Establishing reference intervals for hCG in postmenopausal women

Background Plasma concentrations of human chorionic gonadotropin (hCG) have been shown to increase with age due to pituitary secretion. We previously recommended that an hCG cutoff of 14.0 IU/L be used for women ≥ 55 years of age. However, it remains unknown whether concentrations > 14.0 IU/L can be expected in women with advanced age. Our objectives were to establish plasma hCG reference intervals and correlate follicle stimulating hormone (FSH) and hCG concentrations in postmenopausal females ≥ 55 years. Methods Residual plasma samples from 798 women ≥ 55 years were utilized with 303, 269, and 226 samples belonging to the age groups 55–69, 70–84, and ≥ 85 years, respectively. FSH and hCG were measured using the Abbott ARCHITECT. All positive hCG samples (hCG ≥ 5 IU/L) were analyzed for potential heterophile antibody interference and 3 were excluded. Electronic medical records were reviewed and patients with malignancy were excluded. Results 8% (56/666) of women age ≥ 55 years had plasma hCG ≥ 5 IU/L. There were 19, 16, and 21 patients with hCG ≥ 5 IU/L in the age groups 55–69, 70–84, and ≥ 85 years, respectively. The highest hCG concentrations observed in each age group were: 55–69 years maximum = 11.7 IU/L and 97.5th percentile = 9.6 IU/L; 70–84 years maximum = 18.09 IU/L, 97.5th percentile = 6.2 IU/L; ≥ 85 years maximum = 11.1 IU/L and 97.5th percentile = 10.0 IU/L, and the overall 97.5th percentile = 8.5 IU/L for all women ≥ 55 years of age. Neither hCG nor FSH concentrations continued to increase with age in women ≥ 55 years. Conclusions The prevalence of positive hCG in women ≥ 55 years is 8%. This study confirms our previously recommended cutoff of 14 IU/L for women ≥ 55 years of age. In women ≥ 55 years of age, FSH concentrations do not predict hCG concentrations.