Interpretation of hemoglobin A(1c) (HbA(1c)) values among diabetic patients: Implications for quality specifications for HbA(1c)

Background: Few studies have examined patients' views, knowledge, and under standing of glycohemoglobin A(1c) (HbA(1c)) testing. We explored such issue s in patients with type 1 diabetes and used their statements to estimate an alytical quality specifications for HbA(1c) testing. Methods: We recruited 201 patients from a hospital outpatient clinic. A que stionnaire was used to collect information on diabetes characteristics, per ceived knowledge of HbA(1c), last HbA(1c) value, HbA(1c) target value, and thresholds for action. Patients were asked to indicate the magnitude of cha nge in HbA(1c) from 9.4% that they would consider to be a true (real) chang e; from their responses, we calculated patient-derived quality specificatio ns for HbA(1c). Results: Fifty-eight percent of the patients felt they had "high" knowledge about HbA(1c) and > 80% of responders knew their last HbA(1c) value, their target HbA(1c), and the threshold value of HbA(1c) for treatment intensifi cation. The mean acceptable HbA(1c) value was 7.5%. Patients with lower val ues on their most recent tests reported lower target values for HbA(1c) and lower values for the upper HbA(1c) threshold for treatment intensification . An analytical CV (CV,) of 3.1% would be satisfactory for 75% of patients when HbA(1c) is increasing (80% confidence), and a CVa of 3.2% would be sat isfactory for 75% when HbA(1c) is decreasing (95% confidence). Conclusions: Type 1 patients' perceived knowledge about HbA(1c) testing is high. They are well informed about their own personal results and about tar get values and the upper HbA(1c) threshold for action. The patient-derived analytical quality specification for imprecision (CV) is 3.1%. (C) 2001 Ame rican Association for Clinical Chemistry.