Glycemic self-monitoring and insurance coverage

A growing body of research is calling attention to significant rates of medication underuse and to adverse health consequences associated with high out-of-pocket drug costs, especially among patients with low incomes, multiple chronic illnesses or no prescription drug coverage.1^,2 Studies in the United States and Canada have shown that public- and private-sector policies limiting drug coverage lead to fewer prescriptions being filled,3^,4 higher rates of nursing home admissions5 and increased use of acute care services.3 Yet physicians often fail to identify patients who are burdened by high out-of-pocket expenses.6 Many patients with chronic illnesses who report having underused medications because of cost never discuss this underuse with their physicians.7^,8

In this issue Samantha Bowker and colleagues9 (see page 39) contribute to this body of research and expand the policy debate on the scope of health insurance coverage into the realm of medical supplies. They examine cross-sectional baseline survey and laboratory data from 405 non-insulin-using patients with type 2 diabetes who are enrolled in a randomized controlled trial designed to assess the effect of providing free blood glucose testing supplies on glycemic control. Of these patients, 41% had at least some level of insurance coverage for blood glucose testing supplies. In multivariate analyses adjusted for age, income, education, frequency of monitoring and perceived barriers to monitoring, they found that patients with insurance coverage of testing supplies had hemoglobin A_1c values that were 0.5% higher than the values for patients without such insurance coverage (p = 0.006). As the authors note, this finding is clinically significant. There were even larger differences among people with poorer baseline glycemic control (hemoglobin A_1c concentrations > 8.4%). These findings reinforce those of Soumerai and coauthors,10 who examined trends in hemoglobin A_1c concentrations 2 years before and after a large US health maintenance organization instituted coverage of blood glucose testing supplies. In that study, among the 288 patients who initiated self-monitoring of blood glucose, mean hemoglobin A_1c concentrations fell from 10.8% to 8.6%.

If the current study's findings are confirmed by subsequent results from the authors' randomized controlled trial, they will have important implications for the ongoing policy debate in Canada. Approximately 6% of Canadians have diabetes, and the prevalence of the disease is projected to increase by 35% over the next 25 years.11 The total economic burden of diabetes in Canada is estimated to exceed US$5 billion a year.11 Policy decisions determining which medications, procedures or supplies to cover should be based on sound scientific evidence of clinical benefit. Certainly, blood glucose testing supplies are expensive. However, for conditions such as diabetes whose associated morbidity and mortality are high, the greater the clinical benefit, the less significant are the costs of coverage relative to the downstream costs of treating complications of the disease.

Although Bowker and colleagues' findings are provocative, they must be considered in the context of the mixed findings of earlier research on self-monitoring among patients with type 2 diabetes who do not take insulin.12 In the face of limited empirical evidence, proponents argue that self-monitoring is an effective tool to guide patients and physicians in modifying diabetes management (including diet, physical activity and medication). Indeed, studies that have shown improved glycemic control with self-monitoring — even among patients taking insulin — have tended to be those in which self-monitoring was directly linked to concrete steps (such as titrating insulin doses) that patients could take in response to those values.12^,13 Few trials have examined the influence of self-monitoring on other modifiable behaviours such as diet and exercise.12 Yet self-monitoring appears most likely to play a significant role in improving glycemic control when it is an integral part of broader efforts to support diabetes self-management.

What, then, might be the mechanism for this study's observed effect of insurance coverage for self-monitoring supplies on glycemic control? Certainly, as the authors hypothesize, it could simply be the removal of a financial obstacle. One might then anticipate that those without coverage, who indeed were more likely to report cost as a barrier to self-monitoring, might also report a lower frequency of testing. However, frequency of self-monitoring did not appear to be independently associated with glycemic control. It is also possible that having insurance coverage — especially if patients had to choose to purchase private coverage on their own or proactively apply for supplemental coverage — is a marker for increased concern about health and involvement in diabetes self-care.

This study alerts us to an association between insurance coverage for blood glucose testing supplies and glycemic control. As Bowker and colleagues note, their randomized controlled trial of free self-monitoring supplies versus “usual health care policy” will more definitively establish the effect of covering these supplies and reduce concerns that other unmeasured attributes might account for the observed differences between the study groups.

This study reinforces several crucial messages for physicians. As with other possible obstacles to effective diabetes self-management, we must discuss with our patients the financial barriers they may be facing. More broadly, we must explore with patients the entire range of factors that they weigh when choosing whether and how to take prescribed medications or to engage in other diabetes self-care activities. Translating effective diabetes treatment regimens into improved clinical outcomes depends on patients' capacity and motivation to initiate and sustain those regimens.

𝛃 See related article page 39