Measurement of gonadal hormones in dried blood spots versus serum: Verification of menstrual cycle phase

In the present study, we show that blood spot assays for estradiol, progest erone, and testosterone are a reliable, accurate, and sensitive means for m easuring circulating gonadal hormones. The lower limit of sensitivity of ea ch blood spot assay is sufficient to determine gonadal hormone levels in ad ult females. Correspondence of serum to blood spot measures is high, with b lood spot hormone levels explaining an average of 88.60% of the variance in serum gonadal hormones in females, but only 46.20% in males. We provide fo rmulas for converting hormone levels in blood to hormone levels in serum (w hich traditional endocrinology studies report). Finally, we show that caref ul attempts to estimate hormone status by day-count methods are unreliable when compared to hormone assay in blood spots, (C) 2001 Academic Press.