PURPOSE: We validated our ultrasensitive prostate specific antigen (PSA) assay based on lyophilization and 4-fold concentration of patient sera with the clinical long-term followup and according to histopathological characteristics of 422 patients treated with radical retropubic prostatectomy for prostate cancer. MATERIALS AND METHODS: Each serum sample was divided into 2 aliquots for standard and 4-fold concentrated (ultrasensitive) detection. Samples were analyzed by the same unmodified DPC-Immulite PSA assay. Biochemical relapse was defined as an increase of at least 0.10 ng./ml. in native serum (equivalent to 0.025 ng./ml. in concentrated serum). Mean followup was 449 days (range 29 to 2,057). Kaplan-Meier analysis of standard and ultrasensitive detection results was done, and findings were correlated with pathological stage, Gleason grade, total cancer volume, Gleason grade 4 cancer volume and margin status. Significance of earlier detection in ultrasensitive versus standard detection was calculated with the log rank (Mantel-Cox) test with p
