BMI Percentile (Pediatric)

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Description

This phenotype determines the BMI-for-age percentile and associated z-score for patients 2 - 19 years old.

For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age. A child’s weight status is determined using an age- and sex-specific percentile for BMI rather than the BMI categories used for adults. Overweight is defined as a BMI ranging from the 85^thto 95^th percentile and obese is defined as a BMI greater than the 95th percentile for children and teens of the same age and sex.

Limitation

BMI calculation is reliant upon accurate patient height and weight data. Inaccurate height or weight patient data can cause an error in the reported BMI. Missing height or weight data will not return a value for BMI.

Data quality is limited to individual site documentation accuracy, completeness, and variable mapping, which is performed by each site, independently. MPOG, as the coordinating center, reviews data quality at each data upload and monthly via Data Diagnostics and Case Validation tools. This review, while thorough, may not contain all data elements relevant to this phenotype and thus should be carefully reviewed by the user.

Value Type

Numeric

Enumeration

Value	Value Code	Definition

Return Columns

Column Name	Data Type

Granularity

Logic

This phenotype returns the BMI percentile and z-score per case based on the patient's age, sex, height (cm) and weight (kg) at time of surgery.

Step I: Obtain BMI value from its respective collation.

Height and Weight collations have specific valid ranges which are defined in their respective collation documentation. See these collation documents for more information.

Calculated BMI = Weight(kg) / (Height(cm)/100)²
- If either/both Weight(kg) or Height(cm) is a NULL value then,
- Use value documented under MPOG Concept 70253 'Physical Exam - Body Mass Index'. If not available, return NULL

Step II: Determine BMI percentile based on CDC reference tables

**The CDC reference tables list age at the half month point for the entire month; for example, 1.5 months represents 1.0-1.99 months or 1.0 month up to but not including 2.0 months of age

Calculate Age in months, based on mid point for age in years:= (Age in Years * 12) + 6.5
Return BMI percentile for Age

Step III: Calculate the corresponding z-score based on LMS parameters listed in CDC reference table

X: BMI Value
L: Power in the Box-Cox transformation
M: Median
S: Generalized coefficient of variation