BACKGROUND: Using three commercially available, unmodified PSA assays, 917 sera of 355 patients after radical prostatectomy underwent native and lyophilisation-concentrated PSA-detection to evaluate the benefit of serum concentration as a tool to increase sensitivity for earlier detection of recurrent prostate cancer after RP. MATERIALS AND METHODS: We evaluated Abbott IMX, Tosoh ALA-600 and DPC-Immulite Assay in the follow-up of 355 patients. Mean follow-up time is 374 days (43-2057). All sera underwent native analysis and 4 fold- lyoconcentration and subsequent triplicate standard analysis on each assay. Evaluation of native and concentrated sera: A PSA-value of > or = 0.10 ng/ml was positive. Sera reading <0.10 ng/ml were considered negative. In 4-fold concentrated sera this means a calculated increase of sensitivity to > or = 0.025 ng/ml. The average day of detection of a first positive signal either in native or concentrated sera for each assay was calculated as well as the time showing the average day difference of earlier detection in the lyoconcentrated sera for each assay. 20 Female sera were run and consistently read zero values in native and concentrated sera. RESULTS: In 355 patients, the number of PSA-positive patients were 58, 65 and 62 on Abbott, Tosoh and Immulite, respectively. 17/58 (29.3%), 19/65 (29.2%) and 20/62 (31.7%) patients could be identified earlier in lyoconcentrated than in native sera. A mean time advantage of 308-336 days was found. No patient who was positive according to supersensitive criteria had a negative supersensitive result, in his later follow-up. 17/19 (89.4%) patients in the Tosoh, 17/20 (85%) in the Immulite and 10/17 (58.8%) in the Abbott were identified as PSA-positive within one year after RP. CONCLUSION: PSA was positive in lyoconcentrated sera a mean of one year earlier than in native sera The maximum time advantage of lyoconcentration was 862 days, indicating PSA-recurrence 2.3 years earlier than standard analysis. 58.8-89.4% of patients with biochemical evidence of PSA-recurrence in supersensitive analysis were found within one year after RP. Lyoconcentration increases PSA-signals reliably in different assays. It can be performed as a quick routine procedure.
