Do the values of prostate specific antigen obtained from fresh and dried urine reflect the serum measurements?

AIM: To investigate if free PSA (fPSA) and total PSA (tPSA) values obtained from simultaneously collected urine, fresh and dried on filter paper, reflect the serum free and total PSA. MATERIALS AND METHODS: The sera and 20 cc first voided urine from 33 consecutive men aged between 40 and 84 (mean 61 ± 12), were collected in the morning and delivered to the laboratory. Three different aliquots of 100 microgram urine were taken with automatic pipette and dropped on 3 certain areas of a filter paper and allowed to dry for each patient. On each paper, borders of dried urine were marked. PSA values were obtained from the sera and fresh urine samples and recorded. Later on particular days dried urine samples were dissolved and eventually PSA values were derived and recorded again. The results were compared to each other. Correlations were evaluated by using an SPSS statistics program. RESULTS: Serum PSA values correlated weakly (r < 0.24) with fresh and dried urine PSA values. While PSA in fresh and dried urine samples showed strong correlation (0.5 < r < 0.74), a very strong correlation (r > 0.75) among PSA values of dried urine samples of 1-day, 7- and 28-days, were seen. CONCLUSIONS: We conclude that PSA values obtained from fresh and dried urine could not reflect serum PSA values. But, because dried urine on a filter paper can be stable for years, it could be used for forensic purposes.