Journal of Pediatric Psychology, Vol. 28, No. 8, 2003, pp. 535-546
© 2003 Society of Pediatric Psychology
Validation of a Disease-Specific Measure of Health-Related Quality of Life for Children with Cystic Fibrosis
1 Department of Clinical and Health Psychology, University of Florida, 2 Department of Psychology, University of Miami
All correspondence concerning this article should be addressed to Avani Modi, Department of Clinical and Health Psychology, University of Florida, 101 South Newell Dr. (Rm. 3151), PO Box 100165, Gainesville, Florida 32610. E-mail: amodi{at}hp.ufl.edu.
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Abstract |
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Objective The purpose of the current study was to evaluate the psychometric properties of the Cystic Fibrosis Questionnaire (CFQ)–Child version, a disease-specific health-related quality of life (HRQOL) measure for children with cystic fibrosis (CF). Method The CFQ was administered to 84 children with CF, ranging in age from 7 to 13 years, and their parents. Results Multitrait analyses indicated that a majority of items on the CFQ-Child correlated more highly with their hypothesized scale than a competing scale. Internal consistency coefficients were acceptable for all scales (Cronbach's
= .60–.76), with the exception of treatment
burden (Cronbach's = .44). Results also suggested strong convergence
between child and parent-proxy reports on several scales of the CFQ.
Conclusion Results demonstrated that the CFQ-Child is a reliable and
valid measure of HRQOL for children with CF. Key words: health-related quality of life; children; Cystic Fibrosis; validation.
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Introduction |
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Cystic fibrosis (CF) is the most common fatal, autosomal recessive disorder of Caucasian populations. The incidence is 1 in 3,400 live births in the United States (Kosorok, Wei, & Farrell, 1996
), and it is estimated that approximately 10 million
individuals are carriers of the recessive gene worldwide
(Cystic Fibrosis Foundation [CFF],
2002). CF is a complex, progressive disease that affects the
exocrine glands of major organs, including those of the respiratory,
digestive, pancreas, liver, kidney, and reproductive systems. Treatment of the
disease involves a multicomponent regimen, including airway clearance
techniques, aerosol medications, inhalers, pancreatic enzymes, increased
calorie intake, and antibiotics
(Orenstein, Rosenstein, & Stern,
2000). These treatments are complex and time-consuming and must be
performed several times each day
(Quittner, Opipari, Regoli, Jacobsen,
& Eigen, 1992).
Life expectancy for individuals with CF has increased dramatically in the
last few decades. Twenty years ago, individuals with CF survived into
adolescence, but today earlier diagnosis and more aggressive treatments have
extended life expectancy into adulthood. Currently, the median life span for
individuals with CF is approximately 33 years
(CFF, 2002). However, it is
estimated that the median life expectancy for children born in 1990 is
approximately 40 years. Although life span has increased substantially, the
"quality" of these additional years has not been assessed.
The measurement of health-related quality of life (HRQOL) has received
considerable attention over the past 20 years. Although early on there was no
consensus about the definition of the construct
(Aaronson, 1992), significant
progress has been made recently in defining and measuring HRQOL. Over 50 years
ago, the World Health Organization (WHO,
1947) defined health as "a state of complete physical and
social well being, not just the absence of the disease." This definition
identified key dimensions of health that should be included, such as physical,
social, and psychological domains. Identification of these domains expanded
the construct of HRQOL and led to a set of principles which guided its
measurement (Spieth & Harris,
1996). A widely accepted definition of HRQOL specifies that it (a)
is a multidimensional construct that includes the core dimensions of physical
functioning and symptoms, psychological functioning, occupational functioning,
and social functioning (Schipper, Clinch,
& Olweny, 1996); (b) is patient centered rather than reliant
on the physician's view; and (c) reflects the individual's subjective
evaluation of his/her own functioning and well-being
(Quittner, 1998). The purpose
of the current study was to evaluate the psychometric properties of a new,
disease-specific measure of HRQOL for children with CF.
