The determination of aspirin levels in the presence of hyperbilirubinemia.

Many major medical centers are presently utilizing a shortened method (Keller) for determining serum aspirin levels which does not remove interfering compounds. This report documents that the presence of even 1 mg of bilirubin/dl of serum is sufficient to cause a falsely high aspirin level. It is suggested that any method for determining serum bilirubin which does not remove interfering substances constitutes a danger to many groups of patients and should be discontinued.