Validation of Blood Spot Sampling for Gonadotropins and Ovarian Hormone Levels in Reproductive Age Women

Abstract

To determine whether blood spot sampling of gonadotropins[luteinizing hormone (LH), follicle stimulating hormone (FSH)] in ovulatory women produces results comparable to those obtained from plasma samples in order to validate the technique for use in reproductive research. Cross-sectional study One hundred women age 18-35 years old with a history of regular menstrual cycles and no recent use of hormonal contraception contributed both a blood spot sample from a finger-stick and a plasma sample through venipuncture during a single study visit during a random day within their menstrual cycles. Samples were evaluated for the presence of FSH and LH. All blood spot and plasma analyses were performed at a commercial laboratory (ZRT Laboratory, Beaverton, Oregon), with duplicate plasma samples assayed at Oregon HealthsScience University’s General Clinical Research Center (OHSU). Plasma samples were analyzed with commercially available enzyme immunoassays and these assays where then modified for blood spot analysis. Blood spot and plasma samples were assigned unique identifying numbers such that the analysis was blind to the relationship between the samples. A total of 100 women were enrolled with 86-paired samples available for analysis (1 screen failure with age >35, 1 unsuccessful venipuncture, 8 insufficient plasma samples, and 4 insufficient blood spot samples). The average subject was a 28 year old, Caucasian, nulliparous woman with a body mass index of 25 kg/m2. Significant positive correlations were found between the blood spot and plasma samples of FSH (0.91, p < 0.001) and LH (0.93, p < 0.001). Although the gonadotropin levels obtained from blood spots (mean FSH 4.0 mIU/mL, LH 5.4 mIU/mL) were significantly different from those derived from plasma samples (mean FSH 4.5 mIU/mL, p < 0.001; LH 6.2 mIU/mL, p < 0.001) the magnitude of these differences (mean difference FSH 0.5 mIU/mL, LH 0.8 mIU/mL) is not clinically relevant. Excluding imperfect blood spot samples (supersaturated, not sufficient quantity) did not greatly improve correlation. Gonadotropin levels obtained from blood spot samples correlate well with values obtained from standard plasma assays. Blood spot testing represents a less invasive technology than venipuncture that may improve the acceptability of daily measurement of reproductive hormone levels during reproductive research and/or clinical care. Based on these promising results, we are extending these studies to examine blood spot monitoring for ovarian hormones (estradiol and progesterone) and to track women through an entire menstrual cycle.