FileMaker Pro - Calculating BMI

Kevin asked about calculating and classifying a BMI using FileMaker Pro.  The two formulas will be included in the tutorials for the eBook I am writing.  In this blog, I will describe how to calculate the BMI.  In the Metabolic Syndrome Database the patient's height in feet and inches are separate fields in the Patient table.  Generally, the height of an adult does not change.  However, Kevin, as a pediatric nursing practitioner student, should include height in the visit table.   A child's height will change with age.

Use the CDC BMI calculation appropriate for the client.  According to the CDC, the adult BMI formula is (Source: http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html )

Measurement Units	Formula and Calculation
Kilograms and meters (or centimeters)	Formula: weight (kg) / [height (m)]2 With the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters. Example: Weight = 68 kg, Height = 165 cm (1.65 m) Calculation: 68 ÷ (1.65)2 = 24.98
Pounds and inches	Formula: weight (lb) / [height (in)]2 x 703 Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703. Example: Weight = 150 lbs, Height = 5'5" (65") Calculation: [150 ÷ (65)2] x 703 = 24.96

I prefer to create and edit FileMaker Pro tables from the File > Manage > Database view.  The first step is to instruct FileMaker that the field is a calculated value.  That instruction opens a window to enter the formula.  A really easy way to create the formula is to choose the fields from the pertinent tables from the tables drop-down menu.  You do not need to insert an equals sign (=) before a formula because FileMaker does that for you.

Next, I had to create a calculated field to determine height in inches.  The formula noted below in the Visit table is
(Patient::HtFt*12)+Patient::HtIn

The two :: tells FileMaker to obtain the value from the Patient table. HtFt and HtIn are two fields in the Patient table. The caret (^) is used to instruct FileMaker to square the height in inches.

The formula for BMI is (Weight * 703)/(Height In^2)

That is all there is to creating the BMI formula.  Kevin would need to use the BMI formula for children.  It can be adapted from http://apps.nccd.cdc.gov/dnpabmi/ 

Catching Up and more on FileMaker Pro

There is much to share and just not enough time! :-)

I have been working on four lessons for one of the classes I teach on how to use Excel and FileMaker Pro.  I wrote out the content because there is not a book that addresses how to use Excel and FileMaker Pro from a nursing perspective.  

The good news, is that I believe I have FileMaker Pro figured out.  I developed a Metabolic Syndrome Registry database and have incorporated calculations that:

• Calculate height in total inches height in feet and inches
• Calculate the BMI from height in inches and weight in pounds
• Analyze the BMI for World Health Organization Obesity classifications
• Analyze the weight goal based upon BMI classifications

The similarities between Excel formulas and FileMake Pro are remarkable.  Where you use a comma in an Excel formula, you use a semicolon in FileMaker Pro.  The creation of concatenation is identical.  Concatenation is where you link two fields.  For example if you have systolic blood pressure in one field and systolic blood pressure in another you can create a new field showing 120/80.  

I really like the fact that FileMaker Pro does not use words that are so "techie."  For example, the term layouts is used (the default is single form, running forms, and table view) for any table or queries.  The term "queries" is not used - just a different layout. The term "script" is used instead of "macro."