Interference with Immunoassays of a Neonate on High Biotin: Case Report and Literature Review

Biotin is sometimes administered in mega doses to children to treat certain inborn errors of metabolism. We report the case of a one-week-old newborn who was started on a ‘mitochondrial cocktail’ that contained a high dose of biotin. On day seven of life, his thyroid function test showed a biochemical picture of primary hyperthyroidism, which was not clinically evident. The suspicion of immunoassay interference with thyroid function test was confirmed when another lab, using a different immunoassay, gave normal results. If the biochemical profile does not match the clinical picture, it is reasonable to doubt the test result and think of assay interference.