Why is it important to measure HRQOL in patients with CF? First, HRQOL
measures have the potential to describe health status in a meaningful way to
health care professionals and patients and their families
(Abbott, Webb, & Dodd,
1997). A traditional health outcome measure, such as pulmonary
functioning, which is the primary biological indicator of health status in
patients with CF, uses a single number to assess health. Pulmonary functioning
measures provide an estimate of current lung function, which may not
correspond to the patient's perception of illness severity. In contrast, HRQOL
measures provide a more comprehensive assessment of how this disease affects
patients' daily lives in several areas of functioning, including physical,
emotional, and social. Thus, HRQOL measures may be used to complement existing
clinical measures and provide health care professionals with a more thorough
assessment of functioning (Abbott et al.,
1997).
Second, HRQOL measures are useful for evaluating the impact of new
treatments on individuals with CF. With the advent of new medications and
treatments, measures of HRQOL enable us to assess the effectiveness of these
treatments in several areas of functioning. New drug therapies, such as
recombinant human deoxyribonuclease (rhDNase) and inhaled antibiotics, have
been evaluated in safety and efficacy trials and have demonstrated modest
improvements in pulmonary function and improved perception of HRQOL
(Fuchs et al., 1994;
Ramsey et al., 1993).
Similarly, in a recent study examining the effects on HRQOL of a tobramycin
solution for inhalation, researchers found that patients or parents of
children with CF in the treatment arm reported higher HRQOL on a global rating
question compared with control patients
(Quittner & Buu, 2002).
Although the results of these studies are promising, the use of ad hoc
questions, rather than standardized, well-validated HRQOL measurements, limits
our understanding of the impact of these treatments on other important areas
of functioning (e.g., social, emotional, vitality).
Third, measurement of HRQOL may have an impact on adherence to complex
medical regimens (Quittner,
1998). Individuals with CF are prescribed several time-consuming
treatments, which must be performed each day in order to prevent lung
infections and irreversible lung damage. Several studies have indicated that
rates of adherence are generally low
(Anthony, Paxton, Bines, & Phelan,
1999; Passero, Remor, &
Salomon, 1981; Quittner,
Drotar, et al., 2000), leading to a variety of negative health
consequences, such as increased hospitalizations, emergence of resistant
bacteria and viruses, missed days at school and work, and higher health care
costs. If patients perceive that a medication is effective and improves their
daily functioning, they are more likely to adhere to the regimen
(Bernstein, Kleinman, Barker, Revicki,
& Green, 2002). In conjunction with other health outcome data,
HRQOL measures can provide individuals with information about how prescribed
treatments are positively affecting various aspects of their lives
(Quittner, Davis, & Modi,
2003).
Finally, HRQOL data can inform economic planning and decision making
(Kaplan, 1989;
Torrance, 1987). Many of the
drug and airway clearance therapies for CF, such as rhDNase and the
ThAIRapy(r) Vest (Advanced Respiratory, St. Paul, Minnesota), are quite
expensive, ranging from $17,000 to $20,000. These treatments should be
evaluated for their efficacy in terms of their impact on a broad range of
outcomes, including physical, psychological, and social. This information is
critical in deciding how to distribute and spend health care dollars
associated with complex, chronic illnesses such as CF
(Kaplan, 1989).
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Measurement of HRQOL in Children with Cystic Fibrosis |
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One significant limitation of current HRQOL research is the lack of measures for children and adolescents (Landgraf, Abetz, & Ware, 1996
; Varni, Seid, & Rode,
1999). HRQOL measures designed for children should be
developmentally appropriate and assess daily functioning in contexts that are
relevant for children, such as school and community. Prior studies of HRQOL in
children with CF relied on generic measures, such as the Child Health
Questionnaire (CHQ) (Landgraf et al.,
1996) and PedsQLTM (Varni
et al., 1999). However, these measures have lacked the sensitivity
necessary to assess areas of functioning that are critically important for
children with CF, such as respiratory functioning and digestion. In addition,
the Quality of Well-Being scale, a utility measure, has been used with
adolescents and adults with CF with mixed results
(Czyzewski, Mariotto, Bartholomew,
LeCompte, & Sockrider, 1994;
Orenstein, Pattishall, Nixon, Ross, &
Kaplan, 1990). Note that utility measures were not originally
designed for use with children or adolescents. As a result, researchers in
France initiated the development of a disease-specific HRQOL measure for
children, adolescents/adults, and parents of children with CF, the Cystic
Fibrosis Questionnaire (CFQ) (Henry,
Aussage, Grosskopf, & Launois, 1996).
