External quality assessment in primary health care by using fresh whole blood.

Desktop analyzers and single-test meters used in primary healthcare are mainly calibrated to measure whole blood. To minimize matrix effects of control materials in external quality assessment schemes, we stabilized fresh human EDTA-treated blood with sodium iodoacetate (1.8 mmol/L). The whole-blood based control material was useful for control of hemoglobin and glucose, the two most common analyses in primary care, even after storage at room temperature for at least 10 days and at 5 degrees C for 3 weeks. The material was also useful for control of cholesterol and creatinine analyses for samples stored as long as 3 days at ambient temperature.