Purpose: This study was undertaken in order to establish a new reference value for the total antioxidant capacity (TAC) in seminal plasma as a predictor of fertility. This study also aims to propose a detailed protocol for the TAC assay including calculation of assay results and assessment of sensitivity and specificity over possible cutoff values in infertile men and controls with proven and unproven fertility.
Methods: Seminal plasma from 279 infertile patients and 46 normal healthy men referred to a male infertility testing laboratory were tested to measure TAC by a colorimetric assay kit. Receiver operating characteristics (ROC) curves were generated to establish cutoff values, sensitivity, and specificity, and the distribution of cutoff values in controls and infertile patients was calculated.
Results: Infertile patients showed significantly lower levels (mean ± SEM) of total antioxidants (micromolar Trolox equivalents) in their seminal plasma (1863.84 ± 27.16 μM) compared to those from fertile men (2013 ± 56.04 μM, P = 0.019). A preferred cutoff TAC value of 1947 μM could facilitate better diagnosis of oxidative stress (OS) in men with male factor infertility. At this threshold, the specificity of TAC assay was 63.0 % and the sensitivity 59.5 % with a positive predictive value of 90.7 % and a negative predictive value of 20.4 %.
Conclusions: Our results establish a new diagnostic cutoff TAC value of 1947 μM in seminal plasma to distinguish prevalence of OS in infertile patients compared to healthy men. This study provides a robust reference value of seminal plasma TAC that may provide an important diagnostic tool to the physicians for managing OS and male factor infertility in such patients.
Keywords: Diagnostic value; Male infertility; Oxidative stress; Seminal plasma; Specificity and sensitivity; Total antioxidant capacity.