Effect of delays in processing blood samples on measured endogenous plasma sex hormone levels in women.

Time spent in transit may affect the concentration of various constituents of collected blood samples and, consequently, results of sex hormone assays. Whole blood was collected from 46 women, and one third was processed immediately, one third was stored at ambient conditions (22 degrees C) for 1 day, and one third was stored for 2 days. Estradiol concentration increased by 7.1% [95% confidence interval (95% CI), 3.2-11.3%] after a delay in processing of 1 day and by 5.6% (95% CI, 0.2-11.4%) after a delay in processing of 2 days; the change was most apparent at lower than median concentrations. Progesterone concentrations showed no substantial change. Testosterone concentrations changed by 23.9% (95% CI, 17.8-30.3%) after a delay of 1 day but little thereafter. The sex hormone-binding globulin concentration decreased by 6.6% (95% CI, 4.6-8.6%) and 10.9% (95% CI, 8.1-13.6%), follicle-stimulating hormone increased by 7.4% (95% CI, 4.2-10.7%) and 13.9% (95% CI, 8.7-19.3%), and luteinizing hormone increased by 4.9% (95% CI, 1.3-8.5%) and 6.7% (95% CI, 2.2-11.5%) after a delay in processing of 1 and 2 days. Increases in calculated values for biologically available levels of estradiol and testosterone were greater than the increases seen in measured total hormone concentrations. Similar changes are likely when samples are delayed in transit, and evidence of etiology may be obscured unless study designs or analyses take into account processing delays.