CI: Best Method to Estimate RMR (2010)

Citation:
Ireton-Jones C, Jones JD.  Improved equations for predicting energy expenditure in patients:  the Ireton-Jones equations.  Nutr Clin Pract 2002;17(1):29-31. PubMed ID: 16214963
 
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 further evaluate the original data from the development of the Ireton-Jones equations to determine if their precision could be enhanced and to compare the Harris-Benedict equations with measured energy expenditure to determine if a statistically significant correlation could be obtained.
Inclusion Criteria:
Ventilator-dependent and spontaneously breathing patients hospitalized in an acute care setting.  Patients stratified according to diagnosis:  burn, trauma or other (diabetes, pancreatitis, cancer).
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Not specified in this article.

Design

Cross-sectional study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured with indirect calorimetry and estimated with equations.

Statistical Analysis

Multivariate regression analysis was used to correlate easily measurable patient data with measured energy expenditure using indirect calorimetry.  The 3 measures used to compare the previous equations and revised equations were the correlation coefficient between the equations and MEE, the mean of the prediction error between the equations and MEE, and the number of patients with MEE > the IJ equations vs number with MEE < IJ equations.  A comparative analysis was also made for the entire 300-patient population between Ireton-Jones and Harris-Benedict equations using actual body weight and total kcal/kg.

Data Collection Summary:

Timing of Measurements

RMR measured with indirect calorimetry and estimated using equations.

Dependent Variables

  • RMR measured with indirect calorimetry, details not provided
  • RMR estimated using Ireton-Jones equations
  • RMR estimated using Harris-Benedict equations, multiplied by factor of 1.3

Independent Variables

  • Height, weight
  • Gender
  • Age
  • Diagnosis
  • Ventilatory status
  • Obesity

Control Variables

 

Description of Actual Data Sample:

Initial N: original equations developed using 200 patients, validated using second group of 100 patients

Attrition (final N):  300 patients from both groups

Age:  not mentioned

Ethnicity:  not mentioned

Other relevant demographics:  99 total ventilator dependent

Anthropometrics:

Location:  Texas

 

Summary of Results:

 

  r Value Mean prediction error (kcal/day) % of patients with MEE above predicted

Original IJEE(v)

0.58 -271

 35%

Revised IJEE (v)

0.58

8

 48%

IJEE (actual body wt)

0.69

-6

 48%

HBEE (actual body wt) 0.60 410  76%
HBEE x 1.3 (actual wt) 0.60 -51  41%
21 kcal/day 0.46 503  81%

Other Findings

Statistical analysis of the spontaneously breathing patients showed no improvement in predictability of energy expenditure, therefore, no change was made to this equation.

The statistical analysis for the ventilator-dependent patients demonstrated that the equations could be improved to minimize the error by adjusting numerical values in the equation.

The mean prediction error of the original equation was -271 kcal/day, while the revised equation showed a mean prediction error of 8 kcal/day, while still maintaining the strong correlation.

The Harris-Benedict equation, multiplied by 1.3, hads a reasonable correlation but consistently predicted energy expenditure lower than the MEE.

For obese patients, the Ireton-Jones equations with actual body weight was significantly correlated with MEE (r = 0.67) and the mean prediction error was -96 kcal/day.

Harris-Benedict x 1.3 calculated with actual body weight for obese patients significantly correlated to MEE (r = 0.64), but the mean prediction error was -177 kcal/day.

Author Conclusion:
The Ireton-Jones equations for both spontaneously breathing patients and the revised equation for ventilator-dependent patients minimize the error in predicting energy expenditure for both obese and nonobese patients.  For all patients, including obese patients, the high r value indicates low variability from the MEE, and the corresponding mean prediction error shows that this predictive equation will be closest to the actual MEE.
Funding Source:
University/Hospital: Coram Healthcare
Reviewer Comments:
Many details left out of this paper as the article primarily served as a reanalysis of the data from the 1992 study.
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? 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) Yes
  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.) ???
  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.) ???
  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? ???
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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? 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? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  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? ???
  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? ???
  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? 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