An elevated serum alkaline phosphatase level may decline due to specimen handling or patient therapy. This may mislead a clinician into believing that a condition causing an elevation in serum alkaline phosphatase is improving.
Specimen handling conditions that may cause an artifactual decrease in serum alkaline phosphatase activity:
(1) collection of blood into EDTA or citrate or fluoride (chelating agents will remove the Mg or Zn ions required as cofactors)
(2) exposure of the sample to excessive heat during transport (would affect heat-label isoenzymes only)
Patient factors that may cause an artifactual decrease in serum alkaline phosphatase activity:
(1) severe anemia, especially with recent blood transfusion
