OBJECTIVES: To determine the cause of discrepancies in the alkaline phosphatase (ALP) activities of quality control (QC) materials in two different analyzers using IFCC method. DESIGN AND METHODS: ALP activities of patients' samples and QC materials (QC1 and QC2 from Bio-Rad) measured using TBA-200FR and Synchron LX-20 analyzers were compared and isoenzyme electrophoresis was done. Fractional mixing of bone or liver ALP with placental ALP was performed. ALP activities of QC materials were measured in TBA-200FR with pH-modified reagents. RESULTS: ALP activities of QC materials were significantly lower in TBA-200FR than in LX-20. Placental ALP comprised 57% of QC1 and 95% of QC2. Higher placental ALP proportion in the mixture with bone or liver ALP resulted in lower ALP activities in TBA-200FR. The discrepancy in ALPs of QC materials decreased when measured with pH-modified reagents. CONCLUSION: Placental ALP in QC materials and differences in reagents' pH caused the discrepancy in ALP activities.
OBJECTIVES: To determine the cause of discrepancies in the alkaline phosphatase (ALP) activities of quality control (QC) materials in two different analyzers using IFCC method. DESIGN AND METHODS: ALP activities of patients' samples and QC materials (QC1 and QC2 from Bio-Rad) measured using TBA-200FR and Synchron LX-20 analyzers were compared and isoenzyme electrophoresis was done. Fractional mixing of bone or liver ALP with placental ALP was performed. ALP activities of QC materials were measured in TBA-200FR with pH-modified reagents. RESULTS:ALP activities of QC materials were significantly lower in TBA-200FR than in LX-20. Placental ALP comprised 57% of QC1 and 95% of QC2. Higher placental ALP proportion in the mixture with bone or liver ALP resulted in lower ALP activities in TBA-200FR. The discrepancy in ALPs of QC materials decreased when measured with pH-modified reagents. CONCLUSION: Placental ALP in QC materials and differences in reagents' pH caused the discrepancy in ALP activities.