Diagnostic considerations in the measurement of human chorionic gonadotropin in aging women.

BACKGROUND: Human chorionic gondadotropin (hCG) screening tests are performed on nearly all female patients of childbearing age before any medical intervention. Although older women usually have negative hCG test results, positive results do occur and may cause clinical confusion. We examined changes with age in serum hCG concentrations in nonpregnant women and investigated the use of serum follicle-stimulating hormone (FSH) measurements as an aid to interpreting higher than expected ("positive") hCG results.

METHODS: We used 240 serum specimens for each of 4 female cohorts: pregnant, > or =18 years; nonpregnant, 18-40 years (premenopausal); nonpregnant, 41-55 years (perimenopausal); and nonpregnant, >55 years (postmenopausal). Patients were excluded if they had an ectopic pregnancy, a history of trophoblastic disease or a germ-cell tumor, or if no chart was available for review. Quantitative hCG and FSH tests were performed on each specimen.

RESULTS: Serum hCG concentrations in nonpregnant women increased with the age of the women. hCG results were higher and significantly different (P < 0.0001) for nonpregnant women >55 years (<2.0 to 13.1 IU/L) compared with nonpregnant women 18-40 years (<2.0 to 4.6 IU/L) and 41-55 years (<2.0 to 7.7 IU/L). Nineteen nonpregnant women >40 years of age had hCG concentrations > or = 5.0 IU/L, all with an FSH concentration >32.4 IU/L. The highest FSH concentration in pregnancy was 7.3 IU/L.

CONCLUSIONS: Serum hCG increases with age in nonpregnant women. A cutoff of 14.0 IU/L should be used when interpreting hCG results in women >55 years of age. Pregnancy is unlikely in perimenopausal women 41-55 years of age with an hCG between 5.0 and 14.0 IU/L if serum FSH is >20.0 IU/L.