The sample was tested further for free biotin concentrations and the result was approximately 304 ng/ml.This concentration was considerably above the allowable biotin concentration that is specified in product labeling for the assay.In addition, the patient also received furosemide.It is known that this drug causes elevated ft4 values if taken at the daily therapeutic dosage level.This information is documented in product labeling.Both the high level of biotin and the effect of the drug furosemide most likely had an impact on the ft4 assay values.From the provided information, a general reagent issue could most likely be excluded.
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