Sensitivity and Specificity of Digital Rectal Examination for the Diagnosis of Prostate Cancer at the Kano Teaching Hospital - A Comparative Analysis

Abstract

Background: Prostate cancer (CaP) is the most common non-cutaneous cancer among males and the fourth most common cause of cancer in males globally. Unfortunately, Sub-Saharan Africa lacks the relevant resources and organized screening program that has led to the late presentations in the region. Digital rectal examination (DRE) is a test commonly used to screen for prostate carcinoma and is by far the oldest and cheapest modality available for screening.

Objective: We hypothesized that digital rectal examination has a correlation to the diagnosis of prostate cancer. This study was meant to evaluate the sensitivity and specificity of DRE in the diagnosis of prostate cancer and compare the outcome to published data.

Methodology: This is a prospective study conducted at the Aminu Kano Teaching Hospital involving 87 symptomatic patients who were screened for prostate cancer (2014). Patient with DRE suspicious of malignancy i.e. (nodular, hard, asymmetrical prostate) or PSA >4ng/ml despite the prostate consistency were included in the study. The digital rectal exams were performed in a lateral decubital position to assess the prostate consistency and underwent transrectal ultrasound guided sextant biopsy for histological diagnosis.

Results: There was a total of 87 participants that underwent DRE in the study with age range from 50 – 96 years. Univariate analysis showed a mean age of 68.1 years with standard deviation of (SD +9.4). The detection rate of prostate cancer was 28.7%. Bivariate analysis of DRE to diagnosis of prostate cancer showed a sensitivity of 68.0% and specificity of 83.9%. The positive predictive value and the negative predictive value were 63.0% and 86.7% respectively. The study showed some evidence of a relationship between DRE and the diagnosis of prostate cancer with a (Pearson Chi Square Test=23.4, df=1,) with a statistical significance (p=<0.001).

Conclusion: PSA and Digital rectal exam combined have a higher sensitivity in the diagnosis of prostate cancer. However, DRE alone has a lower sensitivity but a much higher specificity in the diagnosis of CaP. DRE still has a role in the diagnosis of CaP because it is minimally invasive, cheaper and can detect some prostate cancers that are missed by PSA screening.