Which of the following is NOT a vital sign?

Body mass index (BMI) is indeed not classified as a vital sign. Vital signs typically encompass a collection of measurements that indicate the state of a person's essential bodily functions, including body temperature, pulse rate, and blood pressure. These metrics are integral in assessing a patient's immediate health status and responses to treatments.

In contrast, body mass index is a numerical value derived from an individual’s height and weight, and it is used primarily to evaluate body composition and categorize weight status (e.g., underweight, normal weight, overweight, obesity). While BMI can provide valuable information regarding health and potential risks associated with weight, it does not reflect immediate physiological functions or conditions in the same way that vital signs do. This distinction clarifies why body mass index does not belong to the group of vital signs.