PubMed Health. A service of the National Library of Medicine, National Institutes of Health.

Shekelle P, Munjas B, Romanova M, et al. Self-Monitoring of Blood Glucose in Patients with Type 2 Diabetes Mellitus: Meta Analysis of Effectiveness [Internet]. Washington (DC): Department of Veterans Affairs (US); 2007 Sep.

SUMMARY AND DISCUSSION

In this chapter, we describe the limitations of our review and meta-analysis and then present our conclusions. We also discuss the implications of our findings for future research.

Limitations

Publication Bias

Our literature search procedures were extensive and included all articles identified in prior reviews plus additional articles. Our formal tests for publication bias did not indicate the presence of possible publication bias but such tests do not exclude the possibility that such bias exists. Therefore, readers are cautioned about this possibility.

Study Quality

An important limitation common to systematic reviews is the quality of the original studies. Recent attempts to define elements of study design and execution that are related to bias have shown that in many cases, such efforts are not reproducible and do not distinguish study results based on bias. Therefore, the current approach is to avoid rejecting studies or using quality criteria to adjust the meta-analysis results. We did use the Delphi list10 as a descriptive measure of quality. As there is a lack of empirical evidence regarding study characteristics and their relationship to bias, we did not attempt to use other criteria. Other aspects of the design and execution of a trial may be related to bias, but we do not yet have good measures of these elements. The sensitivity analysis of our main result did not yield any suggestion that the quality of the trials influenced our findings in a significant way.

Heterogeneity

While there were some differences in the population being assessed and the number of times and timing of SMBG recommended, the most important heterogeneity in this review was the differing intervention components added to SMBG and the difference in the recommendations for frequency of SMBG testing, provider interaction or algorithm to adjust medications, and intensity of education. While the statistical test for heterogeneity was not significant for six months and 12 month outcomes, this test has low power and does not preclude substantial heterogeneity among studies. There were too few studies to be able to support meta-regression to assess the relative effectiveness of these differences.

Applicability of Findings

Green & Glasgow40 provide a framework for evaluating the relevance, generalization, and applicability of research. Their framework includes assessing the participation rate, the intended target population, the representativeness of the setting, the representativeness of the individuals, and evaluating information about implementation and assessment of outcomes. As these data are rarely reported in the studies we reviewed, conclusions about applicability are necessarily weak. Furthermore, none of the trials assessed VA patients or VA core delivery systems. The observational studies done in VA did not report results compatible with SMBG being an effective intervention; however RCTs are generally preferred to observational studies when making estimates of efficacy and effectiveness.

Conclusions

With the above limitations in mind, we reached the conclusions displayed below.

KEY QUESTION #1: Is regular SMBG effective in achieving target A1c levels for patients with type 2 diabetes?

Studies of Efficacy

Achieving Target A1c Levels

There is little evidence to draw a conclusion about the effect of SMBG at achieving target A1c levels. We judged the strength of this evidence as very low. [GRADE: Very Low = Any estimate of effect is very uncertain.]

Improving Glycemic Control

We found that adding SMBG along with education, counseling, (and some times other components) results in a statistically significant decrease in A1c level of an absolute 0.21% at six months. Results at three months and one year are more variable, although there is a suggestion that this benefit may continue out to at least one year.

We judged the strength of evidence for this outcome as moderate, because individual trials did not in general report significant results and interventions were heterogeneous. [GRADE: Moderate= Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.]

Studies of Effectiveness in Veterans

Five observational studies of SMBG effectiveness in Veteran populations did not report statistically significant improvements in glycemic control. The results of the studies with Veterans do not negate the evidence from RCTs that the addition of SMBG and education can result in a decrease in A1c levels of about 0.3% absolute at six months and up to one year. However, these studies do raise the question of whether veteran patients are receiving the full possible benefits of SMBG. [GRADE: Very Low = Any estimate of effect is very uncertain.]

KEY QUESTION #2: Is regular SMBG effective in maintaining target A1c levels for patients with type 2 diabetes?

We did not identify any trials that directly assessed this question. Therefore, we draw no conclusion. [GRADE: Very Low = Any estimate of effect is very uncertain.]

KEY QUESTION #3: Does regular SMBG reduce the frequency of hypoglycemia in patients with type 2 diabetes?

The limited evidence available indicates that SMBG increases the frequency of recognized hypoglycemia. This is due to an increase in asymptomatic low blood sugar readings, and also an increase in mild-to-moderate symptomatic episodes. There is scant evidence about the effect of SMBG on more clinically significant hypoglycemia. We judge the strength of evidence for SMBG increasing asymptomatic and mildly symptomatic hypoglycemia as moderate. [Moderate = Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.]

KEY QUESTION #4: Is there evidence that different frequencies of testing result in differences in improvements in A1c?

We used meta-regression to assess the effect of the reported frequency of SMBG use in the RCTs (measures as times/week) on differences in A1c level compared to control. No association was found (p=0.99). Therefore we draw no conclusion about the effect of frequency of SMBG monitoring on A1c values, and judge the strength of the evidence to be very low. [GRADE: Very Low = Any estimate of effect is very uncertain.]

Cover of Self-Monitoring of Blood Glucose in Patients with Type 2 Diabetes Mellitus
Self-Monitoring of Blood Glucose in Patients with Type 2 Diabetes Mellitus: Meta Analysis of Effectiveness [Internet].
Shekelle P, Munjas B, Romanova M, et al.
Washington (DC): Department of Veterans Affairs (US); 2007 Sep.

PubMed Health Blog...

read all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...