Within-person variability of the ratios of urinary 2-hydroxyestrone to 16 alpha-hydroxyestrone in Caucasian womens

The ratio of urinary 2-hydroxyestrone (2-OHE1) to 16 alpha-hydroxyestrone ( 16 alpha-OHE1) has been suggested as a potential biomarker for breast cance r risk. We evaluated within-person variability of this biomarker in ten hea lthy Caucasian women aged 23-58 years. Each study participant was asked to provide an overnight fasting morning urine sample once a week for an averag e of 8 weeks. These urine samples were assayed for 2-OHE1 and 16 alpha-OHE1 by using competitive enzyme immunoassay kits purchased from the ImmunaCare Corporation. The coefficients of variation for urinary 2-OHE1/16 alpha-OHE 1 over the study period ranged from 13.7 to 59.6% (mean, 33.3%) in our stud y participants. There was a good correlation between the level of the urina ry 2-OHE1/16 alpha-OHE1 ratio in any single urine sample and the average ra tio over the 8-week study period from the same woman, with the mean correla tion coefficient of 0.85. These results indicated that the within-person va riation of the 2-OHE1 to 16 alpha-OHE1 ratio for most women was moderate an d the level of this ratio in a single urine sample, in general, reflects re asonably well the level of this biomarker over a 2-month period. (C) 1999 E lsevier Science Inc. All rights reserved.