The Link Between Oxidative Stress and Male Infertility in Lithuania: A Retrospective Study

<i>Background and Objectives</i>: Male infertility is a growing public health concern, with up to 50% of cases lacking a clearly identifiable cause. This study aimed to assess the epidemiological characteristics of male infertility in Lithuania and evaluate the clinical utility of oxidative stress assessment using the MiOXSYS system. <i>Materials and Methods</i>: A two-stage retrospective study was conducted between 2019 and 2023 at one of the largest fertility centers in Lithuania. The first stage involved an epidemiological analysis of 718 men who met the inclusion criteria. In the second stage, 261 men underwent oxidation-reduction potential (ORP) testing using the MiOXSYS system. Semen parameters were evaluated according to World Health Organization (WHO) 2010 guidelines. ROC curve analysis was used to assess the diagnostic value of ORP. <i>Results</i>: Male infertility was identified as the sole factor in 20.1% of couples, while unexplained infertility accounted for 24.4% of all cases. Among normozoospermic men, 48.5% exhibited elevated ORP levels (>1.34 mV/10⁶ sperm/mL). ROC analysis demonstrated moderate diagnostic accuracy of ORP (AUC = 0.634; sensitivity: 75.3%; specificity: 51.5%). The inclusion of ORP testing reduced the proportion of unexplained cases and supported their reclassification under the Male Oxidative Stress Infertility (MOSI) framework. <i>Conclusions</i>: This study provides novel epidemiological data on male infertility in Lithuania and highlights the potential of ORP testing as a supplementary diagnostic tool. Systematic evaluation of oxidative stress may help better identify cases previously labeled as unexplained and enable more personalized treatment strategies.