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CI: Best Method to Estimate RMR (2010)

Citation:

Compher C, Cato R, Bader J, Kinosian B.  Harris-Benedict equations do not adequately predict energy requirements in elderly hospitalized African Americans.  J National Med Assoc 2004;96(2):209-214. 

PubMed ID: 14977280
 
Study Design:
Observational Cohort
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To compare measured RMR with Harris-Benedict predictions of BEE in a hospitalized elderly African-American cohort.
Inclusion Criteria:
African-American patients 65 years or older referred for nutritional consultation or for management of enteral of parenteral feedings.  A subset received measurement of energy expenditure by indirect calorimetry.  No diagnoses or nutritional states were excluded.
Exclusion Criteria:
  • Patients who had length of stay <3 days
  • Those requiring respiratory isolation
  • Those who were unable to cooperate with the test
  • Any measurements where steady state gas exchange conditions were not achieved and where inaccuracy of the energy expenditure measurement was likely
Description of Study Protocol:

Recruitment

All African American patients 65 years or older, admitted to the Skilled Nursing Facility or general medical floors of the University of Pennsylvania Health System/Presbyterian Medical Center during 1998.

Design

Observational Cohort.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured with indirect calorimetry and compared to estimations from equations.

Statistical Analysis

Descriptive statistics included mean, standard deviation, and percentages.  Pearson's correlation was used to compare RMR to BEE, height, weight and age for the entire cohort, and controlled for gender.  Differences in RMR and BEE for individual subjects were compared statistically by paired t-test.  Differences in RMR and BEE by gender were compared by ANOVA with post-hoc Scheffe test.  For all statistical evaluations, p < 0.05 was considered significant. 

Data Collection Summary:

Timing of Measurements

Each patient had RMR measured once and equations estimated.

Dependent Variables

  • RMR measured using indirect calorimetry with a Deltatrac, using a strict protocol, with patients at rest for at least 30 minutes in a thermoneutral environment and were silent.  Steady state measurement was defined as 5 consecutive 1-minute measures of VO2 and VCO2 with a coefficient of variation of <5%.  Inaccurate tests by RQ not accepted.  No discussion of calibration.
  • RMR estimated with Harris-Benedict equation, no adjustments 

Independent Variables

  • Demographic information collected by medical record review
  • Height, weight
  • Ventilated patients had not experienced a change in ventilator settings during or 30 minutes prior to the measurement
  • Patients had not received oral or bolus enteral feedings in the previous 4 hours
  • Continuous 24-hour enteral or parenteral feedings were not stopped for RMR tests 

Control Variables

  •  Gender
Description of Actual Data Sample:

Initial N: 61 subjects

Attrition (final N):  61 subjects, 21 men, 40 women

Age:  79.6 +/- 8.9 years, range 65 - 102 years

Ethnicity:  African-American

Other relevant demographics: 3/21 men and 2/40 women were receiving mechanical ventilation

Anthropometrics:  mean BMI 21.5 +/- 4.9.  Men BMI:  21.8 +/- 4.7, Women BMI:  21.3 +/- 5.1

Location:  Pennsylvania

 

Summary of Results:

Other Findings

Mean RMR for entire cohort was 1391.9 +/- 271.4 (range 914 - 2361 kcal/day).

RMR for 56 patients not requiring mechanical ventilation was 1369.8 +/- 267.4 kcal/day.

Mean Harris-Benedict BEE for entire cohort was 1149.7 +/- 183.1 kcal/day (range 841 - 1856 kcal/day) and 1146.6 +/- 187.6 kcal/day in nonventilated patients.

Measured RMR was significantly greater than predicted BEE (p = 0.001, t test).

Only 16/61 patients had RMR within 10% of the BEE, and only 2/61 patients had RMR <90% of Harris-Benedict BEE prediction.  74% of all measurements are >110% BEE. 

Caloric expenditure averaged 24.7 +/- 5 kcal/kg/day, but the range was broad (14 - 39 kcal/kg/day).

The BEE prediction was 20.3 +/- 2.4 kcal/kg/day.

Author Conclusion:
This study underscores the limitations of predictive equations in current use to estimate energy requirements in very elderly, ill, African-American patients.  Since no adequate estimate has been clinically validated in this population, and the actual range in energy needs is quite variable, the safest plan for longer-term nutrient prescription and for all patients with nutritional risk remains the measurement of energy expenditure. 
Funding Source:
Reviewer Comments:

Valid IC protocol but calibration not mentioned.  Statistical correlations not reported.  Authors note limitations of study include activity expenditure not accounted for.  Only a subset of the cohort received measurements.

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? Yes
  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? 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? ???
  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? 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? 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? ???
  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