The Predictive Value of Prostate Specific Antigen Density, Percentage Free Prostate Specific Antigen and the Combination for Prostate Cancer Detection in Grey Zone

<i>Introduction:</i> Prostate cancer is a common malignancy affecting men beyond the middle age. In advanced countries, the life time risk of developing microscopic prostate cancer in men is 30%. However, it is slow-growing and the risk of developing clinical disease is 16%, while the lifetime risk is 3%. It is not common in those below 50 years, but after this age there is a steady increase in its incidence. The objective of this study was to determine the predictive value of prostate specific antigen density (PSAD), percentage free Prostate specific antigen and the combination (PSAD+%FPSA) for cancer detection in the grey zone at a tertiary health center in north central Nigeria. <i>Methodology:</i> A prospective study which was carried out over one year and three months. Each subject had a clinical evaluation involving relevant history, physical examination with digital rectal examination of the prostate gland, followed by blood sampling for both total and free PSA. These samples for PSA were sent to the chemical pathology laboratory. The percentage free PSA was calculated by finding the ratio between free PSA and total PSA and multiplying the result by 100. Also, a transabdominal ultrasound scan was done to determine the prostate volume. The PSA density was calculated by dividing the PSA by the total prostate volume. All patients had digitally guided transrectal prostate biopsy. The analysis were in 3 subsets; PSAD, %FPSA and the combination (PSAD+%FPSA). Results were analysed using SPSS version 20. P value <0.05 was considered significant. Charts and tables were used to express the data. The receiver operating characteristic curve (ROC) was used to determine the predictive power of PSAD and %FPSA, the combination (PSAD+%FPSA) in prostate cancer detection and hence the more predictive of them all. <i>Results: </i>Forty two men with mean age of 67.93 ± 7.11years who had PSA in the grey zone were recruited. Only 5(12%) had diagnosis of prostate adenocarcinoma. Mean age of those with adenocarcinoma was 69.40 ± 1.67years. There was no statistically significant correlation between prostate adenocarcinoma and the variables; PSAD, %FPSA and the combination (PSAD+%FPSA), with P values of 0.517, 0.453 and 0.451 respectively. However when the ROC curve was drawn, the AUC was highest for PSAD at 0.524 with a cut-off value of 0.108ng/ml<sup>2</sup>. While the AUC and cut-off was 0.373, 29.40 and 0.373, 30.50 for %FPSA and the combination (PSAD+%FPSA) respectively. Additionally, using a two-by-two table, the positive predictive value for adenocarcinoma was 21.1% for PSAD, compared to 11.9% for %FPSA and 7.1% for the combination.<i> Conclusion:</i> The study showed that PSAD was the most predictive of the 3 parameters. A PSAD cut-off value of 0.108 (sensitivity of 80% and specificity of 20%) is suggestive of prostate adenocarcinoma in patients with PSA in the grey zone.