Unconjugated estriol in serum as measured by liquid chromatography with electrochemical detection, compared with radioimmunoassay.

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Abstract
Concentrations of unconjugated estriol in maternal serum or plasma increase throughout pregnancy, particularly during the third trimester. We present and discuss the results of a comparative study of unconjugated estriol as measured by a new "high-performance" liquid-chromatographic assay and by a conventional semiautomated radioimmunoassay procedure. In the new method, serum is extracted and chromatographed on a reversed-phase mu Bondapak-C8 column under radial compression. The estriol peak is detected with a glassy-carbon electrochemical detector. The chromatographic results (y) correlated well with the RIA results (x) for 105 samples from 45 pregnant women in their third trimester (y = 1.07x - 0.55 micrograms/L, r = 0.933), with no significant difference between the means of the two methods.