Chest
Clinical InvestigationsDevelopment and Validation of the Cystic Fibrosis Questionnaire in the United States: A Health-Related Quality-of-Life Measure for Cystic Fibrosis
Section snippets
Participants
Participants were 212 adolescents and adults with a confirmed diagnosis of CF, ranging in age from 14 to 53 years. The mean age of participants was 23.0 years (SD, 8.1), and a similar number of male (49%) and female (51%) patients were enrolled. Disease severity was classified using the Knudson equations25 for FEV1 percentage of predicted. A wide range of disease severity was documented, with FEV1 percentage of predicted scores ranging from 17 to 130%. FEV1 percentage of predicted was missing
Procedures
To obtain a geographically representative sample, participants were recruited from 18 CF centers across the United States. Written informed consent and assent was obtained from all participants according to the procedures specified by the relevant institutional review boards. Patients were enrolled in this study during a routine clinic visit that was not associated with an acute illness or pulmonary exacerbation. All of the measures, including the CFQ, were administered prior to a physical
CFQ-Teen/Adult
The CFQ-teen/adult measure9 evaluated in this study consisted of 44 items across 12 scales (Table 1). Response choices generally included ratings of frequency and difficulty on a 4-point scale (1 = always to 4 = never; 1 = a lot of difficulty to 4 = no difficulty) or true/false responses (1 = very true to 4 = very false). Scores were standardized on a 0- to 100-point scale, with higher scores representing better quality of life.
SF-36
The SF-36 is a brief, generic health status measure consisting of 36 questions that yield eight health status scales: physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional, and mental health.3 Items are rated with respect to the individual's experience over the past 7 days. Scores range from 0 to 100, with higher scores indicating better quality of life and functioning. The SF-36 has been shown to be both reliable and valid, with internal
Preliminary Tests of the French CFQ
To test the fit between the items and scales identified in the French CFQ, a multitrait analysis was conducted (revised Multitrait/Multi-item Analysis Program28). This analysis assessed the extent to which items correlated with their hypothesized scale vs a competing scale. Psychometric guidelines suggest that item-to-scale correlations should be ≥ 0.40 with the intended scale and should correlate much lower with competing scales, after accounting for the SE of measure (item discriminant
Item-Level Analyses of the English CFQ
Two types of item-level analyses were conducted on the US national validation data. First, items were subjected to a multitrait analysis (revised Multitrait/Multi-item Analysis Program28) to evaluate item-to-scale relationships.30 Next, floor and ceiling effects were identified for each scale.
As can be seen in Table 2, a large percentage of items correlated highly with their intended scale; 95% of the item-scale correlations (corrected for overlap) were ≥ 0.40. In addition, 83% of the items
Scale-Level Reliability
Two scale-level analyses were conducted: (1) calculations of the internal consistency or reliability of each scale, and (2) test-retest reliability. First, scale-level reliability was calculated using Cronbach α. As can be seen in Table 3, the reliability coefficients ranged from r = 0.18 to 0.94, with a majority of the coefficients > 0.70. Only two domains fell below that cutoff: the Cronbach α for digestion was 0.67 and for treatment burden was 0.18.
Test-retest reliability was calculated on a
Construct Validity
Several hypotheses were tested to establish the validity of the CFQ. First, because CF is a deteriorating medical condition, a strong correlation was expected between age and CFQ scores, with higher HRQOL reported by adolescents vs adults. This hypothesis was supported with inverse relationships found between age and the physical, role, vitality, emotion, social, eating, health perceptions, and respiratory scales (rs = − 0.17 to − 0.36, p < 0.05). Next, respondents were classified into three
Convergent and Discriminant Validity With the SF-36
Convergent validity was tested by examining correlations between similar domains on the CFQ and SF-36. Strong associations were found between the CFQ and SF-36 on the following domains: physical (r = 0.81, p < 0.01), health perceptions/general health (r = 0.79, p < 0.01), vitality (r = 0.84, p < 0.01), role/role-physical (r = 0.73, p < 0.01), emotional functioning/mental health (r= 0.74, p < 0.01), and social (r = 0.57, p < 0.01). In contrast, discriminant validity was assessed by examining
Discussion
Results of this national study at 18 CF centers across the United States indicated that the CFQ is a reliable and valid measure of HRQOL for adolescents and adults with CF. In terms of both internal consistency coefficients and relationship to lung function, it is similar if not stronger than psychometric data presented for the American version of the St. George's Respiratory Questionnaire.31 Analysis of the item-scale relationships demonstrated support for the conceptual underpinnings of the
ACKNOWLEDGEMENT
We would like to extend our deepest appreciation to the adolescents and adults with CF who participated in this study, as well as the nurses and research coordinators at the 18 CF centers across the United States who recruited participants and collected the data: Memorial Miller Children's Hospital (Orange County, CA), Denver Children's Hospital (Denver, CO), Children's National Medical Center (Washington, DC), University of Florida Cystic Fibrosis Center (Gainesville, FL), Children's Memorial
References (46)
- et al.
Measuring treatment impact: a review of patient-reported outcomes and other efficacy endpoints in approved product labels
Control Clin Trials
(2004) - et al.
Outcome measures for clinical trials in cystic fibrosis
J Pediatr
(1994) - et al.
Impact of recent pulmonary exacerbations on quality of life in patients with cystic fibrosis
Chest
(2002) - et al.
American translation, modification, and validation of the St. George's Respiratory Questionnaire
Clin Ther
(2000) The minimal important difference: who's to say what is important?
J Clin Epidemiol
(1996)Introduction
(1996)- et al.
Measuring quality of life in asthma
Am Rev Respir Dis
(1993) - et al.
The MOS 36-item short-form health survey: conceptual framework and item selection
Med Care
(1992) Measurement of quality of life in cystic fibrosis
Curr Opin Pulm Med
(1998)- et al.
Toward consistency in cost-utility analyses: using national measures to create condition-specific values
Med Care
(1998)
Health outcome models for policy analysis
Health Psychol
Health economic benefits and quality of life during improved glycemic control in patients with type 2 diabetes mellitus: a randomized, controlled, double-blind trial
JAMA
The European Organization for Research and Treatment of Cancer QLQ-C30: a quality-of-life instrument for use in international clinical trials in oncology
J Natl Cancer Inst
The Cystic Fibrosis Questionnaire (CFQ): user's manual
Advances in cystic fibrosis gene therapy
Curr Opin Pulm Med
Intermittent administration of inhaled tobramycin in patients with cystic fibrosis
N Engl J Med
Effects of tobramycin solution for inhalation on global ratings of quality of life in patients with cystic fibrosis and Pseudomonas aeruginosa infection
Pediatr Pulmonol
NHLBI Workshop summary: clinical behavioral aspects of cystic fibrosis; directions for future work
Am Rev Respir Dis
Development of a disease specific health related quality of life measure for adults and adolescents with cystic fibrosis
Thorax
The Quality of Well-being Scale
Med Care
Measurement of quality of well-being in a child and adolescent cystic fibrosis population
Med Care
Quality of life as a treatment outcome in patients with cystic fibrosis
Pharmacotherapy
Quality of life in cystic fibrosis
Pharmacoeconomics
Cited by (390)
When chronicity meets cyclicity: The cultivation of embodied knowledge and selfhood by cis-gender women with cystic fibrosis
2024, SSM - Qualitative Research in HealthMobile health platform for self-management of pediatric cystic fibrosis: Impact on patient-centered care outcomes
2023, Journal of Cystic Fibrosis
Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).
This study was funded in part by the Cystic Fibrosis Foundation and Genentech, Inc.