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Body mass index adjustments in children with early onset scoliosis: arm span BMI
Michael Trask1, Scott Yang2, Apeksha Gupta1
1Seattle Children's Hospital, Seattle, WA, USA.
Insights
Arm span provides a more accurate nutritional assessment for children with early onset scoliosis (EOS) than standard height measurements. This method reveals lower body mass index (BMI) percentiles, better reflecting their true nutritional status.
Area of Science:
- Pediatric Orthopedics
- Nutritional Assessment
- Biometrics
Background:
- Children with early onset scoliosis (EOS) often have reduced height due to spinal curvature.
- Height is typically used to calculate Body Mass Index (BMI) and assess nutritional status.
- Arm span is currently used as a surrogate for height in pulmonary function tests for EOS patients.
Purpose of the Study:
- To evaluate the accuracy of nutritional assessment in children with EOS using arm span versus measured height.
- To determine the discrepancy in Body Mass Index (BMI) and BMI percentile (BMI%ile) calculations when using arm span as a proxy for height.
Main Methods:
- Calculated BMI and BMI%ile using both measured height and arm span for children with EOS.
- Employed Wilcoxon signed-rank test to compare height-based BMI (BMI) with arm span-based BMI (asBMI) and BMI%iles.
- Utilized Spearman correlation and adjusted linear models to analyze the influence of age and coronal curve angle on BMI differences.
Main Results:
- Arm span-based BMI (asBMI) consistently indicated lower nutritional status compared to height-based BMI.
- The percentage of patients with a BMI%ile < 1% was significantly higher using arm span (44.4%) versus height (15.6%).
- The difference between BMI and asBMI correlated with coronal curve magnitude, increasing by 0.0294 kg/m² per degree of Cobb angle (p=0.0062).
Conclusions:
- Arm span provides a more accurate nutritional assessment in children with EOS than standard height measurements.
- Height-based BMI overestimates nutritional status in this pediatric population, particularly with larger coronal curve angles.
Purpose:
Body mass index (BMI), is a nutritional index based on standing height and weight. Children with early onset scoliosis (EOS) have shorter height due to their spine curvature. In these patients' pulmonary function tests, which are also based off height, arm span is standardly used as a surrogate for height to allow for normative comparisons. Arm span has not been used for nutritional assessments in children with EOS.
Methods:
We used both arm span and measured height to calculate BMI, and BMI as a percent of predicted published norms (BMI%ile) to assess the error produced using height in this population of children. We used a Wilcoxon signed-rank test to compare standard height BMI (BMI) vs arm span BMI (asBMI) and BMI%iles, Spearman correlation to assess the influence of age or coronal curve angle on any differences, and an adjusted linear model for the coronal curve's impact on BMI.
Results:
BMI and BMI%ile consistently over-estimated nutritional status compared to asBMI with substitution of arm span for height. 15.6% of patients had a BMI%ile of < 1% using height compared to 44.4% using arm span. The difference between BMI and asBMI correlated with the coronal curve magnitude but not with age. The adjusted linear model showed that for each degree of Cobb angle, the difference between BMI and asBMI increased by 0.0294 kg/m2 (p = 0.0062).
Conclusion:
Arm span BMI reveals lower, more accurate nutritional status in children with EOS than standard height BMI.
Level Of Evidence:
IV.
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