Minimally important dyspnoea, fatigue changes in PAH patients defined

By Eleanor McDermid

Researchers say that a change of around 1 unit in Borg dyspnoea or fatigue scores signifies an important change in patients with pulmonary arterial hypertension (PAH).

Stephen Mathai (Johns Hopkins University School of Medicine, Baltimore, Maryland, USA) and co-workers believe their findings have "important implications for clinical management and future clinical trials of patients with PAH", although they stress that they first need further validation.

They say that defining the size of an important change helps to justify escalation of medication and to gauge patients' perceptions of their management.

The study involved 129 PAH patients, most of whom had idiopathic or connective tissue disease-associated PAH. At baseline, their average Borg dyspnoea score (BDS) and Borg fatigue score (BFS) were 3.4 and 2.8 units, respectively. These improved by an average of 0.16 and 0.21 units, respectively, during treatment, while their average 6-minute walk distance (6MWD) improved by 13 metres.

As described in the Annals of the American Thoracic Society, the researchers used a variety of methods to determine the minimally importance difference (MID) for BDS and BFS. Anchor-based methodology produced an MID of 0.36 for the BDS; however, it could not calculate an MID for BFS because of poor correlation with the anchor - the MID of the 6MWD.

The team also used distributional methods, namely, effect size, standard response mean, standard error of the measurement and the standard deviation of the baseline measure multiplied by 0.5. The MIDs according to these methods ranged from 0.70 to 1.24 for the BDS and from 0.73 to 1.39 for the BFS.

Triangulation (ie, cross verification of all the methods) produced an estimated MID of 0.9 units for the BDS and 1.0 unit for the BFS, which the team notes is similar to the proposed MID for BDS in patients with chronic obstructive pulmonary disease.

"Our findings suggest that small changes in Borg dyspnea and fatigue scores are noticeable to the patient, potentially clinically relevant, and therefore may serve as targets for therapeutic intervention", conclude Mathai et al.

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