Natural HbA1c variability can obscure treatment effects
medwireNews: A single glycated hemoglobin (HbA1c) measurement will not be sufficient to gauge treatment effects or the need for intensification in many type 2 diabetes patients, research shows.
The study from the MASTERMIND consortium reveals high HbA1c variability over time in individual patients, particularly in those with poor glycemic control.
“HbA1c bounces up and down in most of our patients,” said Andrew McGovern (University of Exeter Medical School, UK), who presented the findings in a poster session at the 54th EASD Annual Meeting in Berlin, Germany.
“And all our guidelines suggest changing, uptitrating therapy on a single value. But in those patients where the risks and benefits of increasing their therapy [are] not that clear, it may be worth just waiting.”
He suggested that an element of clinical inertia could be accounted for by physicians being aware of HbA1c variability and waiting for longer-term trends to become clear before acting.
The team used data from 2589 patients in the ADOPT trial and 53,108 from the UK Clinical Practice Research Datalink (CPRD), looking at the variability across four consecutive HbA1c measurements, taken 3 months apart for ADOPT and 6 months apart for the CPRD.
They found that HbA1c variability, defined as the standard deviation of these four measurements, was high overall. Even for people with relatively low measurements, of around 45 mmol/mol (6.3%), the standard deviation was approximately 5 mmol/mol (2.6%), said McGovern.
“So what that means is that between two successive HbA1c values, 30% – around a third of people – will have an HbA1c increase or decrease of more than half a percent,” he said. “And that’s with no medication changes.”
And at higher HbA1c levels the difference between two consecutive measurements could be as much as 1%, he added.
The team found that higher HbA1c variability was associated with older age, being male, Black ethnicity, and use of sulfonylureas in both cohorts, and with high BMI in the CPRD cohort. However, McGovern noted that these factors explained only about 10–15% of the variability, with most left accounted for.
“So a lot of this glycemic variability is not explained by these clinical characteristics,” he said, adding that HbA1c variability “seems to be a universal feature.”
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