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Interpretation of HbA 1c : association with mean cell volume and haemoglobin concentration
Author(s) -
Simmons D.,
Hlaing T.
Publication year - 2014
Publication title -
diabetic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.474
H-Index - 145
eISSN - 1464-5491
pISSN - 0742-3071
DOI - 10.1111/dme.12518
Subject(s) - medicine , diabetes mellitus , endocrinology , fasting glucose , creatinine , insulin resistance
Aim The utility of HbA 1c in diabetes diagnosis is reduced in settings associated with altered haemoglobin glycation. We have studied whether HbA 1c varies with mean cell volume and mean cell haemoglobin concentration as measures of haemoglobin metabolism. Methods Randomly selected adults from rural Victoria, Australia, were invited for biomedical assessment. After excluding patients with known diabetes and/or serum creatinine ≥ 0.12 mmol/l, 1315 adults were included. Demography, arthropometric measurements, oral glucose tolerance test, analyses of full blood count and HbA 1c were undertaken. Results After adjusting for age, sex, ethnicity, BMI , town and socio‐economic status, there were no significant differences in haemoglobin, mean cell volume or mean cell haemoglobin concentration by glycaemic status (defined by oral glucose tolerance test). HbA 1c was significantly and independently associated with fasting glucose, town, mean cell haemoglobin concentration, ethnicity, age and BMI among men < 50 years ( R 2 = 33.8%); fasting glucose, 2‐h glucose, mean cell haemoglobin concentration and town among men ≥ 50 years ( R 2 = 47.9%); fasting glucose, mean cell volume, mean cell haemoglobin concentration, town, 2‐h glucose and age among women < 50 years ( R 2 = 46.3%); fasting glucose, mean cell haemoglobin concentration, mean cell volume and 2‐h glucose among women ≥ 50 years ( R 2 = 51.6%). A generalized linear model showed a gradient from an adjusted mean HbA 1c of 36 (95% CI 34–38) mmol/mol with a mean cell haemoglobin concentration of ≤ 320 g/l to 30 (95% CI 29–31) mmol/mol with a mean cell haemoglobin concentration of > 370 g/l. The gradient across mean cell volume was negative, but only by 1 mmol/mol (0.1%) HbA 1c . Conclusion A mean HbA 1c difference of 5 mmol/mol (0.5%) across the mean cell haemoglobin concentration reference range suggests that an accompanying full blood count examination may be required for its use in the diagnosis of diabetes. Further studies are required to confirm this.