Resting Energy Expenditure in Neurofibromatosis Type 1: Indirect Calorimetry versus Predictive Equations

Abstract

Increased resting metabolism, by indirect calorimetry (IC), has been observed in neurofibromatosis type 1 (NF1) patients as compared to in the unaffected population. As IC is not an easily available method, the present study aimed to measure resting energy expenditure (REE) in adults with NF1 by using IC and determine the most appropriate equation to estimate the predictive value of this variable in clinical practice. Twenty-six NF1 patients aged between 18 and 45 years underwent nutritional assessment, including weight, height, and body mass index. Body composition was measured by dual energy x-ray absorptiometry (DXA). RMR was measured by IC (mREE) and by eight different equations (pREE). Statistical analysis were carried out by Kolmogorov-Smirnov test, paired student's t test, and Bland and Altman plots. The mean age was 34.3 ± 6.1 years. The mean mREE was 1633.9 ± 471.1 kcal, and the pREE ranged from 1244.6 ± 239.9 kcal to 1519.9 ± 271.1. The best predictive REE equation for individuals with NF1 was the WHO equation (weight and height), given its small difference (although significant; P = 0.041) from the values obtained using the gold standard, good median of adequacy (92.0%), and high accuracy (46.2%). This study showed that all the eight predictive equations underestimated REE in NF1 patients (with large differences and low accuracy when compared to a gold standard method). IC is the preferred way to avoid over or underestimation of REE in NF1 patients.