Cystic Fibrosis Questionnaire
French Model. In 1997, a CF-specific measure of HRQOL was
developed in France (Henry, Aussage,
Grosskopf, & Goehrs, 2003;
Henry et al., 1996). In the
first phase of testing, 20 items were generated for the CFQ-Child version.
Items were identified through extensive review of the literature and
interviews with experts in the field and individuals with CF and their
parents. Items on the questionnaires covered several key areas, including six
generic (e.g., physical functioning, psychological/emotional functioning,
energy/fatigue) and four disease-specific domains (e.g., eating disturbances,
body image, treatment constraints). Subsequent phases of testing utilized
Principal Axis Factoring and multitrait analyses to reduce the item pool for
the final questionnaire, as well as test its initial validity. Internal
consistency coefficients ranged from .46 to .71 for the CFQ-Child
(Henry et al., 1998).
U.S. Model. First, a translation and linguistic validation
of the CFQ was performed in the United States
(Quittner, Sweeny, et al.,
2000) following international guidelines for the translation and
validation of HRQOL measures from one language to another (see
Quittner, Sweeny, et al.,
2000, for a complete description of this process).
Next, a national validation study of the English CFQ-Parent, CFQ-Child, and
CFQ-Teen/Adult was conducted at 18 different CF centers
(Quittner, Buu, Watrous, & Davis,
2000). Results from this study yielded good internal consistency
coefficients for most scales, with the exception of the Treatment Burden and
Social scales. One item was added to each scale to improve internal
consistency coefficients. Results also suggested that the measure could be
downwardly extended to younger children. In addition, two different true-false
scales were evaluated in the national validation study, with results
indicating that children had problems rating the middle of the continuum
(i.e., very false, somewhat false, and somewhat true to very
true). Therefore, a simpler true-false scale was adopted for the
CFQ-Child. In sum, because a number of changes were made to the CFQ-Child,
further psychometric testing of the instrument was needed.
The purpose of the current study was to assess the reliability and validity
of a new, disease-specific HRQOL measure for children with CF. Several
predictions were made regarding the psychometric properties of the instrument.
First, items were expected to correlate more strongly with their hypothesized
than competing scales. Second, internal consistency coefficients for the
scales were expected to be >.60, which is regarded as acceptable for newly
developed scales (Ware et al.,
1980). Third, in terms of predictive validity, significant
relationships were expected between the CFQ-Child scales and health status
(e.g., pulmonary functioning). Specifically, strong associations were expected
between physical domains (e.g., respiratory, physical, treatment burden) and
pulmonary functioning. Finally, convergence was expected between the parent
and child versions of the CFQ, particularly for the Physical, Treatment
Burden, Respiratory, Digestive, Body Image, and Eating scales.
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Method |
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Participants
Eighty-four participants and their parents were recruited as part of a larger study examining the effectiveness of three different airway clearance techniques for children, adolescents, and adults with CF (Accurso, 1999
). Participants
were recruited from 22 geographically representative CF centers across the
United States, comprising 4% of participants from the West, 24% from the
Midwest, 32% from the Northeast, 39% from the South, and 1% from Puerto Rico.
(No significant differences were found between participants from these regions
on pulmonary functioning and HRQOL scales, with the exception of the social
scale, suggesting that the groups were homogeneous.) Potential participants
and their parents were approached during routine clinic visits while waiting
for their appointments. Patients were included in the study if they met the following criteria: (a) a proven diagnosis of CF as evidenced by a positive sweat test or the presence of two known CF mutations; (b) age 7 to 13 years; (c) forced expiratory volume in one second (FEV1) greater than 45% predicted; and (d) willingness to participate and comply with study procedures. Participants were excluded from the study if they had been hospitalized for complications of CF or any respiratory exacerbations resulting in antibiotic treatments or were using investigational drugs.
The mean age of children was 9.5 years, ranging from 7 to 13 years of age.
Forty-eight percent of the participants were female (see
Table I). Illness severity, as
measured by FEV1, ranged from 53% to 124% predicted, with a
majority of children (88%) falling into the mild category (
70%
predicted).
