Cytotoxicity of EDTA used in biological samples: effect on some human breast-milk studies

Ethylene diamine tetraacetic acid (EDTA) is a chelator for metal ions that has found widespread application in modern medicine and pharmacy. However, few studies have examined the cytotoxic side-effects of EDTA when added to biological samples upon various laboratory analyses. The present study was aimed at assessing the artefactual side-effects of EDTA on some biochemical assays performed on human milk samples. The secondary effects of addition of EDTA (at a final concentration of 20 mmol l(-1)) to inhibit complement system activation in human breast-milk samples were examined, using different laboratory techniques and methods, compared to milk samples with equivalent volumes of phosphate-buffered saline added. Assays considered included Biuret's test for total protein measurement, CH50 assays of whole complement activity, pH measurements and total cell counts. The toxic effects of EDTA included breast-milk cell loss, disruption of milk fat globule membrane and subsequent release of membrane-bound protein, free fatty acids and reduction in pH. It also caused false-positive results of haemolytic assays.