Understanding the relationship between the frequency of HbA1c monitoring, HbA1c changes over time, and the achievement of targets: a retrospective cohort study

Abstract

Abstract Background The goal of post-diagnosis diabetes management is the achievement and maintenance of glycaemic control. Most clinical practice guidelines recommend 3–6 monthly HbA1c monitoring. Despite this guidance, there are few data supporting the impact of monitoring frequency on clinical outcomes, particularly from low- and middle-income country settings. This study examined associations between adherence to monitoring recommendations and the achievement of HbA1c targets, and HbA1c changes, over time in a South African cohort. Research Design and Methods: The study utilised routinely collected HbA1c test data on patients with diabetes aged ≥ 18 years in the Western and Northern Cape between 2015 and 2020 to examine the relationship between mean change in HbA1c values and the duration between consecutive HbA1c tests (retest interval). The monitoring adherence rate, which represents the proportion of intervals between consecutive tests that met South Africa’s guideline recommendations, was calculated for each patient. Multistate modelling and linear mixed-effects modelling were then used to examine the effect of monitoring adherence on the achievement of glycemic control targets and longitudinal changes in HbA1c. Results The 132,859 diabetes patients with repeat tests had a median of three HbA1c test requests, a median follow-up time of 2.3 years and a median retest interval of 10.3 months. A retest interval 2–4 months maximised the downward trajectory in HbA1c, while individuals with low adherence to the monitoring guidelines were the least likely to achieve glycaemic control in one year. Moreover, patients with low monitoring adherence had higher mean HbA1c levels compared to patients with moderate or high monitoring adherence. Conclusions The results illustrated the importance of adherence to monitoring recommendations as adherent patients had better glycaemic control and lower mean HbA1c levels over time.