Measuring body mass index (BMI)requires the following equation:
BMI = (weight (lb) ÷ height² (in)) x 703

The Result?

BMI = A physiologically misleading indicator used to classify health status. Misleading because weight divided by height squared (x 703 to make up for the metric system) tells us nothing about a patient’s bone density or muscle mass, both of which tell us a great deal about a person’s physical health. This misleading indicator is then broken into categories that patients are often bucketed into: underweight (below 18.5), normal (18.5-24.9), overweight (25.0-29.9), obese (30.0-39.9), morbidly obese (over 40) without consideration of gender, ethnicity, age, or athleticism variances. Well-conditioned athletes and weightlifters often have notoriously high BMI’s due to exceptional bone health and increased muscle mass.

Clinical Significance

Coding Clinic addresses in Fourth Quarter 2018 that “obesity and morbid obesity are always clinically significant and reportable when documented by the provider. In addition, if documented, the body mass index (BMI) code may be coded in addition to the obesity or morbid obesity code.” But what happens when the provider has not documented a diagnosis? One cannot assume the clinical significance of a number without an associated diagnosis. Without more information about a patient, we cannot be sure that the elevated BMI requires a diagnosis or is simply a numerical finding without clinical relevance because the patient is a world-renowned bodybuilder.

An Inherent Issue

Clinical documentation integrity (CDI) specialists and coders are often trained to look for the BMI and the accompanying appearance of an associated diagnosis when a high or low value is noted. There is an inherent issue in this practice. Recall the inpatient guidelines for reporting additional diagnoses (Section III. Reporting Additional Diagnoses: General Rules for Other (Additional) Diagnoses):

“For reporting purposes, the definition for ‘other diagnoses’ is interpreted as additional conditions that affect patient care in terms of requiring: clinical evaluation; or therapeutic treatment; or diagnostic procedures; or extended length of hospital stay; or increased nursing care and/or treatment.”

The burden of proof rests on the CDI specialist or coder to demonstrate that a condition met “other” diagnosis criteria yet was not documented when initiating a query. Aside from being a questionable result to a math equation, how did the patient’s elevated or low BMI impact their hospital stay?

Many CDI specialists default back to “weight-based medications.” Can you identify the weight-based medications in a patient who did not receive anesthesia? Every nurse took a course in medication math to get through nursing school. If your patient received a heparin infusion at a weight-based dose, did a weight of 285 pounds in a 5’5” patient impact nursing care more than a weight of 285 pounds in a 6’5” patient would have when calculating a dose? There is an argument for therapeutic treatment varying but before you ask the question, be sure your argument is sound.

Indicators

There are indicators to look for that justify that some BMI-related diagnoses may be clinically significant. Read the nurse’s notes. Fully dependent or even partially dependent patients requiring “max assist” or “OOB w/ assist x2” demonstrates that additional nursing care was required. Specialty beds come at a premium and provide support to patients above and beyond that of a traditional inpatient bed. Nutrition consults to help a patient with a BMI of 17.0 gain weight are obviously targeted treatment.

Be on the lookout for “other” reasons for inaccurate BMI and avoid falling into the traps. Patients and clinicians are usually not accurate when guessing a patient’s weight. If you see a solid even number (say 300 pounds) entered into the electronic medical record, do some digging to see “how” the patient was weighed. Standing scales and bed scales are far more accurate than “self-report.” While it seems very specific, be mindful of bilateral amputees. Most electronic records automatically calculate BMI based on the input height and weight. Any amputee requires special consideration for the percentage of body surface lost.

Performing the CDI role is to assess a patient without the use of your senses. For those with a clinical background that required patient assessment, the CDI role requires that you do the same assessment without ever seeing, touching, or hearing the patient. Querying for accuracy in the patient record takes unique skills and it is important to exercise those skills prudently when attempting to assess a patient with a potentially misleading number.

Need help keeping your Coding and CDI teams up-to-date? Contact us to find out how we can help. Intellis offers in-depth education and training services led by our IQ Team of subject matter experts.