Interpretation of HbA in primary care and potential influence of anaemia and chronic kidney disease: an analysis from the Copenhagen Primary Care Laboratory (CopLab) Database.

AIMS

To investigate, in a large population in primary care, the relationship between fasting plasma glucose and HbA measurements, as well as the clinical implications of anaemia or chronic kidney disease for the interpretation of HbA values.

METHODS

From a primary care resource, we examined HbA and fasting plasma glucose as well as haemoglobin and estimated GFR. We stratified observations by chronic kidney disease stage and anaemia level. The estimation of the mean fasting plasma glucose level from HbA alone, and from HbA , haemoglobin and estimated GFR, respectively, was evaluated.

RESULTS

In 198 346 individuals, the fasting plasma glucose-HbA relationship mimicked the regression described in the A1c-Derived Average Glucose (ADAG) study, which was based on average capillary and interstitial glucose. The fasting plasma glucose-HbA relationship was unaffected in mild to moderate chronic kidney disease and in mild to moderate anaemia. The correlation changed only in severe hyperglycaemia and concurrent severe anaemia or when estimated GFR was <45 ml/min/1.73m², so that glucose concentration was underestimated by HbA in anaemia and overestimated in chronic kidney disease. The prevalence of estimated GFR <30 ml/min/1.73m² was 0.82%, while the prevalence of haemoglobin <81 g/l (5.0 mmol/l) was 0.11%.

CONCLUSIONS

The relationship between fasting plasma glucose and HbA mimics that of the people with diabetes included in the ADAG study. Mild to moderate anaemia and CKD do not have a significant impact on the interpretation of HbA as a marker of retrograde glycaemia. Hence, it seems justified to use HbA without adjustment in primary care.