Shortfalls of the use of HbA1C-derived eAG in older adults with diabetes.
OBJECTIVE
The hemoglobin HbA1C (HbA1C) value, translated into estimated average glucose concentration (eAG), is commonly used to assess glycaemic control and manage treatment regimens in people with diabetes. However, the relationships among HbA1C-derived eAG, and mean glucose concentration derived from continuous glucose monitoring (CGM) in different populations have not been well studied. We examined this relationship in older people with diabetes and compared the results to those currently used in clinical practice.


METHODS
Data from three studies evaluating CGM in older adults (≥70 years of age), with stable glycaemic control were analyzed retrospectively. Mean glucose and mean amplitude of glucose excursion (MAGE) were calculated from CGM data and correlated with HbA1C and HbA1C-derived eAG using the ADAG study formula.


RESULTS
HbA1C and CGM data were analyzed from 90 patients with mean age 76±5 years, HbA1C 7.9±1.2% (63±13 mmol/mol) and 77% with Type 2 diabetes. The HbA1C and HbA1C-derived eAG correlated significantly with CGM-measured mean glucose (r(2)=0.30, p<0.0001) and MAGE (r(2)=0.16, p=0.00013) in this population and all its subgroups, but the slopes of the relationship between HbA1C and eAG or CGM-measured mean glucose were significantly different.


CONCLUSIONS
HbA1C-derived eAG values may not accurately reflect CGM-measured mean glucose or MAGE in older adults with diabetes. Wide glucose excursions should be considered and HbA1C should be interpreted cautiously when making treatment changes based on HbA1C.
Joslin Diabetes Center, United States; Beth Israel Deaconess Medical Center, United States; Harvard Medical School, United States. Electronic address: medha.munshi@joslin.harvard.edu.
M N
MN
Munshi
Joslin Diabetes Center, United States; MCPHS University, United States.
A R
AR
Segal
Joslin Diabetes Center, United States.
C
C
Slyne
Akdeniz University, Turkey.
A A
AA
Samur
Tufts University School of Medicine, United States.
K M
KM
Brooks
Joslin Diabetes Center, United States; Harvard Medical School, United States.
E S
ES
Horton
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000379:methods / Q000592:standards; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000628:therapy; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000628:therapy; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013223:Statistics as Topic / Q000379:methods
D001786:Blood Glucose; D006442:Glycated Hemoglobin
Diabetes; Estimated average glucose (eAG); HbA1c; Older adults