A comparison of blood spot vs. plasma analysis of gonadotropin and ovarian steroid hormone levels in reproductive-age women

Objective: To compare LH, FSH, P, and E₂ levels obtained from blood spot vs. plasma (single-visit study) and to determine whether blood spots can document circulating hormone levels during ovulatory cycles (menstrual-cycle study). Design: Cross-sectional study. Setting: Academic center. Patient(s): Women 18-35 years of age with regular menstrual cycles and no recent use of hormonal contraception. Intervention(s): Women contributed both a blood spot sample from a finger-stick and a plasma sample through venipuncture on a random day within their menstrual cycle (n = 100, single study visit). Five additional women were followed for an entire menstrual cycle with biweekly venipuncture and daily self-collected blood spot sampling. Samples were analyzed for FSH, LH, P, and E₂. Main Outcome Measure(s): Correlation between blood spot and plasma levels. Result(s): Significant positive correlations were found between the blood spot and plasma samples in the single-visit study (r²: FSH, 0.91; LH, 0.93; P, 0.83; and E_2, 0.70). Two of the 5 menstrual-cycle study women had ovulatory cycles based on P levels (>3 ng/mL) and an LH surge. Daily blood spot sampling was better able to document hormonal changes than biweekly venipuncture. Conclusion(s): Blood spot monitoring of FSH, LH, P, and, to a lesser extent, E₂, appears to be as valid as traditional plasma assays for clinical research and care.