EAL

DM: Blood Glucose Self-Monitoring (2007)

Citation:

Martin S, Schneider B, Heinemann L, Lodwig V , Kurth HJ, Kolb H, Scherbaum WA, for the ROSSO Study Group. Self-monitoring of blood glucose in type 2 diabetes and long-term outcome: an epidemiological cohort study. Diabetologia 2006; 49: 271-278.

PubMed ID: 16362814

Study Design:

Epidemiolgical cohort study

Class:

B - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To document and obtain data from patients with type 2 diabetes, from time of diagnosis through a period of several years, regarding the use of self-monitoring blood glucose (SMBG) and the occurrence of diabetes-related morbidity and all-cause mortality.

Inclusion Criteria:

Initially diagnosed with type 2 diabetes between January 1, 1995 and December 31, 1999
Demographic, diabetes therapy, and SMBG information available at time of diagnosis and at least one subsequent year

Exclusion Criteria:

Diagnosed with diabetes type 2 prior to age 45

Description of Study Protocol:

Recruitment

Primary care physicians were contacted by phone
Patient information was collected from 192 physician practices (143 general practitioners, 49 internists)

Design

Retrospective, comparative, epidemiological cohort study
Parallel-group design
Statistical balancing of baseline differences between two cohorts

Blinding used (if applicable)

Not applicable

Intervention (if applicable)

Not applicable

Statistical Analysis

Differences between baseline and follow-up numerical data was assessed using two-sided t tests (p value less than 0.05 was considered statistically significant).
Differences between fatal and non-fatal endpoints were analysed with Fisher's exact test.
Unadjusted hazard ratios (HR) were calculated.
Survival analysis was performed based on Kaplan-Meier estimates.

Data Collection Summary:

Timing of Measurements

Data was collected from medical records from time of diagnosis to time of death or study end in 2003

Dependent Variables

Survival time defined as date of diagnosis to non-fatal or fatal endpoint
- Morbidity/Non-fatal endpoints: myocardial infarction, stroke, foot amputation, blindness, end-stage renal failure
- All-cause mortality/ fatal endpoints

Independent Variables

SMBG

Control Variables

Cox regression analysis Model 1 adjusted for baseline differences and Model 2 adjusted for non-disease potential confounders

Description of Actual Data Sample:

Initial N: 3,268 (1,609 males/1,659 females) met study inclusion/exclusion criteria

Attrition (final N): 3,268

Mean Age: 60.1 years for males and 64.6 years for females (62.4 ± 9.6 for all)

Ethnicity: German

Other relevant demographics:

Cohorts identified as SMBG group if SMBG was documented in the medical record for at least 1 year OR were identified as non-SMBG group.

Anthropometrics

No significant difference between the SMBG group and the non-SMBG group in baseline measures of body mass index, blood pressure, total cholesterol, LDL-cholesterol, and HDL-cholesterol.
SMBG group and non-SMBG group did differ significantly at baseline in age, fasting blood glucose, A1C, and triglycerides (see table). There was also a higher proportion of men in the SMBG group.

**Significantly different baseline characteristics between cohorts**
	SMBG group	Non-SMBG group	p value
Age (years)	60.5 ± 9.1	64.0 ± 9.7	<0.001
Fasting blood glucose(mmol/l)	10.05 ± 4.24	8.66 ± 3.25	<0.001
A1C (adjusted) %	8.1 ± 2.4	7.2 ± 1.7	<0.001
Triglycerides (mmol/l)	2.86 ± 2.54	2.45 ± 1.80	<0.001

Location: Germany

Summary of Results:

**Analysis of fatal and non-fatal endpoints at study end**
	Non-fatal endpoint	Kaplan-Meier survival analysis	Fatal endpoint	Kaplan-Meier survival analysis
All subjects n=3,268 Non-SMBG cohort n=1,789 SMBG cohort n=1,479	293 (9%) 186 (10.4%) 107 (7.2%) (p=0.002)	HR= 0.63 (SMBG/non-SMBG) 95% CI 0.50-0.80 p<0.001	120 (3.7%) 79 (4.6%) 41 (2.7%) (p=0.004)	HR= 0.52 (SMBG/non-SMBG) 95% CI 0.36-0.76 p<0.001
Non-insulin subjects n=2,515 Non-SMBG cohort n= 1,707 SMBG cohort n=808	231 (9.2%) 177 (10.4%) 54 (6.7%) (p=0.002)	HR= 0.60 (SMBG/non-SMBG) 95% CI 0.44-0.82 p<0.001	93 (3.7%) 71 of 1,649 (4.3%) 22 of 866 (2.5%) (p=0.026)	HR= 0.54 (SMBG/non-SMBG) 95% CI 0.33-0.87 p=0.010

Other Findings

Fasting blood glucose and A1C decreased in both cohorts during the 1st year after diagnosis and remained unchanged for the remainder of the study period. The fasting blood glucose and A1C remained higher in the SMBG group at study end compared to the non-SMBG group (p<0.001).
Cox regression analysis showed SMBG reduced HR for non-fatal endpoint by about 1/3 and and reduced HR for fatal endpoint by about 1/2. Similar findings were noted in the non-insulin subjects.
Microvascular endpoints occurred more in the SMBG group: incidence 2.5 vs 1.5%, p<0.03.

Author Conclusion:

SMBG is a marker for better clinical outcome. SMBG was associated with decreased diabetes-related morbidity and all-cause mortality in type 2 diabetes, and this association remained in a subgroup of patients who were not receiving insulin therapy.

Funding Source:

Reviewer Comments:

This study included subjects that used insulin. There was no reported data on frequency of SMBG. Groups were different at baseline.

The relative likelihood of experiencing a particular event; an HR of 0.5 indicates that one group has half the risk of the other group. Hazard ratio = 1.0 means rates are equal; differences are likely due to chance.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
	1.	Was the research question clearly stated?	Yes
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
	1.3.	Were the target population and setting specified?	Yes
	2.	Was the selection of study subjects/patients free from bias?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
	3.	Were study groups comparable?	???
3.	Were study groups comparable?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	No
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	No
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	???
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	???
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
	4.	Was method of handling withdrawals described?	N/A
4.	Was method of handling withdrawals described?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
	5.	Was blinding used to prevent introduction of bias?	N/A
5.	Was blinding used to prevent introduction of bias?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
	6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?	Yes
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	No
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
	7.	Were outcomes clearly defined and the measurements valid and reliable?	Yes
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
	8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	???
	8.6.	Was clinical significance as well as statistical significance reported?	???
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
	9.	Are conclusions supported by results with biases and limitations taken into consideration?	???
9.	Are conclusions supported by results with biases and limitations taken into consideration?		???
	9.1.	Is there a discussion of findings?	???
	9.1.	Is there a discussion of findings?	???
	9.2.	Are biases and study limitations identified and discussed?	???
	9.2.	Are biases and study limitations identified and discussed?	???
	10.	Is bias due to study's funding or sponsorship unlikely?	???
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	???
	10.2.	Was the study free from apparent conflict of interest?	???