total PSA between 4 and 10.0 ng/ml with a non-suspicious digital rectal examination, therefore resulting in a reduction of the useless biopsy rate and defining more relevant indications for biopsies in the case of periodic follow-up. The systematic indication of this ratio in the screening context cannot be recommended, but it can be useful to demonstrate stage TIC tumours in order to avoid numerous useless biopsies.
de La Taille
A
A
Clinique d'Urologie, Hôpital d'Instruction des Armées du Val de Grâce, Paris, France.
Houlgatte
A
A
Houdelette
P
P
Berlizot
P
P
Fournier
R
R
Ricordel
I
I
D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood*; D001706:Biopsy; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010808:Physical Examination; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000473:pathology; D011933:Reagent Kits, Diagnostic; D012007:Rectum; D012016:Reference Values; D012680:Sensitivity and Specificity
D014408:Biomarkers, Tumor; D011933:Reagent Kits, Diagnostic; D017430:Prostate-Specific Antigen