EAL

DM: Blood Glucose Self-Monitoring (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of this study was to define the correlation between A1C values and the percentage of home blood glucose (HBG) measurements within given ranges in a pie chart in three age-groups of subjects with type 1 diabetes.

Inclusion Criteria:

All subjects were patients at the Barbara Davis Center for Childhood Diabetes, Denver, CO

Grouped according to age:

Group A: 5 -11 years
Group B: 12-16 years
Group C: 17-35 years

Type 1 diabetes mellitus for > 1 year
Had a One Touch blood glucose monitor
Did blood glucose monitoring at least 3 times/day

Exclusion Criteria:

Not specifically mentioned.

Description of Study Protocol:

Recruitment:

Methods not specified.

Design:

Cohort Study.

Blinding Used (if applicable):

Not applicable.

Intervention (if applicable):

According to study protocol, the following occurred during routine clinic visits:

Downloaded last 30 days of home blood glucose (HBG) values from the subject’s glucose monitor using the Intouch data management software.
A1C was measured at the same visit (normal range: 3.4% – 6.2% )
Target range blood glucose values were defined by physicians at the center according to age groups:
- A & B: 3.9-10 mmol/L (70-180 mg/dL)
- C: 3.9-8.3 mmol/L (70-150 mg/dL)
Based on target blood glucose ranges, all values from downloaded monitors were grouped according to below target range, within target range, or above target range.

Statistical analysis:

Student's t test and polynomial regression analysis using the Stat View 4.02 software package were used.

Data Collection Summary:

Timing of measurements:

No specific timing of home glucose testing was indicated.

Dependent variables:

Independent variables:

Average blood glucose/percentage of HBG measurements within given ranges

Control variables:

The same laboratory equipment was used to analyze all samples. Standards and controls were run routinely from the American College of Pathology and all were in range.

Description of Actual Data Sample:

Initial N, Final N, Age, Ethnicity and Other Relevant Demographics:

Age-group(years)	Subjects (n)	Caucasion (%)	African-American (%)	Hispanic-American (%)	Average blood glucose (mg/dl)(mean)	A1C %mean)*
5-11 (Group A)	233 (106 female, 127 male)	90 (n=209)	5 (n=12)	5 (n=12)	185	8.7
12-16 (Group B)	185 (97 female, 88 male)	94 (n=173)	3 (n=6)	3 (n=6)	188	8.8
17-35 (Group C)	168 (104 female, 64 male)	97 (n=163)	0.5 (n=1)	2 (n=4)	166	7.9

Anthropometrics:

*Group C had a significantly lower mean A1C value compared to groups A and B (P<0.001).

*44 subjects (26%) in group C were on the insulin pump; none in groups A and B were on the pump. Those on the insulin pump had a mean A1C of 7.7%, compared to 8% for those not on the pump.

Location: Barbara Davis Center for Childhood Diabetes, Denver, CO

Summary of Results:

Analysis of 7.0% A1C; Range of HBG needed to achieve respective target ranges*

	Average Blood Glucose	Within Target Range	Below Target Range	Above Target Range
5-11 year olds/ Group A	153 mg/dl	49%	18%	33%
12-16 year olds/ Group B	150 mg/dl	53%	17%	30%
17-35 year olds/ Group C	146 mg/dl	45%	18%	37%

* Target ranges per Group : A & B: 70-180 mg/dL; C: 70-150 mg/dL

Other Findings

Analysis of available longitudinal data, from 276 subjects, showed a strong correlation of the changes in A1C values to the changes in blood glucose values (P=0.01).

A strong correlation (p=0.001) was found between A1C values and the average blood glucose in all three groups. In all three groups, lower A1C values correlated strongly with the percentage of HBG values within and below target range, while higher A1C values correlated strongly with the percentage of HBG above target range (p<0.001).

The regression equation was used to predict the correlated A1C to the average BG and the percentage of HBG that were within, below and above the target range based on the known correlations. Any given A1C can be shown in a pie shaped graph displaying percentage of below, within, and above HBG.

Author Conclusion:

These data showed that a pie-shaped graph of the home blood glucose values can be useful as a clinical parameter in helping patients and families achieve desirable HbA1C values. Based on this research study, there now exists a model of how to evaluate HBG values and predict the corresponding A1C. All three age groups were similar in the ABG and corresponding A1C.

Funding Source:

Government:

Public Health Service Research Grant

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

This information could be used in treating/educating patients/families about the relationship between daily blood glucose and A1C and the percentage of blood glucose levels above target range. If half of the HBG measurements fall within a given target range, the corresponding A1C could be 7%. Both daily blood glucose and HbA1C measurements are needed to monitor glycemic control.

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?		???
	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?	No
	2.2.	Were criteria applied equally to all study groups?	???
	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?	Yes
3.	Were study groups comparable?		Yes
	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?	Yes
	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.)	Yes
	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
	4.1.	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
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	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
	5.1.	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?	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
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?	Yes
	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
	6.4.	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	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?	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
	8.1.	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?	Yes
	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?	N/A
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