Working with the hair samples in the lab is very tedious and time-consuming, but its steady rhythm often inspires us to new ideas. Sometimes, what makes this work more exciting are changing technologies we use, and that forces us to experiment to deal with these changes.
This was the case with our research on stress ecology in brown bears, in which we measure e.g. the concentration of hair cortisol and which we have carried out over the last eight years, and our colleagues from Scandinavia and Canada for much longer. The antibody in the Cortisol EIA kit (Oxford Biomedical) we have been using has changed, resulting in differences in cross-reactivity and concentrations on the standard curve. To be able to use all the data collected over the years and compare them with each other, we had to develop a method of standardizing the results after those changes. We validated this method using our data on hair cortisol concentration in bears. In this study, we cooperated with Toxicology Centre of the University of Saskatchewan in Saskatoon (Canada), Department of Veterinary Biomedical Sciences of the University of Saskatchewan (Saskatoon, Canada), Foothills Research Institute in Hinton (Alberta, Canada), the Faculty of Environmental Science and Natural Resource Management of the Norwegian University of Life Sciences and the Department of Natural Sciences and Environmental Health of the University of South-Eastern Norway.
The method we propose is easy to follow, uses simple statistics, and can be applied to any enzyme immunoassay whose sensitivity and/or accuracy has changed between kits, especially in cases where pooled quality check analyzes are not possible. Besides, this method saves lab time and costs by eliminating the need to re-analyze samples.
Our publication is available here https://www.sciencedirect.com/science/article/pii/S2215016121000042?dgcid=rss_sd_all