Effects of sample dilution, peroxidase concentration, and chloride ion on the measurement of unbound bilirubin in premature newborns

Bfss measured by the UB Analyzer at the standard 42-fold sample dilution using assay buffer without Cl− and a single peroxidase concentration is significantly less than the Bfeq in undiluted plasma. Accurate Bf measurements can be made only in minimally diluted serum or plasma.