The Minimal Important Difference in Borg Dyspnea Score in Pulmonary Arterial Hypertension

Despite therapeutic advances, pulmonary arterial hypertension remains a disease without a cure. Focusing on symptoms, such as dyspnea, is an important part of assessing response to therapy.

To determine the minimal important differences for the Borg dyspnea score and the Borg fatigue score in adult patients undergoing initial therapy for pulmonary arterial hypertension.

We studied 129 patients enrolled between 2003 and 2013 in the Pulmonary Arterial Hypertension Program registry at Johns Hopkins University Hospital in Baltimore, Maryland. We analyzed baseline demographics, clinical characteristics, 6-minute-walk test distance, and Borg dyspnea and fatigue scores at baseline and at follow up 3 months after initiation of pulmonary arterial hypertension therapy. The minimal important differences for the Borg dyspnea and fatigue scores were determined using distributional and anchor-based methods, using 6-minute-walk test distance as the anchor.

Most subjects were in New York Heart Association functional class II or III and had moderate to severe pulmonary arterial hypertension. The baseline Borg dyspnea score was 3.4 ± 1.9 units; the baseline Borg fatigue score was 2.8 ± 2.2 units. After therapy, the average change in the dyspnea score was -0.16 ± 1.9 units and the average change in the fatigue score was -0.21 ± 2.4 units. Using distributional methods, the minimum important difference for Borg dyspnea score ranged from 0.7 to 1.24 units and for Borg fatigue score ranged from 0.73 to 1.39 units. Using anchor-based methods, the minimum important difference for the Borg dyspnea scales was 0.36; this could not be calculated for the Borg fatigue score.

Using distributional and anchor-based methods, we estimate the minimum important difference for Borg dyspnea scale in pulmonary arterial hypertension is approximately 0.9 units. Using distributional methods only, we estimate the minimum important difference for the Borg fatigue scale is around 1 unit. Further studies are needed to determine the clinical utility of these scores in patients with pulmonary arterial hypertension.