Effects of contamination of blood specimens with liquid potassium-EDTA anticoagulant

Abstract

Background Use of the anticoagulant EDTA, in high-concentration liquid form, in blood collection tubes can lead to cross-contamination of routine biochemistry specimens.

Spurious hyperkalaemia due to EDTA contamination: common and not always easy to identify

“…2,3 In our study, EDTA contamination was limited to samples from inpatients and general practice. It is interesting to note that EDTA contamination was not evident in samples from outpatients, which accounts for 20% of our workload and where blood samples are collected by trained phlebotomists.…”

“…2 -4 Of these, spurious hyperkalaemia is the most problematic inevitably leading to patient inconvenience, but may also lead to mismanagement of the patient. 3,5 There is little data in the literature relating to the prevalence of sample contamination with EDTA. As part of a service evaluation, we measured EDTA in hyperkalaemic samples to identify EDTA contamination and further analysed all the samples for calcium, zinc, magnesium and alkaline phosphatase to study whether these could act as surrogate markers to reliably identify EDTA contamination.…”

EDTA analysis on the Roche MODULAR® analyser

“…2 In this laboratory, the current workload includes 400,000 potassium analyses per year. As a relatively arbitrary cut-o¡, unhaemolysed specimens with potassium 45.5 mmol/L are automatically analysed for the presence of EDTA.…”

“…1,2 To avoid misinterpretation of biochemical ¢nd-ings, a rapid technique to detect low-level EDTA contamination is required. 2 In an ethanol acetate bu¡er (pH 4.8) EDTA abstracts copper ions from a violet-coloured pyridylazonaphtholcopper (PAN-Cu) complex to yield yellow-coloured free PAN. The decrease in solution absorbance as the complex is de-coppered by EDTA is proportional, in a non-linear fashion, to the EDTA concentration in the sample.…”

A Man with Recurrent Fractures and Foot Pain

“…Zinc and magnesium deficiency, which are both cofactors of the enzyme ALP, are known causes and always should be excluded (4 ). Contamination with the anticoagulant EDTA, which can chelate both magnesium and zinc, reduces the activity of ALP in serum (5 ). Medications such as bone antiresorptives can result in hypophosphatasemia (4 ).…”