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Procedure
Research coordinators completed specialized training in order to
standardize the study protocol across sites and to recruit and screen
participants, administer consent forms, and instruct or administer
questionnaires to both children and their parents. The protocol and consent
forms were approved by the institutional review board at each site.
The CFQ-Child version was administered by the research coordinator to all children. Parents of participants were asked to complete a demographics questionnaire and the CFQ-Parent version, a proxy measure of HRQOL for children with CF. After completion of both versions of the CFQ, pulmonary functioning tests and physical exams were conducted to assess health status.
Measures
Cystic Fibrosis Questionnaire–Child Version. The
CFQ-Child is a disease-specific HRQOL measure for children with CF between the
ages of 6 and 13 (Quittner, Buu, et al.,
2000). Two versions of the CFQ-Child were established: an
interviewer-administered version for children 6–11 years of age and a
self-report version for 12–13 year olds. The CFQ-Child is a 33-item
instrument that assesses multiple domains of HRQOL. This questionnaire
includes three broad domains of HRQOL, including Physical Symptoms (6 items),
Emotional Functioning (8 items), and Social Functioning (5 items). The
CFQ-Child also assesses five domains specific to CF, which include Body Image
(3 items), Eating Disturbances (3 items), Treatment Burden (3 items),
Respiratory Symptoms (4 items), and Digestive Symptoms (1 item). Seventeen
items required a true-false rating on a 4-point scale ranging from not at
all true to very true. Sixteen items required a frequency
response ranging from always to never on a 4-point scale.
Children were presented with true-false ratings on an orange card and with
frequency ratings on a blue card. They were trained to use the response scales
with two practice items using the colored rating cards. The CFQ-Child took
approximately 15 minutes to complete. Raw scores for each of the eight scales
were converted into standardized scores (0–100), with higher scores
representing better HRQOL.
Cystic Fibrosis Questionnaire–Parent Version. The
CFQ-Parent is a measure of the parent's report of their child's HRQOL for
children aged 6 to13 (Henry et al.,
2003; Quittner, Buu, et al.,
2000). It is a 43-item self-report measure that assesses four
broad domains: Physical Symptoms (9 items), Emotional Functioning (5 items),
Vitality (5 items), and School Functioning (3 items); and seven CF-specific
domains: Eating Disturbances (3 items), Body Image (3 items), Treatment Burden
(2 items), Respiratory Symptoms (6 items), Digestive Symptoms (3 items), and
Weight (1 item), along with an overall Health Perception scale (3 items). The
CFQ-Parent took approximately 15–20 minutes to complete. Raw scores were
converted into standardized scores (0–100) for each of the 11 scales,
with higher scores indicating better HRQOL.
Health Status/Spirometry. Pulmonary function tests are the
gold standard for measuring respiratory functioning and lung damage for
individuals with CF. Specifically, FEV1 % predicted is the primary
biological indicator of health status, using the Knudson equations for age,
sex, and weight (Knudson, Slatin,
Lebowitz, & Burrows, 1976). Illness severity ratings are based
on established cutoffs for mild ( 70%), moderate (40–69%), and
severe (
39%) disease (Taussig,
1995).
Statistical Analyses
Descriptive statistics (means and standard deviations) were used to
characterize the demographic variables. To conduct item-level analyses, items
were subjected to a multitrait analysis (MAP-R program;
Ware, Harris, Gandek, Rogers, & Reese,
1997). Item-internal consistency was evaluated by correlating each
item with its own scale, corrected for overlap. Item-discriminant validity was
assessed by determining the percentage of items that correlated higher with
their hypothesized scale than a competing scale. This was computed for each of
the eight CFQ-Child scales. Furthermore, the range of item responses was
assessed by observing the percentage of respondents who reported the maximum
(ceiling effects) and minimum (floor effects) possible responses. Ceiling and
floor effects of > 20% were considered significant
(McHorney, Ware, Lu, & Sherbourne,
1994).
For scale-level analyses, internal consistencies were calculated using
Cronbach coefficients. Although coefficients of r = .70 are
recommended to compare groups (Nunnally
& Bernstein, 1994), Ware and colleagues
(1980) have suggested that
alpha coefficients .60 are considered acceptable for newly developed
scales.
