Evaluation of an aqueous fluorometric continuous-flow method for measurement of total urinary estrogens

Measurement of urinary estrogen excretion is used extensively to monitor fetal welfare in utero, allowing the fetus at risk to be identified. We evaluated a direct all-aqueous fluorometric method adapted to a continous-flow (AutoAnalyzer I) system, using a spectrofluorophotometer for detection. In this method, which is based on a modified Kober reaction, NaBH4 is used to eliminate the known negative interference of glucose. The mean analytical recovery was 98%. Urines from 15 men showed no blank fluorescence. Comparison studies of the fluorometric method (x) and a manual method based on the Kober/Ittrich reaction (y) yielded the equation y = 1.53x + 4.38 (r = 0.9235). The incomplete correlation can be explained by erratic extraction in the manual Kober/Ittrich procedure (mean recoveries were 57%). A day-to-day precision (CV) of 5.2% can be achieved with the automated method. Samples are analyzed at a rate of 20 per hour, but this rate can be doubled, if necessary, without significant carryover problems. We conclude that the automated fluorometric method is accurate, precise, and inexpensive and therefore the method of choice for measuring urinary estrogens.