Elsevier

American Heart Journal

Volume 164, Issue 2, August 2012, Pages 229-235
American Heart Journal

Clinical Investigation
Congestive Heart Failure
Minimally clinically important difference in chronic breathlessness: Every little helps

https://doi.org/10.1016/j.ahj.2012.05.003Get rights and content

Objectives

The aim of the study was to determine the minimally clinically important difference (MCID) for breathlessness due to chronic heart failure (CHF).

Background

The measurement of breathlessness is difficult because it is subjective and multifactorial. Statistically significant changes in assessment may not be clinically meaningful. This is the first determination of MCID in chronic breathlessness in CHF using patient-rated data.

Methods

Measurements were made as part of a randomized, controlled, crossover trial of morphine, oxycodone, or placebo for breathlessness in CHF. Breathlessness intensity was assessed at baseline and at the end of each intervention (day 4) using 11-point numerical rating scales (NRS), modified Borg (mBorg) scales, and global impression of change (GC) in breathlessness at day 4. From these data, the change in NRS or mBorg associated with a 1-point change in GC was calculated.

Results

Thirty-five patients completed all study interventions, resulting in 105 data sets. We defined MCID as a 1-point change in GC. Regression analysis found that the MCID, including 95% CIs, equaled change in average NRS breathlessness per 24 hours of 0.5 to 2.0 U (P < .001), change in worst NRS breathlessness per 24 hours of 0.4 to 2.9 (P < .001), change in average mBorg score of 0.2 to 2.0 (P < .001), and change in worst mBorg score as between 0.3 and 1.9 (P < .001). Corresponding effect size calculations lay within the 95% CIs for the regression analysis for each measure.

Conclusions

A 1-point change in NRS or mBorg score is a reasonable estimate of the MCID in average daily chronic breathlessness in CHF.

Section snippets

Methods

Measurements were made as part of a randomized, controlled, crossover, double-blind trial of opioids for breathlessness in CHF (International Standard Randomised Controlled Trial Number: 85268059).16 Symptomatic adults with a diagnosis of New York Heart Association III and IV CHF taking standard medical therapy were randomized to oral morphine, oral oxycodone, or placebo. Equianalgesic doses (British National Formulary) of the 2 short-acting opioids were used (morphine 5 mg 4 times per day and

Results

All 35 patients completed the 3 study arms, resulting in 105 complete data sets. The linear gradients, reciprocal linear gradients, and effect sizes (using the model described by Ries13 [2005]) are shown in the Table. The gradient of the line between the 2 estimates is equal to a 1-point change on the GC score. Both regression equation values are based on the gradient of the regression line to calculate the NRS or Borg score, and the corresponding reciprocal gradients based on the calculation

Discussion

This is the first study to demonstrate an MCID for chronic breathlessness in CHF and, to the best of our knowledge, is the first study in chronic breathlessness to assess the MCID for breathlessness as reported by the patient in any disease group. It is a vital piece of missing information for researchers designing studies using intensity of breathlessness as a primary end point. It is also important for physicians in the interpretation of clinical changes observed in their interpretation of

Conclusions

Chronic breathlessness is important to patients and their caregivers as a target for therapeutic intervention. It is important that we can measure the effects of any intervention and assess whether any effects found are clinically relevant; the results of our study suggest that even small improvements are noticeable for people trying to cope with daily breathlessness.

A 1-point change in NRS or mBorg score is a reasonable estimate of the MCID in average daily chronic breathlessness in CHF.

Disclosures

Funding source: This work was supported with a Clinical Research Fellowship for a PhD through Hull York Medical School, York, UK.

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    RCT reg number 85268059.

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