Appropriate glycated haemoglobin testing frequency to monitor patients with type 2 diabetes

Abstract

Glycated haemoglobin (HbA1c) is used to monitor glycaemic control among patients with type 2 diabetes (T2DM). Glycated haemoglobin represents a 3-month glycaemic average, with the most recent 6 weeks of glycaemia having the greatest influence. Analytical and biological variation introduce imprecision into any single HbA1c, where a result of 7.5% may represent a ‘true’ value between 6.8% and 8.2%. This Therapeutics Letter evaluates the most appropriate interval for monitoring HbA1c in T2DM. Evidence was synthesised from a pragmatic randomised controlled trial (RCT) and three large observational studies. In the RCT, 94% of patients monitored every 6 months maintained good glycaemic control compared to 92% of those monitored every 3 months. Observational data indicated that 3-month testing resulted in a clinically unimportant difference in HbA1c compared with 6-month testing. Furthermore, patients tested 2–3 times annually were as likely to achieve personalised goals as those tested four times per year. Testing more than four times annually was associated with a lower probability of achieving targets. For patients with stable T2DM meeting glycaemic goals, monitoring HbA1c every 6 months is as effective as every 3 months and could be contemplated for many patients following a discussion of patient goals and preferences. Frequent testing may be reserved for periods of medication adjustment, changes in health status or when targets are unmet. Reducing testing frequency in stable patients minimises low-value data, reduces the carbon footprint of lab testing and improves patient convenience without compromising clinical outcomes.