Introduction
Pain, NRS, pain
Two of the most common patient-reported outcomes (PRO) instruments to assess pain intensity are the numerical rating scale (NRS), where patients select a number from 0 to 10 corresponding to their experienced pain level, and the visual analog scale (VAS), where patients are asked to mark their pain level on a line (usually 100-mm) between two endpoints. Both the NRS and VAS include “anchor” text at each end. Whereas the anchor text for 0 is typically “no pain”, the anchor text for the highest pain level varies greatly [Pain as a symptom is a personal sensory experience [