Preliminary clinical evaluation of free/total PSA ratio by the IMMULITE® system

The role of free (F) and complexed serum PSA is now under investigation. In the present study, we evaluated the clinical significance of F-PSA and F/Total (T) PSA ratio in a preliminary series of samples from 88 patients with prostate cancer (PC), 113 with benign prostatic disease (BPD); and 98 with non-prostatic disease (NP). We used the F-PSA and third generation T-PSA (DPC, Los Angeles, USA) chemiluminescent enzyme immunometric assays with the IMMULITE automated system. At the 10 ng/ml cutoff for T-PSA levels, we obtained a sensitivity of 83% with a specificity of 100% in NP and 80% in BPD. The addition of the F/T ratio - rather than F-PSA levels - was useful to better discriminate PC and BPD in the cases erroneously classified by T-PSA alone: 44/68 samples (65%) were correctly diagnosed. Moreover, the F/T ratio was particularly effective in the critical T-PSA range between 4.1-9.9 ng/ml; 26/40 cases (65%) were correctly evaluated. In conclusion, the F/T ratio seems to be an interesting auxiliary test to T-PSA, to be reserved for selected cases where additional diagnostic information is necessary.