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Minimal Erythema Dose (MED) Testing
Published on: May 28, 2013
The minimally important difference of the Asthma Control Test
Michael Schatz1, Mark Kosinski, Aaron S Yarlas
1Department of Allergy, Kaiser Permanente Medical Center, San Diego, Calif. 92111, USA. michael.x.schatz@kp.org
The Journal of Allergy and Clinical Immunology
|September 22, 2009
Summary
A minimally important difference (MID) for the Asthma Control Test (ACT) was established. A 3-point change on the ACT indicates a meaningful improvement in asthma control for patients.
Area of Science:
- Pulmonary Medicine
- Clinical Assessment
- Asthma Research
Background:
- The Asthma Control Test (ACT) is a validated tool for assessing asthma control.
- A minimally important difference (MID) for the ACT has not been previously established.
Purpose of the Study:
- To determine the minimally important difference (MID) for the Asthma Control Test (ACT).
Main Methods:
- Utilized data from 4 independent adult asthma patient samples.
- Employed distributional methods (0.5 SD, 1 SEM, 2 SEM) and anchor-based methods.
- Anchor-based methods correlated ACT score changes with asthma severity, episode frequency, physician ratings, therapy changes, FEV1, medication use, and patient-defined outcomes.
Main Results:
- Distributional MID estimates ranged from 1.88 to 3.75 points.
- Anchor-based analyses showed mean ACT score differences between patient groups of 3.1 points.
- A 3-point ACT difference predicted a 76% increased risk of excess SABA use and a 33% increased risk of exacerbations.
Conclusions:
- The findings support a minimally important difference (MID) of 3 points for the Asthma Control Test (ACT).
- This 3-point MID provides a clinically relevant threshold for interpreting changes in asthma control.
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