An Evaluation of Usefulness of Prostate Specific Antigen and Digital Rectal Examination in the Diagnosis of Prostate Cancer in an Unscreened Population: Experience in a Nigerian Teaching Hospital
Objective: To evaluate the usefulness of prostate specific antigen (PSA) and digital rectal examination (DRE) in the diagnosis of cancer of the prostate (CaP) amongst unscreened patients.
Patients, Materials ans Methods: A prospective study168 unscreened men who were referred for evaluation for CaP. They all had a 10-core extended transrectal prostatic needle biopsy using size 16 Tru Cut needle for either an elevated serum total PSA of >4ng/ml or abnormal DRE findings or both. Overall cancer detection rate was determined and detection rates were determined separately for patients with elevated PSA with normal DRE, abnormal DRE with normal PSA and those with both indications. The performances of each indication were determined separately and in combination in terms of their sensitivity, specificity, predictive values and accuracy. The results were compared amongst patients with different indications for biopsy.
Results: The overall cancer detection rate was 44.0%. Detection rates in patients with elevated PSA with normal DRE and abnormal DRE with normal PSA were 30.0% and 17.4% respectively. There was statistically significant increased detection of 61.2% amongst patients with both indications. The overall sensitivities of PSA, DRE and combination of both were 94.6%, 75.7% and 70.3% respectively while the specificities were 20.2%, 44.7% and 64.9% respectively. The accuracies of PSA, DRE and combination of both indications were 53%, 58% and 67.3% respectively while the PPVs were 48.3%, 51.9% and 61.2% respectively. Mean Gleason score was 6.82 while the overall complication rate was 23.2%
Conclusion: Neither PSA nor DRE is sensitive, specific, predictive or accurate enough on its own to be an ideal screening or diagnostic test for CaP. Therefore, optimal evaluation of patients with suspected CaP is best achieved with both even in unscreened populations.
Keywords: Prostate cancer, detection rate, sensitivity, specificity, predictive values, accuracy.