Primary Care Coding Alert

In this case, should I document cachexia as it’s a stronger term (in my understanding), or should I document underweight? Also, in either case, do I code the appropriate BMI?

AAPC Forum Participant

Answer: Cachexia, coded to R64 (Cachexia), is a condition that, as its synonym tells you, involves muscle wasting and extreme, unintended weight loss. It is also a symptom of a number of chronic diseases like AIDS and cancer, which explains the instruction to code first any underlying condition, if known, that accompanies the cachexia.

This is very different from R63.6 (Underweight), which is a clinical determination your provider will make based on a patient’s body mass index (BMI), defined by the Centers for Disease Control and Prevention (CDC) as a BMI below 18.5 (www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html). This means you must query your provider to determine which of the two conditions should be documented.

As for coding the patient’s BMI, R63.6 comes with an instructional note to use additional code to identify BMI if known, most likely Z68.1 (Body mass index [BMI] 19.9 or less, adult). You can also use Z68.1 with R64, as ICD-10 guideline 1.C.21.c.3 tells you that “BMI codes should only be assigned when there is an associated, reportable diagnosis.”

And remember: ICD-10 guideline 1.B.14 allows you to report a BMI code if a clinician other than your provider who is involved in the care of the patient, such as a dietitian, has documented it. But if the patient’s BMI has not been documented, you cannot infer a code from Z68.- based on the patient’s height and weight.