Precision and method bias of two assays for oestradiol: consequences for decisions in assisted reproduction

Oestradiol monitoring in assisted reproduction is empirical, with no proof of benefit. Precise oestradiol estimation will be an essential pre-requisit e for high quality evaluation of possible differences between combined and ultrasound-only monitoring. Objectives of the present trial were independen t method comparison and bias estimation of chemiluminescent immunoassay (CL IA) versus radioimmunoassay for oestradiol, In a prospective comparison, 50 5 consecutive samples were split and assayed concurrently. Precision (repro ducibility), relative bias and logistics were analysed and compared to manu facturers' findings. Correlation between CLIA and radioimmunoassay was exce llent. Positive bias with CLIA necessitated altering decision points for th erapy. Precision (reproducibility) was superior with CLIA, making it an app ropriate candidate method for future randomized trials of the effectiveness of combined oestradiol/ultrasound monitoring for assisted reproduction.