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Original Research: CYSTIC FIBROSIS |

Determination of the Minimal Clinically Important Difference Scores for the Cystic Fibrosis Questionnaire-Revised Respiratory Symptom Scale in Two Populations of Patients With Cystic Fibrosis and Chronic Pseudomonas aeruginosa Airway Infection

Alexandra L. Quittner, PhD; Avani C. Modi, PhD; Claire Wainwright, MBBS, MD; Kelly Otto, MS; Jean Kirihara, BS; A. Bruce Montgomery, MD
Author and Funding Information

*From University of Miami (Dr. Quittner), Coral Gables, FL; Cincinnati Children's Hospital Medical Center and the University of Cincinnati (Dr. Modi), Cincinnati, OH; Royal Children's Hospital and University of Queensland (Dr. Wainwright), Brisbane, QLD, Australia; Kelly Otto Consulting (Ms. Otto), Seattle, WA; JKirihara Consulting Services (Ms. Kirihara), Seattle, WA; and Gilead Sciences Inc (Dr. Montgomery), Seattle, WA.

Correspondence to: Alexandra Quittner, PhD, University of Miami, 5665 Ponce de Leon Blvd, Coral Gables, FL 33146; e-mail: aquittner@miami.edu


Study 1-exacerbation was funded by Gilead Sciences, Inc and National Institutes of Health General Clinical Research Center grants M01 RR00043, M01 RR00046, M01 RR00064, M01 RR00082, M01 RR00188, M01 RR00400, and M01 RR000489. Study 2-stable was funded by Gilead Sciences, Inc; US Food and Drug Administration grant No. 1R01FD003016-01; and National Institutes of Health General Clinical Research Center grants M01 RR00034, M01 RR00037, M01 RR00039, M01 RR00042, M01 RR00043, M01 RR00046, M01 RR00064, M01 RR00065, M01 RR00069, M01 RR00070, M01 RR00082, M01 RR00188, M01 RR00400, M01 RR000489, M01 RR00750, M01 RR00827, M01 RR01066, M01 RR001070, M01 RR02172, M01 RR10710, M01 RR10733, and M01 RR023940.

Drs. Quittner and Modi were consultants for Corus Pharma (now Gilead Sciences, Inc). Dr. Wainwright was the principal clinical investigator for one of the studies described herein. Ms. Otto, Ms. Kirihara, and Dr. Montgomery were employees of Corus Pharma (now Gilead Sciences, Inc).

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).


© 2009 American College of Chest Physicians


Chest. 2009;135(6):1610-1618. doi:10.1378/chest.08-1190
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Background:  The Cystic Fibrosis Questionnaire-Revised (CFQ-R) is a validated patient-reported outcome (PRO) containing both generic scales and scales specific to cystic fibrosis (CF). The minimal clinically important difference (MCID) score for a PRO corresponds to the smallest clinically relevant change a patient can detect. MCID scores for the CFQ-R respiratory symptom (CFQ-R-Respiratory) scale were determined using data from two 28 day, open-label, tobramycin inhalation solution (TIS) studies in patients with CF and chronic Pseudomonas aeruginosa airway infection. At study enrollment, patients in the study 1-exacerbation had symptoms indicative of pulmonary exacerbation (n = 84; < 14 years of age, 31 patients; ≥ 14 years of age, 53 patients); patients in study 2-stable had stable respiratory symptoms (n = 140; < 14 years of age, 14 patients; ≥ 14 years, 126 patients).

Methods:  The anchor-based method utilized a global rating-of-change questionnaire (GRCQ) that assessed patients' perceptions of change in their respiratory symptoms after TIS treatment. The mean change from baseline CFQ-R-Respiratory scores were mapped onto the GRCQ to estimate the MCID. The two distribution-based methods were as follows: (1) 0.5 SD of mean change in CFQ-R-Respiratory scores (baseline to end of TIS treatment); and (2) 1 SEM for baseline CFQ-R-Respiratory scores. Triangulation of these three estimates defined the MCIDs.

Results:  MCID scores were larger for patients in study 1-exacerbation (8.5 points) than for those in study 2-stable (4.0 points), likely reflecting differences in patient disease status (exacerbation/stable) between these studies.

Conclusions:  Patient benefit from new and current CF therapies can be evaluated using changes in CFQ-R-Respiratory scores. Using the MCID provides a systematic way to interpret these changes, and facilitates the identification of CF treatments that improve both symptoms and physiologic variables, potentially leading to better treatment adherence and clinical outcomes.

Trial registration (study 1-exacerbation):  Australian-New Zealand Clinical Trials Registry Identifier: ACTRN 12605000602628

Trial registration (study 2-stable):  ClinicalTrials.gov Identifier: NCT00104520

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