Digital rectal examination impact on PSA derivatives and prostate biopsy triggers: a contemporary study

Abstract

Objective: To evaluate the impact of the digital rectal exam (DRE) on PSA measurements and clinical decision-making.

Methods: Healthy male volunteers between 50 and 70 years old were recruited during a 30-day public screening program. PSA levels were measured using two different methods (standard enhanced chemiluminescence immunoassay-ECLIA, and novel immunochromatography assay-ICA/rapid PSA) in the same blood sample. Two blood samples were drawn; first before DRE and the second 30-40 min after DRE. The effect of DRE on PSA levels and its impact on clinical decision-making for individual patients were evaluated based on different biopsy trigger cutoffs.

Results: ECLIA-PSA was measured in 74 participants both pre- and 37 ± 5 min post-DRE, mean age 57.2 ± 8.3 years, and mean prostate volume 33.6 (20-80) cm³. Both total and free ECLIA-PSA increased significantly after DRE (mean increase of 0.47 and 0.26 ng/ml, respectively, both p < 0.001). Different internationally accepted biopsy triggers were reached after DRE only: 5 total PSA > 3 ng/ml, 13 increase > 0.75 ng/ml, 3 PSA density > 0.15, and 1 free/total PSA < 0.18. On two occasions, patients were pushed away from biopsy trigger after DRE due to free/total PSA > 0.18. ICA-PSA was detectable (> 2.0 ng/ml) in 5 of 45 measured samples (11%) before DRE and 13/45 (29%) after DRE, p = 0.0316. Four among five detectable ICA-PSA tests increased after DRE.

Conclusion: Performing DRE immediately before PSA measurement might change the clinical decision-making on a significant number of occasions (roughly 1 in 3); even though the mean increase (0.47 ng/ml) looks deceivingly small. Further studies are required that include gold standard tests (biopsy, or imaging).

Keywords: Biopsy triggers; DRE; PSA; Prostate cancer; Screening.