The effect of EDTA contaminated in sera on laboratory data

Background: We report two cases in which the data marked by low levels of serum iron (Fe) (negative value), low levels of serum calcium (Ca) and high levels of serum potassium (K) were inconsistent with their clinical states. Re-examination within I day showed that all the data were within or close to the reference intervals. These results could suggest contamination of ethylene diamine tetraacetate-dipotassium salt (K(2)EDTA) used in the blood collection tube for peripheral blood cell count in the tube for the serum. One of the mechanisms was suspected to be due to the backflow of evacuated blood mixed with K(2)EDTA into serum tube. Materials and methods: To analyze the influence of EDTA on routine and nonroutine laboratory tests, we performed routine examination using serum and EDTA plasma from healthy volunteers. Results: We found a definite effect on iron, calcium and potassium and alkaline phosphatase, zinc sulfate turbidity test, ammonia, leucine aminopeptidase and CH50. We also found a definite effects on copper, angiotensin-converting enzyme (ACE), matrix metalloproteinase (MMP)- 1, -3 and -9, tissue inhibitor of matrix metalloprotemase (TIMP)-1, hepatocyte growth factor (HGF), monoamine oxidase (MAO), vitamin B-12, ACTH and IL-6, though the mechanisms were not clear. Conclusions: Inappropriate blood collection can induced false biochemical data due to the contamination of EDTA. (C) 2002 Elsevier Science B.V. All rights reserved.