Interfering effect of bilirubin on the determination of alkaline phosphatase.

OBJECTIVE This study was designed to evaluate whether the high concentration of bilirubin is able to interfere the determination of alkaline phosphatase (ALP). METHODS Clinical tests evaluating the interfering substance of bilirubin of various concentrations on the determination of ALP were conducted based upon the Clinical and Laboratory Standards Institute (CLSI) document EP7-A2, the most recent guideline on interference testing approved in 2005. RESULTS Paired t-test comparing different doses of bilirubin revealed that the concentration of 1 000 μmmol/L bilirubin negatively interfered the determination of ALP levels. The experiment designed with five different concentrations of bilirubin showed that bilirubin can exert negative interference on the measurement of ALP in a linear pattern. CONCLUSION High concentration of bilirubin can cause false measurement of ALP levels, probably interfering with the clinical prognosis of liver diseases.