To examine construct validity, Pearson product moment correlation coefficients were calculated to determine the relationship between health status (FEV1 % predicted) and CFQ-Child scaled scores (predictive validity). Paired correlations were used to determine the convergence of parent and child report of the child's HRQOL. Next, Student t tests were conducted to examine gender differences in the child's HRQOL. Finally, Pearson correlations were conducted between CFQ-Child scores and child's age.
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Results |
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Item-Level Analyses
Multitrait analyses indicated that a majority (56%) of the items on the CFQ-Child correlated more strongly with their hypothesized than competing scales, using Ware's criteria of .40 or higher as a scaling success (Ware et al., 1980
) (see
Table II). Item-to-scale
correlations were low for several items on the Emotion, Body Image, Social,
and Treatment Burden scales. At the scale level, scaling successes ranged from
86% for the Emotion, Social, and Body Image scales to 100% for the Eating
scale.
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Minimal floor effects were found for the CFQ-Child scales (0–2%). Ceiling effects across the eight CFQ-Child scales were generally minimal. However, a tendency to endorse higher HRQOL scores was observed for the Eating (51%), Digestive (46%), and Body Image (40%) scales.
Scale-Level Analyses
Internal consistency coefficients are presented in
Table III. Seven of the eight
CFQ-Child scales exceeded the minimum alpha coefficients of .60 for
reliability. These reliability coefficients represent an improvement over the
national validation study. The alpha coefficient for the treatment burden
scale was .44, suggesting low internal consistency. In order to assess whether
younger children could reliably complete the CFQ-Child, internal consistencies
for the CFQ-Child scales were also computed separately for younger (7–8
year olds) and older children (9–13 year olds) in the sample. There was
no evidence that younger children were less reliable in responding to the CFQ
than older children. Cronbach's ranged from .46 to .87 for younger
children, and from .43 to .64 for older children.
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Construct Validity
Predictive Validity. Correlations between health status, as
measured by pulmonary functioning (FEV1 % predicted), and the
CFQ-Child scales were conducted. Associations between pulmonary functioning
and CFQ scores were low due to restricted range of disease severity
(r = .01–.18). No children in this sample were severely ill and
only 12% were classified as moderately ill.
Convergent Validity. To examine convergence between parent-child dyads, paired correlations between the CFQ-Child and CFQ-Parent were calculated. Significant agreement was found for the Body Image (r = .34, p < .01), Eating (r = .37, p < .01), Treatment Burden (r = .22, p < .05), Digestion (r = .24, p < .05), and Respiratory scales (r = .32, p < .01). Despite the generally good agreement between parent and child reports, some differences were noted in their scores. Paired t tests were also conducted, which indicated that children reported lower HRQOL than their parents on the following scales: Physical, t(79) = –4.3, p < .001; Emotion, t(79) = –3.2, p < .01; and Digestion, t(79) = –3.0, p < .01 (see Table IV). Conversely, parents reported lower HRQOL for their children on the scales for Treatment Burden, t (79) = 9.8, p < .001; Body Image, t(79) = 2.1, p < .05; and Respiratory, t(78) = 2.2, p < .05.
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Gender and Age Differences
T tests were used to evaluate potential differences between males
and females on each of the eight CFQ-Child scales. A significant difference
between males and females was found on the respiratory scale, with females
scoring lower, t(82) = 2.1, p < .05. A post hoc analysis
was conducted to examine differences in pulmonary functioning for males and
females. Females had a mean FEV1 of 92.1% predicted and males had a
mean FEV1 % predicted of 92.3, indicating no substantial difference
in pulmonary functioning. Similarly, few significant associations were found
between CFQ-Child scores and age, with the exception of the Digestion scale
(r = .23, p < .05). Older children reported higher HRQOL
scores on the Digestion scale than younger children.
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Discussion |
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The overall purpose of this study was to evaluate the reliability and validity of an HRQOL instrument for children with CF. The CFQ-Child is a developmentally appropriate, disease-specific HRQOL measure that was designed to account for the multisystem nature of the disease and provide health care professionals with a precise and sensitive measure of daily functioning (Quittner, Buu, et al., 2000
).
