Clinically Significant Differences in the Visual Analog Pain Scale in Acute Vasoocclusive Sickle Cell Crisis

Abstract

This study sought to determine the minimum clinically significant change in the visual analog scale (VAS) during the Emergency Department (ED) treatment of adult vasoocclusive sickle cell crisis (VOC). Sickle cell anemia patients presenting to the ED with their typical VOC pain had a 100 mm VAS administered prior to each of up to three standard analgesic injections administered as part of a treatment protocol. At each assessment, subjects were asked to describe their pain as “much better,” a “little better,” “the same,” “a little worse,” or “much worse.” The change in the VAS (ΔVAS) between assessments was measured. The main outcome of the measurement was change in the VAS associated with a description of a change in pain of “a little less” or “a little more.” Seventy four subjects presented with initially high pain scores [VAS = 79.47 mm, 95% confidence interval (CI) = 75.99 to 82.95 mm]. In the “little better/little worse” combined group, the ΔVAS was 13.5 mm (95% CI = 11.25 cm to 15.74 cm). A change in the 100 mm VAS of 13.5 mm is the minimum clinically significant change during ED treatment of VOC. A ΔVAS <13.5 mm may not be clinically important. This finding may assist the clinician in the assessment of pain improvement for adult sickle cell patients with VOC.