A new systematic review has highlighted the effects of anaemia and iron deficiency on HbA1c levels, which may lead to inaccuracies when using the measurement to diagnose diabetes. With recent studies indicating that approximately 30% of pregnant women have anaemia, this translates to a significant number of people in whom measuring HbA1c levels, as recommended by the both the World Health Organization (WHO) and the American Diabetes Association (ADA), can lead to a false-positive diagnosis of diabetes.
The authors of the review identified 12 studies on the impact of anaemia on the WHO/ADA-recommended HbA1c cut-off point of 48 mmol/mol (6.5%). In general, these studies showed that iron deficiency, with or without anaemia, resulted in increased HbA1c levels compared with controls without iron deficiency, despite the fact the blood glucose levels remained the same.
Pointing out the small numbers of eligible studies in their review, the authors call for more research on this topic, saying, “The key questions that are still to be answered are whether anaemia and red blood cell abnormalities will have a significant impact on the diagnosis of diabetes using HbA1c in the general population – something that is now widely performed.”
In the meantime, they make the following recommendations:
- When screening for diabetes, if glucose and HbA1c measurements give different results, consider abnormalities related to anaemia or iron deficiency.
- Iron deficiency and anaemia may be sufficient to cause a change in HbA1c values; this is highly relevant in women of childbearing age.
- If abnormalities such as anaemia are identified, consider correction of the abnormality (e.g. by using iron supplementation) before using HbA1c for diagnosing or monitoring diabetes. The findings in this review suggest that it may take up to 6 months after treatment is initiated to normalise haemoglobin levels.
The study can be read in full here.
