Effect of sample instability on glycohemoglobin (HbA1) measured by cation-exchange chromatography

We compared results for glycohemoglobin obtained from fresh whole blood or separated erythrocyte samples with results obtained after storage. We judged the storage condition to be acceptable ("stable") if the glycohemoglobin results after storage were within the 95 confidence interval (+/- SD) of the results obtained for the specimens on the day of venipuncture. Hemolysates can validly be stored for five months at -70 degrees C. Whole-blood samples stored at 4 degrees C remain stable for four days; whole blood treated with heparin or EDTA (but not oxalate) is stable for seven days. At 30 degrees C, whole blood or erythrocytes from some donors are stable for one day, but after two days and seven days, results are frequently higher. We confirmed previous findings that the separated erythrocytes can be stored at -20 degrees C for at least seven days. In addition, we compared the elution profiles for stored samples showing increased values.