Correlation between first morning sample and 24-hour urinary estriol excretion

The estriol concentration of a morning sample of urine from high-risk pregnant women was correlated with the total 24-hour estriol excretion. One hundred seventy sample pairs compared the estriol concentration of the morning specimen with those of a 24-hour specimen of the previous day, while 110 sample pairs compared the value of morning specimen with those of a 24-hour specimen of the following day. Although there is highly significant statistical correlation between those sample pairs, they are of modest magnitude. The mean values of the sample pairs are significantly different. Also, the morning sample estriol concentrations are significantly more variable than those of the 24-hour specimen.