Add a calculated field (BMI, eGFR, QTc and more)
On a Number field, switch on Calculated field under Validation, choose a Formula and map each input to a question on the form. The field is filled automatically and is read-only at data entry.
Where to find it
Form editor > Number question > Validation > Calculated field
Before you start
- The form is a draft. Approved forms are changed through a new version.
Add the calculation
Add or open a Number field question.
Under Validation, switch on Calculated field.
Choose a Formula.
Under Map inputs to form questions, link each input (for example weight and height) to its question.
Optionally try it in Test calculator, then click Save Changes.
The field shows an Auto-derived badge.
Available formulas
- BMI, BSA (Mosteller and Du Bois) and waist-hip ratio.
- Mean arterial pressure (MAP) and pulse pressure.
- eGFR (CKD-EPI 2021, race-free) and creatinine clearance (Cockcroft-Gault).
- QTc (Bazett and Fridericia) and QTcF from heart rate.
- Age from date of birth, and minutes or hours between two date-times.
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