OBJECTIVE -We sought to assess longitudinal association between self-monitoring of blood glucose (SMBG) and glycemic control in diabetic patients from an integrated health plan (Kaiser Permanente Northern California).RESEARCH DESIGN AND METHODS -Longitudinal analyses of glycemic control among 1) 16,091 patients initiating SMBG (new-user cohort) and 2) 15,347 ongoing users of SMBG (prevalent-user cohort). SMBG frequency was based on pharmacy use (number of blood glucose test strips dispensed), and glycemic control was based on HbA 1c (A1C). In the new-user cohort, ANCOVA models (pre-and posttest design) were used to assess the effect of initiating SMBG. In the prevalent-user cohort, repeated-measure, mixed-effects models with randomintercept and time-dependent covariates were used to assess changes in SMBG and A1C. All models were stratified by therapy (no medications, oral agents only, or insulin) and adjusted for baseline A1C, sociodemographics, insulin injection frequency, comorbidity index, medication adherence, smoking status, health care use, and provider specialty.RESULTS -Greater SMBG practice frequency among new users was associated with a graded decrease in A1C (relative to nonusers) regardless of diabetes therapy (P Ͻ 0.0001). Changes in SMBG frequency among prevalent users were associated with an inverse graded change in A1C only among pharmacologically treated patients (P Ͻ 0.0001).CONCLUSIONS -These observational findings are consistent with short-term benefits of initiating SMBG practice for all patients but continuing benefits only for pharmacologically treated patients. Differences in effectiveness between new versus prevalent users of SMBG have implications for guideline development and interpretation of observational outcomes data. (2) and dissemination of the Self-Monitoring of Blood Glucose Consensus Conference (1986) have contributed to an increased attention to tight glycemic control in patients with diabetes and a concomitant promotion of self-monitoring of blood glucose (SMBG). However, SMBG is costly for patients and health insurers, and the clinical value of this practice for patients who are not treated by insulin remains controversial. Because of inconsistent evidence, current recommendations vary widely and are typically vague (3). For example, an American Diabetes Association's 2005 position statement states, "The optimal frequency and timing of SMBG for patients with type 2 diabetes on oral agent therapy is not known but should be sufficient to facilitate reaching glucose goals" (4). The high cost of test strips in an era of evidence-based medicine has created a demand for rigorous evaluation of the effectiveness of SMBG.
Diabetes CareNo studies, either experimental or observational, have addressed the longterm impact of various SMBG testing frequencies on glycemic control. In this article, we present results of the first longitudinal study of the association between SMBG frequency and glycemic control in diabetic members of a prepaid, integrated health plan. Additionally, special...