The diagnostic utility of the PSA screening test in a Ghanaian population

An immunoradiometric (IRMA) protocol was used in the PSA test to measure PSA levels in the sera of 240 men presenting with various complaints bordering on their prostate condition. These men were also made to undergo a fine-needle biopsy. Using the universal cut-off of 4.0ng/ml and the histopathological findings from the biopsies as a 'gold standard' statistical performance criteria (such as Sensitivity, Specificity, False Positive Ratio (FP), False Negative Ratio (FN), Likelihood Ratio (L), Positive Predictive Value (PPV), Negative Predictive Value (NPV), Prior Odds Ratio (Ω and Prevalence) were determined and compared with available literature values. This was to determine the diagnostic efficiency and utility of the PSA test for our Ghanaian population of 240 men. The test returned a Sensitivity and Specificity of 92.9% and 18.6% respectively. The FP and FN ratios were 81.4% and 7.1% respectively. The PPV and NPV were 38.1% and 82.9% respectively while the Prior Odds and Prevalence were 7:13 and 35% respectively. High sensitivities ranging from 79-90% and as low as 34 % have been reported. On the other hand specificities ranging from 59% to 70% have also been reported. The PPV compares favourably with the available literature values to us: within range 28-40%. The PPV and NPV values together with an application of Baye's theorem indicates that in our setting the PSA test is more efficient in ruling out disease than in detecting it. (au)