Maximising the cost-efficiency of assay procedures

Cortisol concentrations were measured in cattle plasma and pig muscle juice samples obtained from groups of animals slaughtered at different abattoirs. Statistically significant (P < 0·001) differences were obtained for between-abattoir comparisons for both the cattle and pig samples. Cortisol concentrations were determined using a radio-immunoassay kit. In accordance with the instructions, assays were performed in duplicate. An analysis of variance indicated that the use of a single determination on more samples, instead of duplicate determinations of fewer samples, would have led to an important increase in accuracy for detecting differences between means. It would have been more cost-efficient to collect additional samples and perform one assay only on each sample.