Predictive fat mass equations for spinal muscular atrophy type I children: Development and internal validation

Area of Science:

• Pediatrics
• Biostatistics
• Clinical Nutrition

Background:

• Body composition assessment is crucial for spinal muscular atrophy type I (SMA I) patients.
• Traditional metrics like weight and BMI are unreliable for SMA I.
• Current methods require specialized settings, lacking disease-specific field tools.

Purpose of the Study:

• Develop predictive fat mass equations for SMA I children using simple measurements.
• Compare the accuracy of newly developed disease-specific equations against existing ones.

Main Methods:

• Utilized demographic, clinical, and anthropometric data from 153 SMA I patients.
• Employed restricted cubic splines to account for non-linear relationships.
• Developed and internally validated predictive models for fat mass fraction.

Main Results:

• A selected model using sex, age, calf circumference, and skinfold thicknesses demonstrated high predictive ability (R² = 0.72).
• The disease-specific equation proved more accurate than general fat mass equations.
• Nusinersen treatment did not significantly improve prediction accuracy.

Conclusions:

• The developed prediction model enables accurate body composition assessment in SMA I children.
• The model relies on simple, widely available measures.
• This provides a practical field method for SMA I body composition evaluation.