Defining the Minimal Important Difference for the Visual Analogue Scale Assessing Dyspnea in Patients with Malignant Pleural Effusions |
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| Authors: | Eleanor K Mishra John P Corcoran Robert J Hallifax John Stradling Nicholas A Maskell Najib M Rahman |
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| Institution: | 1. Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit, Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom.; 2. University of Bristol, Bristol, United Kingdom.; Postgraduate Institute of Medical Education and Research, INDIA, |
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| Abstract: | BackgroundThe minimal important difference (MID) is essential for interpreting the results of randomised controlled trials (RCTs). Despite a number of RCTs in patients with malignant pleural effusions (MPEs) which use the visual analogue scale for dyspnea (VASD) as an outcome measure, the MID has not been established.MethodsPatients with suspected MPE undergoing a pleural procedure recorded their baseline VASD and their post-procedure VASD (24 hours after the pleural drainage), and in parallel assessed their breathlessness on a 7 point Likert scale.FindingsThe mean decrease in VASD in patients with a MPE reporting a ‘small but just worthwhile decrease’ in their dyspnea (i.e. equivalent to the MID) was 19mm (95% CI 14-24mm). The mean drainage volume required to produce a change in VASD of 19mm was 760ml.InterpretationThe mean MID for the VASD in patients with a MPE undergoing a pleural procedure is 19mm (95% CI 14-24mm). Thus choosing an improvement of 19mm in the VASD would be justifiable in the design and analysis of future MPE studies. |
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