EAL

COPD: Determination of Energy Needs (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To characterize the relationships between lung function, body composition, REE, serum leptin concentrations, and markers of inflammation in a group of weight-stable patients with clinically advanced emphysema.

Inclusion Criteria:

Individuals with severe emphysema who were weight stable, screened for advanced emphysema by pulmonary function tests and CT scanning of lungs
None had a >10% change in weight within the 6 months prior to enrollment

Exclusion Criteria:

Cases:

Smoked within 6 months of evaluation
Previously diagnosed pulmonary vascular disease, ischemic heart disease, or congestive heart failure
None were hospitalized during 6 months prior to inclusion
None had other illnesses known to affect either BMI, soluble tumor necrosis factor receptors, or leptin levels, such as infection, thyroid disease, cancer or collagen vascular disease
None had abnormalities in fluid balance manifested by congestive heart failure, ascites, or pleural effusion

Controls:

History of smoking, concomitant lung disease, or other serious medical illness

Description of Study Protocol:

Recruitment

Patients were participants of the National Emphysema Treatment Trial. Recruitment of healthy controls not described.

Design

Case-Control Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

Data were tested for normality using Kolmogorov-Smirnov test and groups compared using two sample t test. Univariate regression analysis and multiple backward stepwise regression analyses were performed. Least-square technique was used to obtain the line that best fit the data. Within-group analyses also examined for gender-related differences in leptin, BMI, fat mass percentage, and other characteristics.

Data Collection Summary:

Timing of Measurements

Measurements made in both cases and controls and compared.

Dependent Variables

Weight measured with beam scale
Pulmonary function tests included spirometry, lung volumes by plethysmography, and single-breath diffusing capacity for carbon monoxide
Body composition assessed by bioelectrical impedance
Serum leptin levels assessed with ELISA
Serum tumor necrosis factor receptors (s-TNF-Rs) assessed with radioimmunoassay
Resting oxygen consumption normalized to kg (RVO2/kg) and fat free mass (RVO2/FFM), measured using indirect calorimetry

Independent Variables

Severe emphysema

Control Variables

Description of Actual Data Sample:

Initial N: 79 patients with severe emphysema (43 men, 36 women), 20 age-matched healthy controls (10 women, 10 men)

Attrition (final N): 79 cases, 20 controls

Age: mean age cases: 68 +/- 5 years, controls: 66 +/- 6 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics: Patient group and healthy group had similar age, BMI and body composition.

Location: New York

Summary of Results:

Characteristic	Cases (n=79)	Controls (n=20)	P value
BMI	25.7 +/- 4.7	26.0 +/- 2.2	NS
FFM, kg	56.1 +/- 10.3	57.6 +/- 9.0	NS
Percent FM	21.8 +/- 5.7	20.1 +/- 3.9	NS
Leptin, ng/ml	14.4 +/- 11.5	11.5 +/- 6.5	NS
sTNF-R 55, ng/ml	1.7 +/- 0.5	1.4 +/- 0.5	0.02
sTNF-R 75, ng/ml	3.2 +/- 0.7	2.8 +/- 0.6	0.02
RVO2, ml	242.1 +/- 43.5	181.5 +/- 30.4	<0.001
RVO2/kg, ml/kg	3.34 +/- 0.67	2.52 +/- 0.24	<0.001
RVO2/FFM, ml/kg	4.29 +/- 0.75	3.16 +/- 0.35	<0.001

Other Findings

RVO2/kg, RVO2/FFM and sTNF-R levels were higher in patients compared to healthy subjects.

There were no differences in serum leptin levels between emphysematous and healthy subjects, and there was no correlation between leptin and s-TNF-R and RVO2/kg.

Furthermore, both groups had similar gender-related differences in FFM, percentage of body fat, and serum leptin levels.

Patients with lower BMI showed the greatest differences from control subjects in RVO2/kg.

Author Conclusion:

We conclude that in patients with weight-stable emphysema, RVO2 is increased when compared to normal control subjects. This is especially true in patients with BMI in the lower end of the studied range. Additionally, emphysema patients as a group have increased levels of sTNF-Rs, which may indicate ongoing inflammation. Leptin correlated with BMI and gender in both emphysematous and healthy subjects, but was different between the groups. Although systemic inflammation and elevated RVO2 are features of weight-stable emphysema patients, it is possible that any imbalance between RVO2 and energy supply could become great enough to lead to weight loss in this susceptible group.

Funding Source:

Reviewer Comments:

Recruitment of controls not described, controls not matched for gender, and groups not equally sized.

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)	N/A
	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)	N/A

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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
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
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	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.)	???
	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?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	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?		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?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	Yes
	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?	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
	6.6.	Were extra or unplanned treatments described?	N/A
	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?	N/A
	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)?	Yes
	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?	No
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