(A) When using a VAS, the patient is asked to mark a 10 cm line at a point that corresponds to the degree of pain. The VAS score is the distance in millimeters from the left end of the line to the patient's mark. (B) When using an NRS, the patient indicates the number that corresponds to pain severity, either verbally or by marking the scale.
VAS: visual analog scale; NRS: numeric rating scale.