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A new total body potassium method to estimate total body skeletal muscle mass in children
ZiMian Wang1, Stanley Heshka, Angelo Pietrobelli
1Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, New York, NY 10025, USA. zw28@columbia.edu
Insights
Adult models for estimating skeletal muscle mass (SM) using total body potassium (TBK) are not suitable for children. This study developed and validated new pediatric-specific equations for predicting skeletal muscle mass in children using TBK measurements.
Area of Science:
- Pediatric physiology
- Body composition analysis
- Biomedical engineering
Background:
- Skeletal muscle mass (SM) estimation is crucial for assessing child growth and health.
- Existing models for SM estimation based on total body potassium (TBK) are validated for adults but their applicability in children is unknown.
- Accurate body composition assessment in children is essential for nutritional and developmental studies.
Purpose of the Study:
- To derive and validate a pediatric-specific prediction equation for skeletal muscle mass (SM) using total body potassium (TBK).
- To determine if adult TBK-based SM prediction models are applicable to pediatric populations.
- To establish reliable methods for assessing skeletal muscle mass in children.
Main Methods:
- Utilized Magnetic Resonance Imaging (MRI) to measure skeletal muscle mass (SM) as the criterion standard.
- Employed whole body (40)K counting (WBC) to measure total body potassium (TBK) in 116 healthy children (ages 5-17).
- Developed empirical prediction equations for SM based on TBK, incorporating biological factors in a general linear model.
Main Results:
- A strong linear correlation (r = 0.984) was found between TBK and SM in children.
- The SM:TBK ratio in children (0.0071 kg/mmol) was significantly lower than in adults (0.0082 kg/mmol).
- Developed two pediatric-specific equations: SM = 0.0085.TBK - 2.83 (r(2)=0.97) and a more complex model including weight, height, and race.
Conclusions:
- The adult model for predicting skeletal muscle mass from total body potassium is not applicable to children.
- New empirical prediction equations based on TBK have been developed and validated for pediatric use.
- These pediatric equations are valuable tools for research in child nutrition, growth, and development.
Abstract:
A whole body skeletal muscle [(SM); kg] mass estimation model, based on total body potassium [(TBK); mmol] measured by whole body (40)K counting (WBC) was developed (SM = 0.0082.TBK) and validated in adults in a previous study. It is unknown whether the adult TBK SM prediction model is applicable for pediatric use. The aim of this study was to derive and validate a pediatric TBK SM prediction equation. SM measured by MRI was used as the criterion and TBK was measured by WBC. The protocol was completed in 116 healthy children, 66 males and 50 females, 11.7 +/- 3.5 y (mean +/- SD, range = 5-17 y). A strong linear correlation was observed between TBK and SM (r = 0.984; P < 0.001). The SM:TBK ratio was 0.0071 +/- 0.0008 kg/mmol in the children studied, much lower than the corresponding value of 0.0082 kg/mmol in adults. An empirical SM prediction equation was developed using TBK alone: SM = 0.0085.TBK - 2.83, r(2) = 0.97, SEE = 1.39 kg. Bland-Altman analysis did not disclose a significant bias in the prediction of SM. When biological factors entered along with TBK in the general linear model, another prediction equation was developed: SM = 5.52 + 0.001.TBK (mmol) + 0.081.weight (kg) - 0.049.height (cm) + 0.00004.TBK . height + race (-0.60 for Caucasian, 0.49 for African-American, and 0 for Hispanic). Because the adult TBK SM prediction model is not applicable for pediatric use, this study provides new empirical TBK SM prediction equations that should prove useful for studies on nutrition, growth, and development in children.
