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Measurement of serum estradiol (E2) and progesterone (PRG) allows monitoring of follicular growth and prediction of the day of ovulation in natural cycles. In combination with vaginal ultrasonography, serum E2 and PRG are used for the monitoring of ovarian superovulation for assisted reproduction. We carried out a clinical evaluation of the VIDAS E2 and PRG assays on a fully automated random access analyzer (miniVIDAS, bioMérieux) by retrospective analysis of frozen serum samples obtained from 16 natural cycles monitored for frozen embryo transfer (FRET) and in superovulation cycles. The superovulation cycles consisted of 28 long gonadotropin-releasing hormone (GnRH) agonist protocol cycles and 15 GnRH antagonist protocol cycles. In FRET cycles we found a good correlation between serum E2 and the diameter of the dominant follicle measured by ovarian ultrasonography. Serum E2 values measured throughout the cycles and follicular phase PRG values were representative of normo-ovulatory cycles. In GnRH agonist long protocols, we found serum E2 and PRG values compatible with castration levels induced by pituitary desensitization. During gonadotropin treatment a close, highly significant correlation was observed between serum E2 and ultrasonographic follicle measurements with both GnRH analogue protocols. Serum PRG measured for 5 days prior to human chorionic gonadotropin (hCG) administration in the agonist cycles was compatible with the absence of premature luteinization. In conclusion, VIDAS E2 and PRG assays are precise and sensitivetoolsforevaluating natural cycles (based on the results in FRET cycles) and for monitoring ovarian superovulation.

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SUMMARY. The analytical and clinical performance of three radioisotopic methods for the measurement of free thyroxine-c-GammeCoat" (1 25 1) Free T 4 , RIA-gnost® FT 4 and Amerlex-MAB* FT 4-were assessed in comparison with the Sclavo twostep chromatographic method. The analytical evaluation indicated excellent performance of Amerlex-MAB FT 4 . For the other methods, precision and sensitivity were comparable and acceptable for routine use. Only GammaCoat FT 4 showed a significant positive intra-assay drift. None of the methods showed a significant correlation with thyroxine-binding globulin. Amerlex-MAB FT 4 results were weakly positively correlated with albumin. Sclavo, RIA-gnost and particularly GammaCoat FT 4 results were affected by the presence of increased concentrations of free fatty acids. All methods classified hyperthyroid patients correctly. Slight overlaps existed between the hypothyroid and euthyroid populations. Significant decreases in free thyroxine (FT 4 ) during the third trimester of pregnancy were detected by all assays. In patients with chronic renal failure, serum FT 4 was within reference limits more often when measured by Sclavo or Amerlex-MAB methods than by RIA-gnost or GammaCoat techniques. In conclusion, all assays performed well from both technical and diagnostic points of view. Additional key phrases: imprecision; effect of thyroxine-binding globulin, albumin and free fatty acids; reference interval; diagnostic efficiencyThyroid hormones circulate in the blood in free and bound forms, which are in equilibrium with one another. Thyroid hormones bind to thyroxine-binding globulin (TBG), thyroxine-binding prealbumin and albumin. Approximately 0·03% of thyroxine (T 4 ) is present in its free form and only this fraction is metabolically active. 1.2 Therefore, an exact assessment of the metabolic status requires determination of the biologically active free thyroid hormone.Several simple, fast and economical commercial free thyroxine (FT 4 ) kits have been developed. Our aim here was to evaluate three of these FT 4 assays, GammaCoat" (1 25 1) Free T 4 (GFT 4 ) , RIA-gnost® FT 4 (RFT 4 ) and Arnerlex-MAB*FT 4 (AFT 4 ) , in comparison with the twostep chromatographic method of Sclavo (SFT 4 ) , which we currently use and which is a reliable but expensive and labour intensive technique.Correspondence: M Van Blerk MD.We compared these assays for precision, reference values in euthyroid adults and pregnant women, influence of binding proteins, performance in thyroid disease and severe illness and practicability in a routine hormone laboratory. MATERIALS AND METHODSFree thyroxine assays Sclavo SFT 4 was based on a chromatographic separation on Sephadex LH-20 columns followed by a radioimmunoassay (RIA) on Liso-Phase columns. Five hundred microlitres of sample was added into LH-20 columns containing Sephadex LH-20 gel and about 0'5mL 0'2mol/L Tris buffer, pH 7-4. The samples were allowed to pass through the Sephadex gel during 15min. Protein fractions were then eliminated by washing the columns w...