MDS Alert

Know how the height/weight calculation impacts your coding choices.

You may have heard whispers about residents who are morbidly obese or have a certain body mass index (BMI) boosts your facility’s reimbursement through an additional point for the non-therapy ancillary (NTA) component of the Patient-Driven Payment Model (PDPM).

The number 40 has been bandied about as the “magic number” for the NTA point because a person who has a BMI of 40 or over is generally considered to be morbidly obese. Read on to find out more about how to figure out a resident’s BMI — and a crucial piece of advice concerning diagnoses.

Know BMI and How to Calculate It

Both ICD-10 and the Centers for Disease Control and Prevention (CDC) describe BMI as being “a person’s weight in kilograms divided by the square of height in meters.” So, the calculation for a resident who is 5 feet 5 inches tall and weighs 150 pounds (times a factor of 703 to convert from standard U.S. measurements to metric), would look like this:

            (150 ÷ 652) x 703 = 24.96

However, you don’t need to get your calculator out just to figure out a resident’s BMI. “An easy way to calculate this is to go to the BMI calculator available on the CDC website,” says Chelle Johnson, CPMA, CPC, CPCO, CPPM, CEMC, AAPC Fellow, billing/credentialing/auditing/coding coordinator at County of Stanislaus Health Services Agency in Modesto, California.

Resource: Find the CDC calculate here:  www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html.

Know How BMI Affects Code Choice

Unfortunately, the ICD-10 codes do not correspond exactly with the CDC’s definitions of underweight, normal, overweight, or obese. The BMI code set Z68.1 (Body mass index (BMI) 19.9 or less, adult), for example, covers adults designated by the CDC as underweight and normal, while the normal range continues through Z68.1 to Z68.24 (Body mass index (BMI) 24.0-24.9, adult). And a CDC designation of obese corresponds with both the Z68.3- and Z68.4- codes, as can be seen in the following table:

Know the Other Codes That Link with BMI

Naturally, the BMI codes also link with the overweight and obesity codes found in E66. In fact, a note accompanying E66 in ICD-10 tells you to “use additional code to identify body mass index (BMI) if known.”

The CDC does not define what constitutes morbid or severe obesity. The consensus opinion in the medical community, however, is that individuals with a BMI greater than 40 would fall into this category, tying Z68.4- to E66.01 (Morbid (severe) obesity due to excess calories) and E66.2 (Morbid (severe) obesity with alveolar hypoventilation). But, as Johnson stresses, the diagnosis must be left to the provider.

And as for individuals in the obese category, ICD-10 provides two codes that ascribe causes to the obesity - E66.0- (Obesity due to excess calories) and E66.1 (Drug-induced obesity) — and two general codes - E66.8 (Other obesity) and E66.9 (Obesity, unspecified) — that do not. This can create yet another coding headache.

“It would be a rare occurrence that the unspecified code would be used, as the physician should always be addressing a BMI of 30.0 of higher with a plan of care that should identify the cause and how to address the condition,” Johnson says.

Important: Remember that documentation is crucial. If a resident’s physician has noted that the resident is morbidly obese, then that is sufficient to use as a diagnosis; you don’t need to find evidence of labs or do any calculations, says Carol Maher, RN-BC, RAC-MT, RAC-CT, CPC, director of education at Hansen Hunter & Co. in Beaverton, Oregon.