In terms of item-level analyses, a majority of the items demonstrated
adequate item-internal and item-discriminant validity. This suggests that the
CFQ-Child exhibits both content and discriminant validity. Items on the
CFQ-Child were also able to elicit a range of responses from the positive to
the negative end of the scale, with little pooling at the extreme ends.
Negligible floor effects were found, suggesting that the instrument is valid
for CF patients experiencing significant health problems and thus potentially
low HRQOL. Ceiling effects were noted for three scales (eating, digestive, and
body image), indicating that respondents tended to endorse higher ratings of
HRQOL on these scales. However, in comparison with generic HRQOL measures for
children, such as the widely used CHQ and PedsQLTM, these ceiling effects
were minimal. Note that substantial ceiling effects have been found on one
third of the scales on the CHQ across several chronic disease groups,
including asthma, epilepsy, and juvenile rheumatoid arthritis
(Landgraf et al., 1996).
Internal consistency coefficients indicated that this version of the CFQ is reliable. This may be partly attributable to the adoption of a simpler true-false scale for children. Only the Social and Treatment Burden scales demonstrated low reliability. As a result, one item was revised in the Treatment Burden scale and one item was added to the Social scale to increase their reliability. These additional items will be tested in subsequent studies of the CFQ.
The downward extension of the CFQ-Child appeared to be successful. Internal consistency coefficients for the younger age group (7–8 years) were as high as those for the older group, indicating that younger children can reliably complete the CFQ-Child measure. Alpha coefficients for the older sample were slightly lower than those for the younger sample, which may be explained by the the older children's greater tendency to respond in a socially desirable manner, particularly in the interviewer-administered version. A self-report version of the CFQ-Child was created for 12–13 year olds in order to reduce these problems and will continue to be evaluated in future studies.
The relationship between health status variables and HRQOL was also
evaluated in this study. No associations were found between pulmonary
functioning and CFQ scores. This was likely due to the restricted range of
disease severity in younger children with CF. It is important to note that
inclusion criteria for the larger airway clearance study involved recruiting
children with FEV1 > 45% predicted, thus excluding children who
were severely ill. Average pulmonary functioning reported for the larger
national validation study was similar to the one reported here, indicating
that the sample recruited for this study was typical with respect to pulmonary
functioning for this age group (Quittner,
Buu, et al., 2000). The CFQ has been found to discriminate between
levels of disease severity in adolescent and adult populations, for whom there
is a wider range of pulmonary functioning
(Modi, Quittner, Davis, & Buu,
2002; Quittner, Buu, et al.,
2000). A recent study examining HRQOL in children with CF with
greater disease severity (e.g., children hospitalized for pulmonary
exacerbations) yielded substantially lower mean values on the CFQ
(Quittner, Stack, Modi, & Davis,
2002), indicating that the measure is sensitive to changes in
pulmonary functioning.
Another important issue in HRQOL research is the extent to which parents
and children agree on the affected child's HRQOL. There have been mixed
results in the literature regarding the importance of child versus parentproxy
reports of HRQOL. Prior research has questioned the validity and utility of
parent-proxy measures of HRQOL, since the parent's own emotional functioning
may affect the ratings of the child's HRQOL
(Vance, Morse, Jenney, & Eiser,
2001). However, the parent's report of the child's HRQOL is an
important method for identifying changes in health status that children may be
less aware of, such as increased symptoms or changes in daily functioning.
More recently, there has been an impetus to measure HRQOL by asking children
themselves about the impact of the illness on their daily life. This is a
critical perspective that, in conjunction with the parents' views, may more
effectively guide health care professionals in their treatment planning or
evaluation of behavioral interventions
(Quittner, Drotar, et al.,
2000).
In the current study, results indicated strong convergence between parents
(primarily mothers) and their children on the Body Image, Eating, Treatment
Burden, Digestive, and Respiratory domains. No significant associations were
found for the Physical and Emotional functioning domains. Parents rated the
Treatment Burden scale lower in comparison with their children's reports,
which may reflect the parents' view that the treatment regimen for CF is
burdensome for them. In contrast, children reported lower HRQOL on the Emotion
scale in comparison with parents. This finding may suggest that young children
have difficulty expressing their emotions directly to their parents. Measures
of HRQOL in other populations have also found higher patient/proxy concordance
for observable domains, such as physical functioning, and lower agreement
between children and their parents on emotional and social functioning
(Landgraf et al., 1996;
Verrips, Vogels, den Ouden, Paneth, &
Verloove-Vanhorick, 2000). In contrast, ratings of internalizing
problems may require the child to verbally report his/her feelings. Thus,
administering an HRQOL measure such as the CFQ-Child can provide the health
care team with the child's perspective on his/her emotional and social
functioning.
