Is Self-Monitoring of Blood Glucose Appropriate for All Type 2 Diabetic Patients? The Fremantle Diabetes Study

Davis W, Bruce D, Davis T. Diabetes Care. 2006;29:1764-1770.

The association between self-monitoring of blood glucose (SMBG) and glycemic benefit is relatively unclear. Although there is evidence linking intensive glycemic control with the reduction of chronic diabetes mellitus, the role of SMBG has not yet been validated due to adverse factors, such as the increasing burden it places on self-care and its contribution to rising health care costs. Thus, in order to gauge the functionality and efficacy of SMBG, the Fremantle Diabetes Study was conducted to assess the relationship between the use of SMBG, diabetes treatment, and glycemia in patients with type 2 diabetes.

This study included both cross-sectional and longitudinal analyses, and reported the status of 1817 community-based patients. The cross-sectional study of 1286 patients with type 2 diabetes prior to study onset was provided the percentage performing SMBG, frequency of SMBG use, the association between SMBG use and frequency of A1C assessment, and SMBG cost. The longitudinal observational analysis consisted of 531 patients who attended 6 annual assessments (baseline plus 5 reviews). This subgroup was also measured for the proportion using SMBG, SMBG frequency, glycemic control, and number of hypoglycemic episodes based on SMBG status. At each assessment, diabetes-related data were recorded in addition to information on medication, smoking and socioeconomic status, education and ethnicity, fluency in the English language, alcohol use, and exercise history. Two health status questionnaires, diabetes quality of life (DQOL) and the Rosser Index, were also applied. Following baseline evaluation, all patients were divided into 4 distinct groups based on frequency of SMBG testing; never (Group 1), <1 per week (Group 2), ≥1 per week and <1 per day (Group 3), and ≥1 per day (Group 4). Subjects were classified as adherent SMBG users if they were treated with oral hypoglycemic agents (OHAs) and/or insulin and performed SMBG one or more times a day, or if they controlled A1C levels through a strict diet and administered any SMBG.

Characteristics of the patients in the cross-sectional study were diabetes duration of 4 years, mean BMI of 29.6±5.5 kg/m², and median A1C of 7.4%, along with 32% of them receiving diet treatment, 56% receiving OHAs, and 12% treated with insulin with or without OHAs. Seventy percent of patients reported using SMBG with a median of 4 tests per week, and the 30% who refused to perform SMBG did so for a variety of reasons, including no education on how to perform SMBG, no motivation to start SMBG, fear of finger pricks, and physical or mental disability preventing its use. Additionally, all 66% of patients treated by diet control alone were adherent SMBG users, compared to 64% of the patients treated with insulin and 25% of the OHA-treated patients. Subjects more adherent to using SMBG were those who self-reported hypoglycemic events, were younger, had lower A1C, were insulin users, had a lower alcohol consumption, received diabetes education, visited diabetes-related outpatient clinics, and took insulin with or without OHAs (Groups 3 and 4). However, compared to less adherent users, these patients reported worse general health, including impairment in mobility and activity, decrease in self-care and social/personal relationships, and a decrement in positive feelings. No association was noted between fasting plasma glucose and SMBG or DQOL measures and SMBG. Additionally, there was no significant glycemic benefit associated with SMBG in any treatment group.

Compared to the 763 other patients at baseline, the subgroup of 531 who attended annual assessments were generally younger, more likely to be male, had a shorter diabetes duration, better glycemic control, fewer diabetic complications, and were less likely to have died prior to follow-up. Additionally, there was a notable increase over time in the proportion of people using SMBG, from 75.2% at baseline to 85.5% at the third assessment following baseline review. There was also a decrease in diabetes-treated patients from 34.8% at entry to 19.4% at the fifth assessment following baseline review; in contrast, OHA users increased from 57.5% to 64.9% and those using insulin with or without OHAs doubled from 7.8% to 15.7%. Similar to the cross-sectional group, the longitudinal cohort did not manifest any difference in A1C or FPG within treatment groups based on SMBG status. SMBG costs for diet and OHA-treated patients were similar, whereas the costs were lower for insulin-treated patients; projected annual costs for SMBG would be A$51 million (Australian) with an additional A$6 million (US $4,548,901) for glucometers.

Although the American Diabetes Association posits that SMBG should be performed 3 or more times per day for insulin-treated patients and supports low-level evidence of benefits to patients using once-daily insulin, OHAs, or diet alone, this study did not prove a positive association between SMBG testing or its frequency with glycemic benefit in patients with type 2 diabetes. The authors concluded that study limitations, including the lack of evaluation of SMBG delivery and application, as well as other independent variables, may explain this difference. Regardless of these factors, SMBG can be useful in the identification and prevention of hypoglycemia and dose adjustment.