From the coding guidelines :
Documentation for BMI, Depth of Non-pressure ulcers, Pressure Ulcer Stages, Coma Scale, and NIH Stroke Scale
For the Body Mass Index (BMI), depth of non-pressure chronic ulcers, pressure ulcer stage, coma scale, and NIH stroke scale (NIHSS) codes, code assignment may be based on medical record documentation from clinicians who are not the patient’s provider (i.e., physician or other qualified healthcare practitioner legally accountable for establishing the patient’s diagnosis), since this information is typically documented by other clinicians involved in the care of the patient (e.g., a dietitian often documents the BMI, a nurse often documents the pressure ulcer stages, and an emergency medical technician often documents the coma scale). However, the associated diagnosis (such as overweight, obesity, acute stroke, or pressure ulcer) must be documented by the patient’s provider. If there is conflicting medical record documentation, either from the same clinician or different clinicians, the patient’s attending provider should be queried for clarification.
The BMI, coma scale, and NIHSS codes should only be reported as secondary diagnoses.