These are the PRIMED Harmonization instructions for body mass index (BMI).
Overall procedure
1. Extract trait measurements using measurement codes and calculations
2. Convert measurement units to expected units, if necessary
3. Apply measurement exclusion criteria, other than statistical outliers
4. Remove statistical outliers
5. Compute a single value per individual for inclusion in analysis
6. Calculate counts of flagged individuals
For BMI, weight and height are used to calculate BMI. Codes for both weight and height are available on this page for download.
Expected units consist of meters for height and kg for weight.
Statistical outliers will also be removed outside of a +/- 6SD from the mean by sex for height and weight before calculating BMI.
Once height and weight have been ascertained, BMI should be calculated using the following formula for height and weight taken at the same timepoint, likely resulting in multiple BMI values for each participant.
BMI (kg/m2) = (Weight in kg)/(Height in m)^2
The following measurements should be excluded from the analysis. Other measurements from an individual may still be included in analysis.
• Age at measurement <18 years
• Exclude measurements taken at Inpatient or Emergency Department visits. Alternatively, keep only measurements taken at Outpatient visits. Take whichever approach is most appropriate for your EHR.
• Exclude measurements for individuals with any of these conditions at the time of BMI measurement:
• Cancer
• Pregnancy (on date of measurement)
Cancer and Pregnancy codes are included in the BMI_Exclusions_and_Flags file.
Statistical outliers will also be removed outside of a +/- 6SD from the mean by sex for BMI after calculation after applying all other exclusions.
A single value per individual is gathered by calculating the mean BMI per person and the age attached to the median age of the measurements used to calculate the BMI.
There are no additional flags for this trait.
