Clinically significant changes in nausea as measured on a visual analog scale

Study objective: Our objective is to determine the minimum clinically significant change in nausea as measured on a visual analog scale. Methods: This was a prospective, descriptive, convenience sample study of consenting adults presenting to the emergency department with nausea, excluding intoxicated patients and those with mild nausea (measuring <30 mm on a visual analog scale). Patients rated their nausea severity on a 100-mm visual analog scale and reported whether their nausea was "a lot less," " a little less," "unchanged,'' "a little more," or "a lot more" compared with previous assessments. We defined the minimum clinically significant change as the mean difference in visual analog scale in patients reporting "a little less" or "a little more" nausea. Results: Eighty-three paired visual analog scale measurements were collected from 50 patients. Fifty-eight percent of patients were women, and the mean age was 41 years. Mean changes in visual analog scale with corresponding qualitative descriptors were ''a lot less" in 16 paired measurements (-42.2 mm; 95% confidence interval [CI] -54.9 to -29.5); "a little less" in 34 paired measurements (-15.4 mm; 95% CI -20.0 to -10.8); "no change" in 28 paired measurements (-0.4 mm; 95% CI -5.6 to 4.8); "a little more" in 2 paired measurements (16 mm; 95% CI -86 to 118); and "a lot more" in 3 paired measurements (23.7 mm; 95% CI -5.4 to 52.8). Patients reported "a little more" or "a little less'' nausea in 36 paired measurements, with a mean change in visual analog scale of 15.4 mm (95% CI 11.0 to 19.8). Conclusion: The minimum clinically significant visual analog scale change in nausea was 15 mm, which is similar to previous studies of other symptoms, and helps in the interpretation of clinical studies reporting changes in nausea.