The Cost of Self-Monitoring of Blood Glucose Is an Important Factor Limiting Glycemic Control in Diabetic Patients Free

Maintenance of near normoglycemia can delay or prevent microvascular complications, but it cannot be carried out without a program of patient education, including self-monitoring of blood glucose (SMBG) (1,2). Motivation toward SMBG depends on several ill-defined factors, and there is no consensus on the effectiveness of SMBG in diabetes management (3–6).

We undertook a single-blinded, control-matched, longitudinal study of patients with insulin-requiring diabetes (n = 62) to examine barriers to SMBG and determine whether eliminating the cost barrier would increase SMBG frequency and glycemic control. Eligibility criteria were insulin treatment with at least two injections/day for at least 1 year (1), HbA_1c >120% of upper limit of normal (2), and recent diabetes education (3). The patients completed questionnaires reporting their habitual SMBG frequency, perceived barriers to SMBG, monthly income, and any private health insurance plans to verify coverage for glucometer reagents. They were randomly assigned in a patient-blinded fashion to two groups of 31 patients each, matched for age, sex, education, income, private health insurance coverage, diabetes type, diabetes duration, number of years on insulin, habitual SMBG frequency, random blood glucose, HbA_1c, and number of daily insulin injections. They were asked to participate in the study over a period of 12 months, with second monthly visits to the research nurse, and they were instructed in the use of the glucometer DEX (Bayer, Etobicoke, Canada), but they were not given any information on how frequently they should self-monitor. A glucometer and 50 strips were supplied to one group of patients (control or C group), who were instructed to purchase additional strips as needed. A glucometer and 100 strips/month were given to the second group (no-cost or NC group). At each visit, random blood glucose and HbA_1c were measured, familiarity with the glucometer was checked, and the glucometer memory was downloaded using a computer software program (WinGlucofacts; Bayer, Elkhart, IN). No feedback was provided to the patient. Because of the small number of patients and the similar representation of diabetes types in both groups, the data were combined for statistical analysis.

At entry, patients indicated that they were not self-monitoring more often because testing was not convenient (47%), strips were too expensive (31%), they could feel their own blood glucose without testing (21%), testing was too painful (14%), or testing did not help (10%). Totals of 16 and 25 patients in the C and NC groups, respectively, completed the study (dropout rates of 48 and 19%, respectively). At the end of the study, the remaining patients indicated that testing was not convenient (29%), they could feel their own blood glucose without testing (20%), testing was too painful (17%), strips were too expensive (10%), or testing did not help (7%). The stated reasons were not significantly different between groups.

Glucometer-recorded SMBG frequency increased with time and was higher in the NC than in the C group (2.0 ± 0.2 vs. 1.4 ± 0.1 during the first 4 months, P < 0.05). Insulin dose increased ∼1.5-fold in the C group (58.5 ± 6.9 to 75.1 ± 12.1 unit/day, P < 0.05) but not in the NC group (52.5 ± 3.0 to 52.6 ± 3.4 units/day). HbA_1c initially decreased in both groups and then increased in the C group, and final HbA_1c was lower in the NC than in the C group (8.7 ± 0.3 vs. 9.9 ± 1.1%, P < 0.01). Average blood glucose at the end of the study was also lower in the NC than in the C group (205.2 ± 10.6 vs. 252.0 ± 39.6 mg/dl, P < 0.05).

Thus, although inconvenience was the main reported barrier to SMBG, cost was an important factor, perhaps explaining the higher dropout rate in the C than in the NC group. The simple strategy of supplying free strips increased compliance with SMBG and enhanced diabetes self-management. Overall, patients who were given free strips had lower HbA_1c and average blood glucose and insulin doses versus control subjects.