Relationship between glycosylated haernoglobin and mean plasma glucose concentration in cystic fibrosis

Background: HbA(1c) is recommended for monitoring glycaemic control in people with cystic fibrosis-related diabetes (CFRD). However the relationship between HbA(1c) and mean plasma glucose concentration (MPG) has not been established in CFRD, as in other forms of diabetes mellitus. Methods: 20 people (13 male, 29.7 +/- 8.8 years, 10 CFRD) with cystic fibrosis (CF) underwent HbA(1c) measurement and 48 h continuous glucose monitoring for estimation of MPG. The relationship between HbA(1c) and MPG was established and compared to the reported relationship for type 1 diabetes. Results: HbA(1c) was strongly correlated with MPG (R-2 = 0.888, p<0.0001) in CF. The relationship of MPG to HbA(1c) was described by the equation MPG =(1.47 x HbA(1c))- 1.15, giving a 1.47 mmol L-1 change in MPG per 1% change in HbA(1c). This equation predicts that MPG in people with CF and HbA(1c) <7.0% will be similar to MPG in people with type 1 diabetes who achieve the same HbA(1c) target. Conclusions: These results imply that HbA(1c) < 7.0% will predict good blood glucose control in CF as in type 1 diabetes. However, although HbA(1c) predicts complications in type 1 diabetes, further studies are required to establish the relationship between HbA(1c) and diabetic complications in people with CFRD. (C) 2005 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.