Additional Information (Author responses to reviewer questions) about this clinical study is provided following the abstract below.

Transcription

1 Additional Information (Author responses to reviewer questions) about this clinical study is provided following the abstract below. Comparison of measured resting energy expenditure (mree) from a metabolic cart to a portable handheld device in maintenance hemodialysis patients: a feasibility study. Mariam S. Alavi, MS RD Renal Dietitian; This study was completed as part of the master s thesis requirement for the Master of Science in Clinical Nutrition Program at Rutgers - School of Health Related Professions Mariam.s.alavi@gmail.com Emily Peters, MPH Adjunct Instructor and Study Coordinator Department of Nutritional Sciences School of Health Related Professions Petersen@shrp.rutgers.edu Andrea Marcus, PhD, MPH Assistant Professor, Department of Nutritional Sciences School of Health Related Professions marcusab@shrp.rutgers.ed Diane Rigassio Radler, PhD, RD Associate Professor, Department of Nutritional Sciences; Director, Institute for Nutrition Interventions; School of Health Related Professions rigassdl@shrp.rutgers.edu Laura Byham-Gray, PhD, RD Professor and Director Master of Science in Clinical Nutrition Program Department of Nutritional Sciences laura.byham-gray@shrp.rutgers.edu

2 Abstract Background: A portable handheld device for measuring resting energy expenditure (REE) of patients on maintenance hemodialysis (MHD) compared to traditional indirect calorimetry may be a convenient, reliable estimation of the individual s energy needs. Objective: The purpose of this study was to determine the level of agreement in REE as measured by a metabolic cart and a portable handheld device among patients on MHD. Design: Prospective, descriptive, cross-sectional, pilot study. Participants: This study involved medically stable, English speaking patients receiving treatment at a single dialysis center in New Jersey. Measured REE (mree) from both devices was completed in 16 participants (94.1%). Statistical Analysis: The level of agreement between the mree from the portable handheld device compared to metabolic cart was analyzed using paired-samples t-tests and Bland Altman analysis. Statistical significance was p<0.05. Individual mree measurements were considered to be in agreement if the difference between the two measures was within ±10% of the mean or kcal. Results: The mean age of participants in the study was 60.6 ± 10.2 years and 70.6% were male. The mean BMI was 30.0 ± 7.1 kg/m 2. Most common etiology of CKD was hypertension (41.2%). There was agreement between the mree from the portable device when compared to the metabolic cart with 68.8% of measurements falling within the band of acceptability. All of the patients who fell outside the band of acceptability were overweight or obese. There was no statistically significant difference in the mean scores of the mree from the two devices (p=0.759). The majority of participants (94.1%) found the procedures for obtaining mree from the portable handheld device to be comfortable.

3 Conclusions: In this sample of patients receiving MHD, there was agreement between the mree from the two devices. The portable handheld device may be a reasonable option for clinicians to use in the assessment of energy requirements for patients on MHD as it was acceptable to participants. Further research is needed to evaluate the accuracy of the portable device for measuring REE in this population. Author/s responses to reviewer questions about manuscript submission: 1. Does author wish to use P<1.0? per measures within 10% for the mean? Also, in results, achieved p=0.759, over the p=0.05 confidence level. The α-level was calculated a-priori; as a result, we are unable to change the level at this time as data has already been collected. The reviewer is correct in stating that the paired-samples t-test comparing the mean REE (mree) from both devices was p= This indicates that the there was no statistically significant difference between the mree obtained from the metabolic cart compared to the mree from the portable handheld device. Therefore, the result of this study indicated that there was some level of agreement between the mree values from the two devices.

4 2. Does author wish to include values used for activity/stress factors? Thank you for your suggestion. Due to the many existing activity factors that could be used when calculating energy needs, we did not propose or recommend any specific activity or stress factors for use in the hemodialysis population. 3. Did study address any effect on Med Gem results when taking measurements after the participants were out of bed? I think some of the original literature supported it s use and sensitivity when measured before participants engaged in any ADLs or activity? Yes, that is correct. The MedGem is more sensitive when participants have not engaged in any activities. As described in the Study Methods and Procedures participants were instructed to adhere to resting energy conditions as closely as possible. However, due to the mechanics of the MedGem results, participants are recommended to sit upright and hold the device in order to obtain results. For this reason, the MedGem may not be as a precise in its estimations of REE compared to the indirect calorimeter. On the other hand, metabolic cart measurements were taken while the patient was reclining. For the sake of continuity and the comfort of the participant, we allowed the participants to recline during both measurements.

5 4. Please clarify the following sentence At the end of the test, the device produced an estimated RQ using only oxygen consumption data for calculating the mree values. Thank you for your question. The MedGem automatically sets the respiratory quotient (RQ) to a value of 0.85, a measure that is considered equivalent to a typical Western diet, because it is unable to measure carbon dioxide. For more information, please refer to the manufacturer s (Microlife Medical Home Solutions) website 5. It is a little unclear what position the patients were in during measurement with each device. If they were in a different position, was there a reason for these differing body positions? We thank the reviewer for this question. Please refer to the response to question #5 above. We also clarified the position the patients were in during each measurement by correcting line # Please describe how this analysis was performed The participants were stratified by age, BMI, dialysis vintage time, ethnicity, etiology of CKD, gender and race to attempt to further characterize the individuals that did not fall within the band of acceptability. No commonalities or patterns emerged. Thank you for your question. We examined the results from each variable to determine if there were any commonalities. Due to the small sample size, we did not conduct any

6 sophisticated analyses to determine if there were significant differences/commonalities observed. This may be an opportunity for further exploration in a larger sample. 7. What statistics were used for this statement: Women had higher mean mree when measured by the metabolic cart in comparison to men. Conversely, women had lower mean mree than men when the portable handheld device was used (Table 3). What happens if you present these data in relative terms (kcal/kg)? We were also interested in these findings and appreciate your comment. As the female cohort was especially small, it is difficult to characterize what happened in the females versus the males. As described in above, we did not conduct any statistics in regards to whether the difference between the mree between the women and men was significantly different. Generally, the BMI was higher in the sample of women compared to the men (see Table 1). Why the increase in mree of women did not occur with the MedGem was not clear to us but would be worthy of further research. As for presenting the data in relative terms, this could certainly be of value in a larger sample. However, the mree difference between the males and the females was very small and therefore this would likely not be of significance (see Table 3).

7 8. Thus, this study rejects the null hypothesis as there was some level of agreement between the mree values from the two devices. The authors may want to consider revising this statement. A paired t-test in this case would test the null hypothesis that there was no difference between the two measurements. Thank you for your comment. The level of agreement was measured in two ways: pairedsamples t-tests and Bland Altman analysis. Please see response to question #1. Since there was no significant difference observed between the mree from the two devices, this would indicate that there was some level of agreement between the two and the null hypothesis would be rejected. 9. If possible, I would be very interested in a comparison between the prediction equations and mree in this manuscript. That is an excellent question and an opportunity for further research, but unfortunately was beyond the scope of this project.