Relationship Between Free/Total Prostate-Specific Antigen And Prostate Volume In Patients With Biopsy Proven Benign Prostatic Hyperplasia

IntroductionBenign prostate hyperplasia(BPH),one of the most common diseases in elderly men,can cause bothersome lower urinary tract symptoms(LUTS) that affect quality of life by interfering with normal daily activities and sleep patterns.It has been suggested that prostate volume is a significant predictive factor for progression of BPH(eg,acute urinary retention and need for BPH-related surgery) and response for pharmacotherapy. TRUS is considered to be the most accurate method for PV assessment.However,it is not feasible to perform TRUS as a routine test for its invasiveness and limited availability.PSA is a glycoprotein which is produced by the epithelial cell of prostate tissue.The measurement of serum prostate-specific antigen is used for screening and early detection of prostate cancer.It has been shown that serum PSA correlates well with PV and elevated PSA levels are also suggested to predict BPH progression. Nevertheless,most of the data on the relationship between PSA and PV have been based upon western populations.Recent reports that investigated into Asian men revealed that the PSA-PV relationship seemed to be not the same across different races.The exact relationship between serum PSA levels and PV has not yet been established in Chinese men.The objective of this study is to analyze the relationships among serum PSA,free PSA,prostate volume and patients' age in Chinese men with histologically proven BPH, and stress the implication of the fPSA as a proxy marker to estimate PV.Materials and methodsFrom 2003 to 2008,a total of 268 patients with a PSA less than 10 ng/ml and biopsy proven benign prostatic hyperplasia were enrolled in this study.Prostate volume was measured with transrectal ultrasonography,tPSA and fPSA were determined using the EIA method.Patients with a history of prostate surgery,prostate cancer and conditions other than BPH were excluded.The relationships among age,PV,tPSA and fPSA were analyzed with the Pearson correlation coefficient(r).A linear regression model was used to determine the relationship between prostate specific antigen and prostate volume.The relationship between PV and fPSA was further analyzed by age-stratified and PSA-stratified cohorts.Receiver-operating characteristic(ROC) curves were constructed to evaluate and compare the ability of serum tPSA and fPSA to estimate thresholds of PV in men with biopsy-proven BPH.ResultsAge did not significantly correlate with tPSA.Among relationships between tPSA, fPSA,age and PV,The highest degree of correlation was found between fPSA and PV (r=0.456,p＜0.001),while the correlation coefficient was much lower between tPSA and PV(r=0.278,p＜0.001).The ROC curves revealed that the performance of fPSA in predicting threshold prostate sizes(30,40,and 50 ml) showed areas under the curve (AUC) ranging from 0.72 to 0.75,denoting better discrimination of PV than tPSA,of which the AUCs ranged from 0.56 to 0.62.ConclusionAlthough tPSA significantly correlated with PV in Chinese men with biopsy-proven BPH,the correlation between fPSA and PV was much stronger,and fPSA performed significantly better than tPSA at predicting thresholds of PV.fPSA may be used to estimate PV and could be a useful tool in making therapeutic decisions in Chinese men with BPH.