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A response by Alyce S. Adams et al. to a letter to the editor about their article on race differences in long-term diabetes management is presented.

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.

Objective: To compare glycosylated hemoglobin (GH) results obtained by filter paper fingerstick collection and mailed for assay by affinity chromatography with results from a venous sample assayed by ion-exchange chromatography (HbA1) in a local laboratory., Research Design and Methods: Fifty-eight volunteer subjects with insulin-dependent diabetes mellitus (IDDM), aged 5-24 yr, included patients at a referral-based IDDM clinic and subjects in an ongoing research study. We obtained two blood samples from each subject. One was collected by fingerstick onto filter paper, the other by venipuncture into a vacutainer. We sent filter paper samples to the Diabetes Research Laboratory (Univ. of Missouri, Columbia, MO) for analysis. Vacutainer samples were sent to the Clinical Chemistry Department of the Clinical Laboratory, University of Colorado Health Sciences Center., Results: Results were highly correlated (r = 0.89, P = 0.0001). Fifty-nine percent were classified identically when results were normalized to SD units and grouped to suggest levels of clinical concern., Conclusions: The filter paper method is a convenient, accurate measure of glycosylated hemoglobin in young people with IDDM. It should be considered a credible alternative research and clinical tool.

It would be advantageous to be able to measure glycosylated hemoglobin (GHb) from a sample of blood dried on paper and sent to the physician by the patient. Indeed, such a technique has been introduced by Isolab (Akron, OH). We tested the validity of the method to determine whether applying the blood to paper and immediately assaying it correlates with the same sample assayed by the usual whole-blood technique, the size of sample applied to paper affects apparent GHb results, time and temperature of storage of the sample paper affect apparent GHb results, and plasma glucose concentration of the sample affects GHb results. The GHb of samples assayed immediately after application to sample paper versus those assayed as whole blood showed very good correlation (r = .93, P less than .001). Volume of the drop of blood applied to paper (25-100 microliters) did not affect results. However, there was a dramatic, temperature-dependent increase in apparent GHb when samples were stored on sample paper, averaging 12.5, 16.3, and 19.5% when stored at room temperature for 3, 6, and 9 days, respectively. Overall, apparent GHb rose from 1.3-fold in 3 days at 4 degrees C to 3.8-fold in 9 days at 37 degrees C. The rate of GHb formation was proportional to plasma glucose concentration, but removal of free glucose by ethanol or glucose oxidase did not yield consistent results for this method. We conclude that these sample papers are not useful as an approach to collecting blood samples for GHb measurement.