Misclassification of child body mass index from cut-points defined by rounded percentiles instead of Z-scores

Area of Science:

• Pediatric Nutrition
• Growth Monitoring
• Biostatistics

Background:

• Accurate assessment of child growth is crucial for identifying nutritional status.
• Body Mass Index (BMI) is a common metric, but its interpretation in early childhood requires careful consideration of standardized references.
• The use of rounded percentiles versus Z-scores for BMI cut-points can lead to discrepancies in classification.

Purpose of the Study:

• To evaluate the extent of misclassification in early childhood growth assessment.
• To compare the diagnostic accuracy of BMI cut-points defined by rounded percentiles versus Z-scores.
• To highlight the implications of using different classification methods on study comparability.

Main Methods:

• A cross-sectional study was conducted using data from 5836 children under 6 years old.
• Body Mass Index for Age Z-scores were calculated using World Health Organization growth standards.
• Misclassification rates were determined by comparing BMI categories derived from rounded percentiles against those derived from Z-score cut-points.

Main Results:

• The use of rounded percentiles resulted in different proportions of children classified as wasted, at risk of overweight, overweight, and obese compared to Z-scores.
• Overall, 2% of children were misclassified, with significant misclassification rates observed for wasted (13%) and obese (14%) categories.
• Discrepancies in classification were noted, particularly at the extremes of the BMI distribution.

Conclusions:

• The use of rounded percentiles for BMI cut-points in early childhood leads to significant misclassification of growth status.
• This misclassification can hinder accurate identification of children's nutritional status and limit the comparability of research findings.
• Standardized use of Z-scores is recommended for consistent and accurate child growth assessment.