Introduction: Worldwide guidance advocates regular HbA1c testing for people with diabetes mellitus, usually 2-4/yr. We previously showed that HbA1c testing frequency is linked to outcome in terms of HbA1c control. Here we examine the effect of variability (standard deviation = SD) in test interval on change in HbA1c over 7 yrs (Jun 2012-Jul 2019) using laboratory data.
Methods: We focused on people with HbA1c within the first 2 years who also had a HbA1c 5 years± 3 months later and ≥6 tests (total 23582 people). We grouped cases based on the number of tests between t0and t0+5yrsand calculated the SD decile for each group. We examined the link between SD deciles and DHbA1c level,stratifying by starting HbA1c.
Results: We showed that higher variability in testing frequency was linked to worsening HbA1c control. This effect was most evident in those with lower starting HbA1c levels. In those with a starting HbA1c of <59mmol/mol, the lowest SD decile was associated with an increase in mean HbA1c of 3.9mmol/mol while for those with the highest decile, it was more than double this (7.9mmol/mol). In those with an initial HbA1c of 59-75mmol/mol, the lowest SD decile had a mean reduction of 3mmol/mol, while those in the highest decile showed a 4mmol/mol rise. In those with starting values of >75mmol/mol, the same trends were seen, but were less marked. These effects were independent of testing interval. Mean HbA1c level increased with increasing SD decile, irrespective of starting HbA1c (P = 0.009).
Conclusion: These findings indicated that HbA1c testing consistency/regularity, not just numbers of tests/yr, is important in maintaining diabetes control, especially in those with on-target HbA1c levels. This has implications for the management of people who attend sporadically for testing and suggests the need for developing systems to improve regularity of testing.
08 Nov 2021 - 10 Nov 2021