An ‘In-House’ Method for the Assay of Serum Total Oestriol in Pregnancy Using 125 I Label

Commercial RIA kits for the assay of serum total oestriol using ¹²⁵I label are used widely in monitoring fetal well-being in pregnancy; they are, however, very expensive for large-scale routine use. An ‘in-house’ assay using commercially available [¹²⁵I]oestriol label and antiserum produced by the S.E. and S.W. Thames Regional Antibody Production Unit has been developed. Technical aspects of the method are described. The assay is compared with two commercial kits and correlates very well with one of them. The assay gives good precision and can be used with substantial savings in cost.