Testing the Limits on Blood Glucose Monitoring: Can We Safely Cut Back?

Is self-monitoring of blood glucose (SMBG) cost-effective? There is no question that achieving good glycemic control is one means to decrease diabetes-related complications.¹ SMBG is often recommended to help guide treatment decisions.  Consumer-oriented advertising often promotes frequent SMBG as means to achieve better glycemic control but current clinical practice guidelines do not provide specific recommendations regarding the frequency of blood glucose monitoring.

The clinical effectiveness of SMBG is unclear, particularly in non-insulin treated patients.² Several systematic reviews and meta-analyses have shown SMBG at least once daily leads to statistically significant but perhaps not clinically important reductions in hemoglobin A1C (A1C) (0.25-0.35%).^2,3 Over $1.3 billion dollars were spent on SMBG testing supplies for US Medicare patients in 2012.⁴

The lack of conclusive evidence supporting the clinical benefits of routine SMBG combined with the rising costs of healthcare has led some payers to place limits on SMBG testing supplies.⁵ Proponents of frequent SMBG state that limiting testing supplies would lead to worsened glycemic control and poor health outcomes. But is this really true? With the potential for considerable costs savings, should SMBG supply limits be instituted for patients who do not require insulin therapy?

A study was conducted in Canada to determine the effects of limiting SMBG supplies in patients enrolled in the Ontario public drug program.⁵ The program is similar to the US Medicare/Medicaid system (eligibility based on age 65 or older or pre-existing social/medical conditions).  The Ontario public drug program began limiting SMBG supplies in August 2013.  This study was a cross-sectional, population-based, time series analysis evaluating patients with diabetes aged 19 or older who were eligible for public drug program between April 1, 2008-March 31, 2015. Patients were then stratified into four mutually exclusive groups based on therapy the year prior and test strip limitations were determined based on likelihood of hypoglycemia. Those who used insulin were allowed up to 3000 strips per year; those taking oral glycemic control agents known to cause hypoglycemia (e.g., sulfonylureas) were limited to 400 test strips annually, and those prescribed oral glycemic control agents that do not cause hypoglycemia (e.g., metformin, thiazolidinediones), or no medications were limited to 200 test strips annually.

The primary analysis was emergency department (ED) visits for hypoglycemia or hyperglycemia. The secondary outcome assessed A1C change. A sensitivity analysis was performed specifically for high volume users  — defined as those who used more than the annual limit of test strips in the year prior to implementation.  Given that very few insulin-treated patients exceeded the limit of 3000 annually, this group was excluded from the sensitivity analysis.

During the seven-year study, the number of eligible patients increased by 51% (N = 834, 309) – likely reflecting the increasing prevalence of type 2 diabetes in the population as well as increased enrollment in the Ontario drug program. Eligible patients were a mean of 72.3 years old and slightly more than half (50.4%) were male. Results were presented by age subgroups <65 years and >65 years.  A majority of patients were ≥65 years old (84.7%)

The implementation of SMBG test strips limits was associated with a nonsignificant reduction in ED visit rate for both hypoglycemia and hyperglycemia in both age groups (Table 1). When looking at the specific treatment groups, rates of hyperglycemia and hypoglycemia were highest among insulin-treated patients; however, outcomes remained stable over time in all four treatment groups. With regard to mean A1C, no change was observed after implementation of the quantity-limit policy and A1C values remained stable over the entire study period (ranging between 7.4% to 7.7% in those <65 years and 7.0% to 7.2%  in those ≥65 years, p=NS).

Table 1: ED visits over study period (2008-2015, policy limitation Aug 2013)

^{NS = non-significant}

In the sensitivity analysis of 140,118 high volume users, the rates of hypoglycemia, hyperglycemia, and A1C values were lower than the overall group.  However no change was seen after implementation of policy limits.

These results are consistent with recent evidence that failed to show a benefit from frequent SMBG (once daily vs ≥2 daily tests) in terms of improved glycemic (A1c) control.⁶ Moreover, glycemia-related ED visits were not significantly impacted when SMBG monitoring was less frequent.  A strength of this study is utilizing hard outcomes (ED visits for hypoglycemia and hyperglycemia) versus solely surrogate outcomes (e.g., A1C) which have routinely been the primary outcome in past studies. It provides evidence that patients can be safely managed on antihyperglycemic therapies that have a low risk of hypoglycemia without the need for routine glucose monitoring.

While the quality of care does not appear to have been negatively impacted, the SMBG test stip policy limitation led to significant cost savings — a 20% decrease the first year after introduction — from $107 million to $83 million dollars.⁵ These cost savings were primarily observed in non-insulin treated patients. Therefore, limiting SMBG can result in significant cost savings without increasing risk for patient harm.

There are several limitations to this study. First, it only assessed the impact for a period of 1.5 years after the policy implementation. However, one would expect any negative impact to be seen immediately after implementation of limits as this is when the change would have had the greatest impact on patient behaviors, especially among high volume users. Furthermore,  the study did not look at specific sub-populations such as newly diagnosed patients or patients with poorly controlled diabetes (A1c >9%).  Nor did the authors perform an analysis based on the type of insulin regimen (once daily basal insulin regimens versus multiple daily dosing regimens). Perhaps more frequent SMBG is beneficial in some subgroups of patients and may lead to improved glycemic control. Future studies are needed to determine whether SMBG limitations affect cardiovascular outcomes or microvascular complications long term.

As an observational claims-based time series study, the investigators could not assess how often clinicians made changes to therapy based on SMBG. SMBG is most useful when the blood glucose values influence changes to pharmacotherapy or lifestyle. There is an ongoing study of non-insulin treated patients with type 2 DM to determine the effect of SMBG with monthly follow-up visits on A1c levels.⁸  This study may provide further insight into the benefits of SMBG with close follow up.

As costs of healthcare continue to rise by nearly 5% every year,⁹ it is imperative to find ways to limit spending. Based on this study, limiting SMBG testing supplies while checking A1c levels every 3 to 6 months resulted in significant cost savings without causing patient harm. It may be time to reduce the frequency of home monitoring and focus more on appropriate in-office follow up for treatment modifications. Do you agree? Should we cut costs by limiting SMBG testing supplies in non-insulin treated patients? Is routine testing necessary? Let us know what you think.