EAL

DM: Blood Glucose Self-Monitoring (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate once- and twice-daily self-monitored blood glucose (SMBG) testing strategies compared with four-times daily testing is assessing glycemic control and detecting hypoglycemia or hyperglycemia in patients with stable insulin-treated type 2 diabetes.

Inclusion Criteria:

Type 2 diabetes diagnosed after age 35
Therapy with long-acting insulin
Mental competence
Stable glycemic control (no new oral agents, no insulin adjustments >10% in preceding 2 months)

Exclusion Criteria:

Not enrolled in primary care
History of diabetes ketoacidosis
Titrating insulin doses
Unable to test blood glucose regularily
Unlikely to survive 1 year
Abused alcohol or drugs
Chronic liver or pancreatic disease
Chronic infectious diseases
Endocrinopathies other than diabetes that affect glucose homeostasis
Immunocompromised states
Treatment with glucocorticoids
Using insulin pump

Description of Study Protocol:

Recruitment

Randomly selected potential subjects from pharmacy profiles
Medical records reviewed to determine eligibility
Contacted the primary doctor for approval to enter subject into study prior to consenting subject

Design: Prospective Cohort

Blinding used (if applicable)

Not applicable

Intervention (if applicable)

Subjects were observed performing SMBG and provided further training if necessary
Subjects were instructed to obtain SMBG prebreakfast, prelunch, predinner and bedtime everyday for 8 weeks
No treatment recommendations were given to subjects

Statistical Analysis

Mean and standard deviation SMBG was calculated for each individual testing time, for each combination of twice-daily testing, and for all four testing times combined
Subject's SMBG readings were excluded if 4 or more consecutive days were missed or if less than 7 days per week were tested
Bivariate linear regression was done to determine the correlation of mean SMBG or various times of the day and the A1C done at 8 weeks

Data Collection Summary:

Timing of Measurements

Baseline data collection: demographics, socioeconomic status, marital status, psychological profiles, diabetes complications and treatments, hypoglycemic medications, comorbidity, and barriers to care
SMBG meters were downloaded at 4 and 8 weeks
A1C was measured at 4 and 8 weeks

Dependent Variables

Independent Variables

SMBG

Control Variables

None discussed

Description of Actual Data Sample:

Initial N: 247 subjects enrolled

Attrition (final N): 212 subjects completed the monitoring period. 48 subjects were excluded for noncompliance and an additional 14 subjects whose follow-up A1C was not obtained within 4 days after end of montoring. Analysis based on 150 subjects (95% male)

Age: 65.6 ± 9.6 years

Ethnicity: 73% White; 15% Hispanic; 10% African-American; 2% Other

Other relevant demographics: Duration of diabetes 14.6 ± 9.5 years

Anthropometrics: Baseline A1C was 8.0 ± 1.8 %

Location: New Mexico, Arizona and Southern California

Summary of Results:

**Correlation of testing time mean glucose with A1C at week 8**
Testing time	Correlation coefficient	P value
Prebreakfast	0.67	<0.001
Prelunch	0.67	<0.001
Predinner	0.70	<0.001
Bedtime	0.65	<0.001
Prebreakfast/prelunch	0.73	<0.001
Prebreakfast/predinner	0.75	<0.001
Prebreakfast/bedtime	0.75	<0.001
Prelunch/predinner	0.74	<0.001
Prelunch/bedtime	0.74	<0.001
Predinner/bedtime	0.74	<0.001

Other Findings

The correlation coefficient between the mean glucose from all four testing times combined and the A1C at week 8 was 0.79 (P = 0.0001).
Mean A1C at week 8 was 7.48 ± 1.43 %.
At least one hypoglycemic reading was reported by 64% of the subjects, most occuring prelunch.
Most hyperglycemic readings occurred bedtime; second highest number of hyperglycemic readings occurred predinner.
Prelunch/predinner and Prelunch/Bedtime captured the most out-of-range readings.

Author Conclusion:

Rotating testing times explained more of the variance in A1C than any fixed once-daily testing strategy.

Funding Source:

Reviewer Comments:

The mean A1C changed > .5 % during the 8 week period.
Data from 61% of subjects originally enrolled was used in the analysis.

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
	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
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	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
	2.2.	Were criteria applied equally to all study groups?	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?	No
3.	Were study groups comparable?		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?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	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
4.	Was method of handling withdrawals described?		???
	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%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	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?		Yes
	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
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	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
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
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	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?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	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
	6.8.	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
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	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
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	N/A
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
	8.2.	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
	8.4.	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)?	N/A
	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
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes