Figure 8.1: VAS for Dry Mouth Symptoms

VAS allow an estimate of the severity of a symptom and the ability to monitor changes over time. The subject responds by placing a vertical mark corresponding to the intensity of their symptom across the unmarked 100mm horizontal line. Verbal "anchors" pertinent to the question -- "dry as a desert" and "not dry at all" in this example -- are placed at either end. The response is determined by measuring the distance to the patient's mark from the left end of the line.