European Journal of Nuclear Medicine

, Volume 17, Issue 3–4, pp 111–115 | Cite as

Analytical and clinical evaluation of a new one-step non-analogue radioimmunoassay for serum-free thyroxine

  • Rémy Sapin
  • Françoise Gasser
  • Jean-Louis Schlienger
  • Jacques Chambron
Original articles

Abstract

We evaluated analytically and clinically the new one-step non-analogue free thyroxine (FT4) assay (Amerlex-MAB from Amersham), using a labelled monoclonal thyroxine-specific antibody as tracer, in comparison with the Gammacoat two-step FT4 kit (Baxter). Analytical performances of the new kit were excellent: within and between run coefficients of variation were < 5% in the working range. Clinical sensitivities for hypo- and hyperthyroidism were comparable for both kits (FT4 Amerlex-MAB 95% confidence interval: 12–25 pM). When serum was supplemented with albumin we observed a slight decrease in FT4 values measured by both kits. When oleate was added to serum we noted a moderate increase with the Amerlex-MAB kit up to 10 mM oleate added and a much more marked increase with the two-step kit. Results obtained with patients from particular euthyroid populations, known to have low albumin or high free fatty acids concentrations or to have perturbed FT4 results when measured by an analogue-based method, agreed with those of the in vitro studies. With these patients the specificity of the Amerlex-MAB FT4 results was good but slightly decreased compared with the two-step FT4 method, except for heparin-treated patients who were all classified according to their euthyroidal status (17/17 instead of 13/17 with the two-step kit).

Key words

Free thyroxine Non-analogue radioimmunoassay Effect of albumin Effect of oleic acid Thyroid status 

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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Rémy Sapin
    • 1
  • Françoise Gasser
    • 1
  • Jean-Louis Schlienger
    • 2
  • Jacques Chambron
    • 1
  1. 1.Institut de Physique BiologiqueFaculté de MédecineStrasbourg CédexFrance
  2. 2. Service de Médecine InterneHôpital de FlautepierreStrasbourg CédexFrance

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