[Chronic kidney failure and biotin: A combination inducing unusual results in thyroid and parathyroid investigations, report of 2 cases].

In clinical chemistry, many immunoassays apply biotin and streptavidin in the assay principle. Presence of high levels of biotin in patient samples can produce negative or positive interference depending on the assay format. In this study, we describe 2 clinical cases with chronic kidney failure and with unusual thyroid and parathyroid function test results due to biotin interference.