Proof of concept: stabilized whole blood material suitable for external quality assessment of near-patient testing devices

Abstract Objectives Even though reliable glucose concentration measurements are essential in diagnosis and monitoring of diabetes mellitus, external quality assurance based on mandatory reference method values can only be conducted to a limited extent for measurements in whole blood. The reason is the lack of stabilized whole blood materials suitable for the application in glucose measurement devices used in near-patient testing. Methods Two patented whole blood stabilizers were tested using four commercially available near-patient testing devices and one patient self-testing device for plasma-referenced glucose measurements. Furthermore, a laboratory method for plasma-glucose measurements was included. Venous whole blood samples from 30 apparently healthy volunteers were used. Two whole blood samples (stabilizer A and B) per subject were kept at room temperature over the study period of seven days and aliquots were taken each day from the original sample for measurement on all devices. After venous puncture, left over whole blood from the collection system was used for immediate glucose measurements without stabilizer on the near-patient testing devices. Results Each investigated device gave stable results at least for one of the two stabilizers for a period of four days. Imprecision based on quality controls ranged between 1.7 and 4.8 % coefficient of variation for near-patient testing devices, but did not reflect observed variability in measurement results from stabilized and unstabilized whole blood in one device. In addition, a considerable deviation of 0.8 mmol/L was observed among the near-patient testing devices underlining the need for reference method values in external quality control. Conclusions Our study provides proof of concept that for each investigated device at least one stabilizer of glucose in whole blood shows a good performance for at least four days. Therefore, these stabilizers appear to be suitable candidate materials for external quality assessment of near-patient testing devices.