Citrate concentrations in human seminal fluid and expressed prostatic fluid determined via 1H nuclear magnetic resonance spectroscopy outperform prostate specific antigen in prostate cancer detection

Purpose: We compared the performance of citrate concentration measurements in unprocessed human semen and expressed prostatic secretions from controls and from patients with biopsy confirmed prostate cancer to that of prostate specific antigen testing with respect to specificity and sensitivity for prostate cancer detection. Materials and Methods: Semen and expressed prostatic secretions were collected in biopsy proven, prostate cancer bearing and noncancer bearing cases. Citrate concentrations were determined by quantitative in vitro, high field, water suppressed proton nuclear magnetic resonance spectroscopy. Assessments of the diagnostic performance of citrate and prostate specific antigen results in our study populations were made by ROC curve analysis. Results: Citrate was measured in samples from 61 participants, of whom 16 without and 21 with cancer donated semen, and 17 without and 7 with cancer donated expressed prostatic secretions. Mean citrate +/- SE compared to that in controls was 2.7-fold lower in patients with cancer samples in semen (132.2 +/- 30.1 vs 48.0 +/- 7.9 mM, p < 0.05) and expressed prostatic secretions (221.4 +/- 55.4 vs 81.5 +/- 36.0 mM, p < 0.05). ROC curve analysis showed that measurements of citrate in semen performed as well as measurements of citrate in expressed prostatic secretion for detecting prostate cancer (AUC 0.81, 95% CI 0.60 to 0.92 and AUC 0.73, 95% CI 0.38 to 0.90, respectively, p > 0.05). ROC curve analysis also showed that the measurement of citrate in either fluid outperformed prostate specific antigen measurement for detecting prostate cancer in these subjects (AUC 0.61, 95% CI 0.44 to 0.74). Conclusions: In vitro nuclear magnetic resonance spectroscopic measurement of the citrate concentration in semen or expressed prostatic secretions outperforms prostate specific antigen testing for detecting prostate cancer.