Ethylene glycol-stabilized haemolysates for glycated haemoglobin assay. Further analytical investigations and applications to quality control programmes.

The direct effect of the ethylene glycol on the quantitation of glycated haemoglobins by ion-exchange minicolumn chromatography, affinity chromatography and high performance liquid chromatography was investigated. No evident effect was found for ethylene glycol concentrations between 0.0 and 0.5 (volume fraction). The ethylene glycol-stabilised haemolysates were also analysed by HPLC: the elution profiles were similar to those of haemolysates fresly prepared from whole blood, and they remained unchanged, even after 18 months of storage at -20 degrees C. A preliminary inter-laboratory trial among 15 Italian laboratories was organized, using these ethylene glycol-stabilised haemolysates and, for comparison, a lyophilized commercial preparation. From the data obtained in this trial we confirmed the validity of using ethylene glycol-stabilized haemolysates as control materials, both for intra- and inter-laboratory standardization of glycated haemoglobin measurements.