Capillary Blood on Filter Paper for Determination of HbA1c by Ion Exchange Chromatography

OBJECTIVE: To facilitate HbA1c determination, we evaluated an HbA1c filter paper system enabling capillary blood sampling at home by the patients. RESEARCH DESIGN AND METHODS: Capillary blood (two drops) was applied to a filter paper (HbA1c Via Post) and sent to the laboratory where a small disc was punched out on the filter paper. Hemoglobin was eluted from the disc in a buffer containing cysteine to eliminate the interfering glutathione adduct (HbA3) formed during storage. Analysis was performed by ion-exchange chromatography (Mono S, high-performance liquid chromatography), and the eluate was compared with hemolysate of venous blood from 41 patients. The stability of blood impregnated on filter paper was checked at different temperatures over different periods of time. RESULTS: There was an excellent agreement (r = 0.99) between HbA1c values from capillary blood on filter paper and HbA1c values from venous blood. HbA1c values were constant when stored on filter paper for 5-7 days at 20-21 degrees C (room temperature) or at 4-6 degrees C (refrigerator) for 10 days as well as at -70 degrees C for several months after blood sampling. A new chromatographic-interfering hemoglobin fraction both from venous and capillary samples was identified as free alpha-chain of hemoglobin. CONCLUSIONS: The HbA1c filter paper system enables capillary blood sampling at home, eliminates the need of vein puncture in children and adults, and provides the diabetologist with an HbA1c value when the patient visits the clinic without a need for a previsit phlebotomy.