Background

H₂O₂ is supposed to be part of the laboratory test panel for assessment of oxidative stress. This molecule contributes to oxidative stress by reacting with Fe²⁺ ions to produce hydroxyl radicals. Anticoagulants, including citrate and EDTA chelate Fe²⁺, possibly have implications in oxidative stress studies especially when H₂O₂ is measured.

Objective

This brief commentary is on the measurability of H₂O₂ in citrated and EDTA blood samples.

Method

Laboratory evaluation was performed using blood samples of 30 sheep collected in EDTA and citrate tubes. Samples were centrifuged, and plasma separated. H₂O₂ was determined using the Biotech H₂O₂ 560 assay protocol on plasma. The ratio of EDTA to iron was also estimated to help interpret levels of H₂O₂ in EDTA blood.

Results

There was measurable H₂O₂ reaction in citrate samples, but not in the EDTA blood. Based on brand sterile hematology tubes containing 1.8 mg EDTA per mL blood; approximately 4:1 ratio of EDTA to iron is estimated. Presuming this calculated ratio is a reflection of the true iron levels in the sheep's blood, the test results support the suggestion that ratio of EDTA to iron is greater than 1:1.

Conclusion

Evidence is hereby presented to advance that EDTA anticoagulant is unsuitable for laboratory testing of H₂O₂ in plasma. Further studies may be needed to ascertain the effects of different anticoagulants on H₂O₂ in whole blood and haemolysate to see how these can be compared to plasma. This is relevant to establish a standard protocol for integration of H₂O₂ test for assessment of full oxidative stress panel in clinical practice.