Accuracy of equations for estimating resting energy expenditure in children and adolescents living with phenylketonuria

BackgroundMeasuring resting energy expenditure (REE) in individuals living with phenylketonuria (PKU) using indirect calorimetry (IC) is unusual in healthcare facilities because it requires specific protocols and expensive equipment. Considering that determining REE is crucial for devising nutritional strategies for the management of PKU, the aim of this study was to identify the predictive equations that provide the best estimates of REE in children and adolescents living with PKU and to propose a predictive equation for determining REE in this population.MethodsAn REE concordance study was conducted with children and adolescents living with PKU. Anthropometric and body composition assessments using bioimpedance and REE assessment using IC were performed. The results were compared to 29 predictive equations.ResultsFifty-four children and adolescents were evaluated. The REE obtained using IC differed from all estimated REE, except Henry's equation for male children (p = 0.058). Only this equation showed good agreement (0.900) with IC. Eight variables were associated with the REE obtained using IC with emphasis on fat-free mass (kg) (r = 0.786), weight (r = 0.775), height (r = 0.759) and blood phenylalanine (r = 0.503). With these variables, three REE equations were suggested, with R2 = 0.660, 0.635 and 0.618, respectively, and the third equation, which involves weight and height, showed adequate sample size for a statistical power of 0.942.ConclusionMost equations, not specific for individuals living with PKU, overestimate the REE of this population. We propose a predictive equation for assessing REE for children and adolescents living with PKU to be used in settings where IC is not available. Most energy expenditure prediction equations overestimate the resting energy expenditure (REE) of individuals living with phenylketonuria (PKU). We propose a simple predictive equation to assess REE for children and adolescents living with PKU to be used where indirect calorimetry is not available.image A summary list of available resting energy expenditure (REE) prediction equations for children and adolescents is provided.Most of the available REE prediction equations for children and adolescents overestimate the REE of children and adolescents with phenylketonuria (PKU).Age, weight, height, body mass index, weight-for-age index, fat-free mass and blood phenylalanine were significantly associated with the REE of children and adolescents with PKU.Three predictive equation models were developed and internally validated to estimate the REE of children and adolescents with PKU in the absence of indirect calorimetry.