Technical and financial evaluation of assays for progesterone in canine practice in the UK

The concentration of progesterone was measured in 60 plasma samples from bitches at various stages of the oestrous cycle, using commercially available quantitative and semi-quantitative ELISA test kits, as well as by two commercial laboratories undertaking radioimmunoassay (RIA). The RIA, which was assumed to be the ‘gold standard’ in terms of reliability and accuracy, was the most expensive method when analysing more than one sample per week, and had the longest delay in obtaining results, but had minimal requirements for practice staff time. When compared with the RIA, the quantitative ELISA had a strong positive correlation (r=0.97, P