Introduction: The authors of the international task force about the management of Dyspnoea recommend assessing sensory and affective components of dyspnoea. The Dyspnoea-12 questionnaire (D-12) allows to assess both components of dyspnoea. D-12 is valid and reliable but its sensitivity to pulmonary rehabilitation was not studied. The aim of this study was to estimate the minimal important difference (MID) for D-12 in COPD patients undergoing a pulmonary rehabilitation programme (PRP).
Methods: Severe or very severe COPD patients undergoing a PRP were included. Dyspnoea was assessed using D-12, MMRC dyspnoea scale, London chest of Activity of Daily Living questionnaire (LCADL). Quality of life was assessed using Saint-George respiratory questionnaire (SGRQ) and COPD assessment Test (CAT); exercise capacity using 6-Minute walk Test (6MWT) and 1-minute sit to-stand test (1STST). The MID was evaluated using distribution and anchor-based methods.
Results: Sixty patients (age: 64.4 ± 8.2; FEV1 (%): 28.6 ± 8.1) were included. At the end of the PRP, patients had significantly decreased their dyspnoea measured with D-12, MMRC, LCADL (D-12:23.9 ± 8.9 to 17.6 ± 9.4; MMRC: 3 ± 0.7 to 2.2 ± 1.1, LCADL: 38 ± 13.9 to 31.6 ± 11; p < 0.0001). Using the distribution-based analysis, MID of -2.67 (standard error of measurement) or -4.45 (standard deviation) was found. According to methodology, we could only use SGRQ as anchor. With SGRQ as anchor, the receiver operating characteristic curve identified MID for the change in D-12 at -6.1 (sensibility: 58%, specificity: 79%). The correlation with SGRQ was modest (r = 0.33), so the calculated MID should be interpreted with caution.
Conclusion: D-12 is a good tool to assess the decrease of dyspnoea after PR. We propose MID of -6 points. However, Future estimates of MID for the D-12 should use anchors that are more strongly correlated with it.
Keywords: COPD; dyspnoea; evaluation; minimal important difference; pulmonary rehabilitation.
© 2020 John Wiley & Sons Ltd.