Reduced Testing Frequency for Glycated Hemoglobin, HbA1c, Is Associated With Deteriorating Diabetes Control

Abstract

OBJECTIVE We previously showed that in patients with diabetes mellitus, glycated hemoglobin (HbA1c) monitoring outside international guidance on testing frequency is widespread. Here we examined the relationship between testing frequency and diabetes control to test the hypothesis that retest interval is linked to change in HbA1c level. RESEARCH DESIGN AND METHODS We examined repeat HbA1c tests (400,497 tests in 79,409 patients, 2008–2011) processed by three U.K. clinical laboratories. We examined the relationship between retest interval and 1) percentage change in HbA1c and 2) proportion of cases showing a significant HbA1c rise. The effect of demographics factors on these findings was also explored. RESULTS Our data showed that the optimal testing frequency required to maximize the downward trajectory in HbA1c was four times per year, particularly in those with an initial HbA1c of ≥7% (≥53 mmol/mol), supporting international guidance. Testing 3-monthly was associated with a 3.8% reduction in HbA1c compared with a 1.5% increase observed with annual testing; testing more frequently provided no additional benefit. Compared with annual monitoring, 3-monthly testing was associated with a halving of the proportion showing a significant rise in HbA1c (7–10 vs. 15–20%). CONCLUSIONS These findings provide, in a large, multicenter data set, objective evidence that testing outside guidance on HbA1c monitoring frequency is associated with a significant detrimental effect on diabetes control. To achieve the optimum downward trajectory in HbA1c, monitoring frequency should be quarterly, particularly in cases with suboptimal HbA1c. While this impact appears small, optimizing monitoring frequency across the diabetes population may have major implications for diabetes control and comorbidity risk.

Resource use associated with type 2 diabetes in Africa, the Middle East, South Asia, Eurasia and Turkey: results from the International Diabetes Management Practice Study (IDMPS)

“…For example, increases in screening for complications, HbA1c testing, SMBG, diabetes education and medication use are linked to positive long-term health benefits and can lead to cost savings 4142 In a recent analysis of a large clinical laboratory database, patients who had three-monthly measurements of HbA1c were found to have the best glycemic control 42. In a 7-year prospective survey of Chinese patients with T2D, lack of monitoring of HbA1c and/or lipids was associated with a 15-fold increased risk of death compared with those who had at least one measurement 43.…”

ISPAD Clinical Practice Consensus Guidelines 2018: Glycemic control targets and glucose monitoring for children, adolescents, and young adults with diabetes

“… Facilities for HbA1c measurement should be available to all centers caring for young people with diabetes. Every child should have a minimum of four measurements per year (at approximately 3‐month intervals) Capillary blood collection is preferable.…”

Timings for HbA1c testing in people with diabetes are associated with incentive payments: an analysis of UK primary care data

“…Previous reports have described HbA 1c testing practices in UK primary care [8,11,26], with outcomes ranging from the numbers of inappropriate test requests [8] to implications of testing frequency on HbA 1c change [11,26]. Re-testing HbA 1c within very short time intervals may be appropriate for some individuals who had recently been prescribed a new medication to monitor response or adherence [6].…”