Study of Interlaboratory Reliability and Reproducibility of Estrogen and Progesterone Receptor Assays in Europe: Documentation of Poor Reliability and Identification of Insufficient Microwave Antigen Retrieval Time as a Major Contributory Element of Unreliable Assays

Anthony Rhodes, Bharat Jasani, Andre J. Balaton, Diana M. Barnes, Elizabeth Anderson, Lynda G. Bobrow, Keith D. Miller

Research output: Contribution to journalArticle

139 Citations (Scopus)


Immunohistochemical assays for estrogen receptors (ERs) and progesterone receptors (PRs) have not been surveyed for technical validity. In the present study, the reliability of the immunohistochemical assay for ER and PR was evaluated using data from 105 laboratories participating in external quality assessment (EQA) during a 2-year period. Technical variables associated with reliable immunostaining were analyzed. The efficiency of the antigen retrieval step was identified as the single most important contributory factor influencing the overall reproducibility of the assays. Reliable assays were found in 24 (36%) of 66 laboratories participating in continual EQA, including the majority of centers known to have clinically validated results. Inadequate assay sensitivity, with subsequent weak staining, was the main cause of poor and variable results by laboratories using microwave antigen retrieval: too short a heating time was identified as the principal contributory factor. Extension of the heating time resulted in significant improvement regardless of all other variables in the immunohistochemical protocol. Continual participation in EQA is an effective means for identifying and ameliorating variables that influence the reliability of immunohistochemical assays for predictive markers, thereby assisting in technical validation and standardization.

Original languageEnglish
Pages (from-to)44-58
Number of pages15
JournalAmerican Journal of Clinical Pathology
Issue number1
Publication statusPublished - Jan 1 2001



  • Estrogen receptors
  • Immunohistochemistry
  • Microwave antigen retrieval
  • Progesterone receptors
  • Technical validation

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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