Reference values of human epididymis protein 4 in the Bulgarian population – assessment of the influence of age, menopause, pregnancy, and renal function

Introduction : Human epididymis protein 4 (HE4) is increasingly utilized in diagnosing pelvic masses and monitoring patients with ovarian or endometrial carcinoma. However, various publications and diagnostic kit manufacturers report a wide range of reference and threshold values, complicating accurate clinical interpretation and reducing the marker’s clinical utility. This study aimed to establish reference values for HE4 in the Bulgarian female population and investigate the impact of physiological factors such as age, menopause, and pregnancy, as well as pathological conditions like impaired renal function, on marker levels. Materials and methods : The study included 338 women: 246 healthy, nonpregnant women aged 20–82 (124 of whom were premenopausal); 52 pregnant women; and 40 women with reduced renal function, as determined by serum creatinine levels. Data were collected on gynecological status, renal and hepatic function, diabetes, and other clinically significant chronic or oncological diseases. Serum HE4 concentrations were measured using an indirect chemiluminescent microparticle immunoassay (CMIA) on the Architect ci8200 system (Abbott Diagnostics). Statistical analyses were performed using SPSS version 25.0, and values were considered statistically significant at p <0.05. Results : The upper reference limit for HE4 in healthy women (95th percentile with 95% confidence interval) was 62.43 (59.02–65.45) pmol/L. For menopausal status, upper reference limits were 53.22 (50.80–60.82) pmol/L for premenopausal women and 65.31 (61.57–68.35) pmol/L for postmenopausal women. In pregnant women, the upper HE4 limit was 50.90 pmol/L, with values by gestational age of 57.73 pmol/L (first trimester) and 46.35 pmol/L (second trimester). None of the women with serum creatinine within the reference range had elevated HE4 levels, whereas all patients with elevated creatinine had HE4 levels above the 95th percentile for their respective age and menopausal status. Conclusions : The established reference limits for HE4 in this study significantly differ from those proposed by Abbott Diagnostics that are used to date. Implementing these limits in clinical practice could enhance the marker’s sensitivity and enable earlier detection of gynecological malignancies. The data confirm that HE4 levels depend on age, particularly after 60 years, and on reduced renal function, necessitating cautious interpretation in these patients. No significant differences in HE4 concentrations were observed between pregnant and non-pregnant women, supporting the use of uniform reference values regardless of pregnancy or gestational stage.