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Hospitalized (Non-ICU) Adults (2010-2012)

Citation:

Glynn CC, Greene GW, Winkler MF, Albina JE.  Predictive versus measured energy expenditure using limits-of agreement analysis in hospitalized, obese patients.  JPEN 1999;23:147-154. 

PubMed ID: 10338222
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To examine methods used to determine energy expenditure in acutely ill, hospitalized patients with moderate to severe obesity, by comparing predictive formulae with indirect calorimetry measurements.
Inclusion Criteria:
Moderate to severe obesity by BMI of 30 or greater.
Exclusion Criteria:

Exclusion criteria included:

  • <21 years of age
  • Amputation
  • Outpatient studies
  • No available indirect calorimetry measurement
  • Deviation of >10% in indirect calorimetry parameters
  • Duplicated report
Description of Study Protocol:

Recruitment

Patients referred to the Nutritional Support Service of Rhode Island Hospital.

Design

Cross-Sectional Study. 

Blinding used (if applicable)

Not applicable. 

Intervention (if applicable)

RMR measured with indirect calorimetry and estimated with equations.

Statistical Analysis

Descriptive statistical analysis of BMI for the population presenting for nutritional support was performed.  Pearson product-moment correlations determined the strength of the relationship between methods for ideal weight determination and the predictive formulae and MREE.  Limits of agreement analysis determined bias (the mean difference between measured and predicted values) and precision (the standard deviation of the bias).  Predictive accuracy was determined within +/-10% of MREE.  Sample was stratified to determine if inherent differences existed between levels of obesity.  A series of univariate ANOVAs were conducted with the bias, using formulae as dependent variables and levels of obesity as independent variables.  Post-hoc analyses used Tukey's studentized range test.  Chi-square tests determined if selected variables were also associated with an estimation error >10% for the formulae:  age > 65 years, trauma, ventilator dependence, fed state, cancer, and complications incurred during hospital course.  t tests or ANOVA determined the relationship between these variables and formulae bias.

Data Collection Summary:

Timing of Measurements

Retrospective review of indirect calorimetry measurements and information for equations.

Dependent Variables

  • RMR measured through indirect calorimetry with a Deltatrac Metabolic Monitor according to Rhode Island Hospital Respiratory Care Department Protocol by Registered Respiratory Therapists (calibration performed daily, studies ran 12 - 15 minutes, steady state not mentioned)
  • RMR estimated using variations of Harris-Benedict using ideal, adjusted weights of 25% and 50% and actual weights with stress factors ranging from 1.0 to 1.5
  • Hawmi method compared with 1959 Metropolitan Life Tables to determine ideal weight 
  • RMR estimated using Ireton-Jones equations for hospitalized patients
  • RMR estimated using the ratio of 21 kcal/kg actual weight

Independent Variables

  • Nutritional support service provided working records maaintained during course of nutritional support, providing indication for nutritional support, feeding modality, average energy intake, nutrient composition, fasting (88% were in a fed state, specifics not mentioned)
  • Complications, principal operations and procedures noted in chart
  • Applicable comments of respiratory therapist noted in chart
  • Level of obesity
  • Trauma
  • Ventilator dependence
  • Cancer

Control Variables

  • Age

 

Description of Actual Data Sample:

Initial N: 726 patients.  85 were identified with a BMI of 30 or greater.  61 subjects remained after 24 were excluded based on exclusion criteria.

Attrition (final N):  57 patients with BMI of 30 - 50, 32 spontaneous breathing, 25 ventilator dependent (31 women, 26 men).  4 excluded for having BMI > 50.

Age:  Mean age 54 years. 

Ethnicity:  Not mentioned

Other relevant demographics:  Not mentioned

Anthropometrics:  A significant effect of obesity on bias was found.  40 subjects had BMI between 30 - 35, 9 had BMI between 35 - 40, 7 had BMI between 40 and 50.  4 excluded subjects had BMI > 50. 

Location:  Rhode Island

 

Summary of Results:

 

All Patients

Harris-Benedict avg Ireton-Jones 21 kcal/kg

r

0.85, p = 0.001 0.83, p = 0.001 0.64, p = 0.001

Bias

182

233

267

Precision 123 177 203

+/- 10% MREE

67%

49%

24%

 

Spontaneous Breathing

Harris-Benedict avg Ireton-Jones 21 kcal/kg

n

32 32 32

Bias

159

248

236

Precision 112 198 166

+/- 10% MREE

69%

56%

41%

Ventilator Dependent

Harris-Benedict avg Ireton-Jones 21 kcal/kg

n

25 25 25

Bias

210

243

307 

Precision 248 149 239

+/- 10% MREE

64% 

40%

44%

Other Findings

Range of indirect calorimetry measurements was 1340 - 3310 kcals (mean 2036 +/- 414).  The mean kcal/kg of actual weight was 14 - 31 (mean 21 +/- 3 kcal/kg).

Harris-Benedict equation using average of ideal and actual weight adjusted with stress factor of 1.3 best predicted MREE and was selected to represent the Harris-Benedict equation in analyses.

The adjusted Harris-Benedict average weight equation was optimal for predicting MREE for the total sample (bias = 182 +/- 123; 67% +/- 10% MREE) as well as the spontaneous breathing subset (bias = 159 +/- 112; 69% +/- 10% MREE) and ventilator dependent subset (bias = 210 +/- 248; 64% +/- 10% MREE).

No effect was found for age > 65 years, incidence of trauma, complications, fed state, or cancer diagnosis on the bias of predictive formulae.  Ventilatory status was found to be statistically significant for the Ireton-Jones obesity equation (t = 2.6, p < 0.05).  None of the variables were significant predictors of whether the applied formulae would fall within +/- 10% MREE.

Author Conclusion:
The Harris-Benedict equation, which uses the average of ideal and actual weight and a stress factor of 1.3, best predicted MREE in acutely ill, obese patients with BMIs of 30 - 50.  The mean MREE was 21 kcal/kg actual weight.  Though not an accurate predictive formula in itself, the ratio may be useful in evaluating values obtained from predictive formulae.  The absolute value should be used in limits of agreement analysis.  Predictive formulae were least accurate for obese (BMI > 50) and ventilator dependent patients; therefore, indirect calorimetry is recommended until future studies validate the accuracy of predictive formulae for these patients.
Funding Source:
University/Hospital: University of Rhode Island, Rhode Island Hospital, Brown University
Reviewer Comments:
IC only 12 - 15 minutes, steady state not mentioned.  88% in fed state, not sure if feedings started more than 24 hours earlier.
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? 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? 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? 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? 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? Yes
  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? 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? N/A
  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? ???
  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? ???
  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? 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
  8.6. 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? 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