Objectives: The objective was to describe the association between verbal descriptors of nausea severity and visual analog scale (VAS) ratings in an undifferentiated emergency department (ED) population and to calculate the minimum clinically significant difference (MCSD) in VAS rating of nausea severity in this population.
Methods: A prospective observational study was conducted at three EDs on a convenience sample of stable, consenting adult patients presenting with nausea as part of their symptom complex. Data included demographics, adjectival description of nausea severity (none, mild, moderate, or severe), and VAS rating (standard 100-mm line) at enrollment, 30 minutes, and 60 minutes. At 30 and 60 minutes they were also asked to describe any change in nausea severity from the previous rating ("a lot less,""a little less,""the same,""a little more,""a lot more"). The MCSD was defined as the average VAS change when a patient reported "a little less" or "a little more" nausea.
Results: A total of 247 patients provided 693 matched adjectival ratings and VAS scores. Median age was 45 years, and 100 (40%) were male. The median VAS measures for none, mild, moderate, and severe nausea were 2, 23, 53, and 83 mm, respectively. VAS distributions in the verbal categories were statistically different from each other (Spearman rank correlation coefficient = 0.90; p < 0.0001). The MCSD was 22 mm (95% CI = 20 to 24 mm).
Conclusions: There is very good correlation between verbal descriptors of nausea and VAS ratings. The MCSD for VAS nausea ratings in an ED population is 22 mm.