American Board of Family Medicine (ABFM) Practice Exam 2025 - Free ABFM Practice Questions and Study Guide

The severity of anorexia nervosa is primarily assessed using body mass index (BMI) as it provides a quantitative measure of an individual's weight relative to their height. In clinical practice, BMI is used to classify the severity of anorexia nervosa into different categories, which helps in determining the level of care that may be necessary for treatment. For instance, lower BMI values indicate more severe forms of anorexia nervosa, guiding clinicians in understanding the extent of malnutrition and related medical risks.

While refusal to eat, presence of amenorrhea, and orthostatic changes in pulse or blood pressure are indeed relevant aspects of anorexia nervosa that can help in a comprehensive assessment of the disorder, they do not serve as the primary criteria for classifying its severity. Refusal to eat is a behavioral manifestation but does not quantify the health risks associated with weight loss. Amenorrhea may indicate the physiological effects of the disorder, but it is not a strict diagnostic criterion, as some individuals with anorexia may still have menstrual cycles. Orthostatic changes can reveal complications related to the disorder but are more indicative of dehydration and autonomic instability rather than directly correlating with the classification of severity based on weight.

Thus, BMI stands out as the most objective measure