An interlaboratory study of an automated technique for the assay of urinary oestrogens

Oestrogen determinations in urine from pregnant women: a review of six years' quality assessment in the United Kingdom

Since 1974 laboratory performance in the estimation of oestrogens in urine from pregnant women has been assessed in about 150 laboratories by analysis, at intervals of three weeks, of samples of freeze-dried urine. An index of discrimination, delta (= 2.7 SD derived from results reported on six pairs of duplicates), was calculated for each participant laboratory to provide a measure of between-batch precision. There has been a gradual improvement in laboratory performance assessed in this way. Initially, only 45% of the participants were able to discriminate between two 24-hour urine samples, differing in oestrogen by at least 20 mumol, when analyses were performed on different days. In the final period ending March 1980, 61% of participants achieved this standard.

Comparison of total urinary oestrogens and total serum oestriol in pregnancy

The total oestrogens detected by fluorescence in 24-h urine and the concentration of total oestriol detected in serum by radioimmunoassay were estimated in 51 women during the second half of pregnancy. The statistical analysis showed a linear regression between urinary excretion and serum concentration according to the equation y = -2.89 + 2.82x (y = serum oestriol). The correlation coefficient over all pairs of estimations (N =567) was r = 0.69, which is very highly significant (P less than 0.0001). The analysis of the individual pregnancies showed that the linear correlation coefficient was significant (P less than 0.05) in 35 cases, poorly significant (0.05 less than P less than 0.1) in 3 cases and not significant (P less than 0.1) in 5 cases. The correlation could not be calculated in 8 cases because the number of estimations was too small. These values were compared empirically (normal/pathological). There was agreement in 6 cases and no agreement in 2 cases. The results show on the one hand that the radioimmunological estimation of total oestriol in serum can be used in the same way as urinary excretion of oestrogens for monitoring the feto-placental unit. On the other hand, the study confirms that a "simple" fluorimetric Kober-Ittrich method can give at least the same clinical information as a radioimmunoassay of relatively high cost. It may be concluded indirectly from the results that a considerable diurnal rhythm or substantial day-to-day fluctuation in the production of oestriol are unlikely.

Some ionic and dilution effects in the measurement of urinary oestrogens in pregnancy

The estimation of oestrogen in aqueous solutions and pregnancy urines using an automated procedure is affected by the presence of certain ions, and by dilution. These effects have been studied by calculating regression equations from the values obtained with urines to which ions have been added with and without urine dilution. The results suggest that the ionic effect is chemical rather than physical and that there is no advantage in including a predilution step in the analysis. Other means of removing the ionic effects have so far proved unsuccessful.

Comparison of an all-aqueous automated urine pregnancy oestrogen method with one using organic solvent extraction

A comparative study between an all-aqueous automated urine pregnancy oestrogen method and a well established one requiring organic solvent extraction showed good agreement (r = 0.992). Advantages offered by the all-aqueous method include a faster rate of sample analysis and elimination of the difficulties of phase separation. The storage of urine for 5 days did not affect the oestrogen concentration measured by the all-aqueous method. Glucose, which reduced the apparent oestrogen concentration, was readily removed by treatment of the urine with borohydride, and treated urines showed good recoveries. The recovery of oestrogen was inadequate when glucose was removed from urine by incubation with yeast, possibly due to the formation of acetaldehyde.

Validation of methods for determination of urinary estriol during pregnancy using mass fragmentography

A specific and accurate method for determination of urinary estriol during pregnancy is described. After acid hydrolysis of 1 ml urine, a fixed amount of [2,4-2H2] estriol (usually 15 mug) is added and the mixture is extracted with diethyl ether. The extracted estriol is converted into the tri-trimethylsily derivative and the amount of unlabeled estriol is determined from the ratio between the recordings at m/e 504 and m/e 506 obtained after analysis with a gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions used correspond to the molecular peak in the mass spectrum of unlabeled and (2,4-2H2)-labeled tri-trimethylsilyl derivative, respectively. The relative standard deviation of the method was about 6%. The method was compared with a photometric method using the Kober reaction and the gas liquid chromatographic method used in routine analysis. There was a good correlation in both cases and the regression coefficient was 1.5 and 1.3, respectively.

Urinary total oestrogen values determined by an automated method in normal and abnormal pregnancies

Urinary total oestrogen values in late pregnancy have been determined by an automated, fluorimetric method based on the Kober reaction and Ittrich extraction. The normal range was obtained from 360 samples from 56 patients. The mean value at 40 weeks gestation was 52.6 mg/24 h and the 95 per cent probability bounds were 29.1 and 95.3 mg/24 h, obtained after initial calculations on logarithm values. "Small for dates" foetuses in good condition at birth were associated with oestrogen values generally below the normal mean. They were usually well discriminated from foetuses that died in the uterus. These were always associated with oestrogen values below or approaching 10 mg/24 h before death except when growth had been normal and death was due to mechanical complications at delivery.