Changes in dried blood spot Hb A1c with varied postcollection conditions.

Diabetes affects Ͼ5% of US adults (15% of those older than 60 years) and is on the rise in adolescents. Gly-cosylated hemoglobin (Hb A 1c), a cumulative marker of blood glucose concentrations over the previous 2 months, has become a powerful clinical tool for diabetes management (1, 2) and is predic-tive of future complications of diabetes (3). Large-scale community-based studies often preclude the option of phlebotomy and would benefit from simplified sample handling. Epidemiologic studies have begun to use Hb A 1c in dried blood spots as a biomarker (4). We studied Hb A 1c from dried blood spots by validating the storage conditions appropriate for large-scale epidemiologic/outreach studies to test the hypothesis that measurements of Hb A 1c in dried blood spots are valid under low-intensity storage conditions. All participants were studied at the Brigham and Women's Hospital , Boston, Massachusetts; all procedures were conducted in accordance with the Declaration of Helsinki. Blood samples were drawn via standard phlebotomy procedures into EDTA-containing tubes for duplicate HPLC analyses of Hb A 1c (Tosoh G7 automated HPLC assay, Brigham and Women's Hospital Hematology Laboratory). Intrarun impreci-sions (CVs) were 0.5% and 0.9% at Hb A 1c proportions of the total hemoglobin of 0.041 and 0.1335, respectively. Interrun CVs were 1.6% for control samples with Hb A 1c values of 0.064 and 0.7% for control samples with Hb A 1c values of 0.11. Blood for spotting was drawn into an identical EDTA tube, and a syringe was used to let each drop of blood fall onto randomly assigned blood-spot cards (3 spots/card) within 1 min. Inversion of the syringe minimized the settling of red blood cells. Samples were air-dried for at least 20 min and then placed into single-sample, airtight bags that included a desic-cant pouch. Trios of blood-spot cards were processed identically. After storing the samples at room temperature for 0, 2, or 4 weeks, we shipped the samples to Biosafe Laboratories for Hb A 1c analysis (conditions 1–3) or placed them in freezer storage (Ϫ80 °C) for an additional 4 or 12 weeks (conditions 4 – 6, 7–9). Sample trios were shipped by US mail, presumably at room temperature, in batches that included multiple individuals/conditions per package. Hb A 1c measurements of dried blood spots were performed blinded to storage conditions and protocol. We used Roche HbA 1c Hemolyzing Re-agent to elute from 3.00-mm punches of homogeneous parts of the blood …