Oestradiol Assay Interference from Fulvestrant

The MHRA and Roche diagnostics (Manufacturer of the Oestradiol assay used by TDL) have notified that interference from the drug Fulvestrant (Faslodex®) may cause falsely elevated Oestradiol results. Tests have demonstrated that with a Cmax concentration of Fulvestrant of 92.1 nmol/L, the measurement of Oestradiol was approximately 300% falsely elevated ( i.e. a neat sample that provided an oestradiol measurement of 107 pmol/L yielded a result of 315 pmol/L).  Assessment of the oestrogen status from this Oestradiol assay of a woman being treated with this drug would therefore give misleading results.


For any patients on treatment with Fulvestrant for whom accurate measurement of Oestradiol is required, TDL would refer the sample to a Reference Laboratory for a mass spectrometry based assay known not to be subject to this interference.


For further information please contact Annette Wilkinson, Director of Business Development and Service ( annette.wilkinson@tdlpathology.com )


June 2016