In terms of gender differences in HRQOL, epidemiological studies have
indicated that female patients with CF have a significantly poorer prognosis
and shorter life span than age-matched males. Generally, females with CF have
a more rapid decline in pulmonary functioning each year beginning soon after
puberty, which decreases their median survival age by approximately 4 years in
comparison with males (Davis,
1999; O'Connor et al.,
2002). Although several reasons for this gender difference have
been explored (e.g., nutritional status, airway microbiology), this
"gender gap" in survival has not yet been explained. Differential
patterns in HRQOL might shed light on the underlying causes of this gender
difference. In the current study, females reported significantly lower on the
Respiratory HRQOL scale than males. One explanation for these results is that
the CFQ-Child may be sensitive to early changes in pulmonary functioning, such
as increased coughing and wheezing, that may not be detected in a standard
pulmonary functioning test.
Despite the generally strong psychometric findings of this study, several limitations were noted. First, the sample size was relatively small and it is possible that stronger evidence of reliability and convergent validity might have been found with a larger sample size and increased power. In addition, a substantial proportion of items did not meet the criteria for item-level scaling success. Although many of these items were close to meeting the .40 standard, problems were identified for items on the Emotion, Social, and Treatment Burden scales. Additional items were revised or added to these scales. Moderate ceiling effects were found for the Body Image, Eating, and Digestive scales; however, the restricted range of disease severity in this sample may have contributed to these effects.
This new, disease-specific HRQOL measure for CF has wide applicability for
basic research, as well as for behavioral and pharmacological intervention
trials. There is an increasing focus on international drug trials, which
require validated HRQOL measures in several languages. The CFQ has now been
translated into German, Dutch, Portuguese, Spanish, Italian, and Greek. It has
also been used in several national studies to examine the impact of
antibiotics and airway clearance techniques on HRQOL
(Modi et al., 2001;
Quittner et al., 2002;
Saiman et al., in press).
HRQOL data, in conjunction with traditional health outcome measures such as
FEV1 % predicted, should further our understanding of the impact of
these treatments on the lives of patients with CF.
An important next step is to establish national norms for the CFQ. The CFQ
is now being added to the data collected annually for a national database in
the United States (Quittner, Modi, &
Davis, 2003). Establishment of a normative database would enable
health care professionals to compare an individual's reports of HRQOL with
those of other children who are similar in age, gender, and disease severity.
This information could be used to identify areas of risk for an individual
patient, document the benefits of new treatments, and inform medical decision
making. For example, if a child reported a decrease in physical and
respiratory functioning on the CFQ, physicians might choose to prescribe
rhDNase to increase respiratory functioning.
Another area for future research is determination of the minimal clinically
important difference (MCID) for the CFQ. The MCID is defined as "the
smallest difference in score, in the domain of interest, which patients
perceive as beneficial and which would mandate, in the absence of troublesome
side-effects and excessive cost, a change in the patient's management"
(Jaeschke, Singer, & Guyatt,
1989).
Finally, integrating the assessment of HRQOL into clinical practice has
considerable promise (Drotar et al.,
1998; Williams & Williams,
2003). For example, the CFQ could be completed during yearly
clinic visits to monitor functioning in a variety of domains. This process
could be computerized so that the health care team could examine the patients'
scores or HRQOL profile in real time, which may alert them to recent changes
in functioning. These data would enable health care providers to tailor
treatment needs to the individual and provide him /her with comprehensive
medical and psychological care. The CFQ measures and scoring manual may be
obtained free of charge by contacting the authors.
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Acknowledgments |
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This study was funded in part by the Cystic Fibrosis Foundation. We also acknowledge the support of our colleagues on the larger national Airway Clearance Study, Dr. Frank Accurso, Ms. Marci Sontag, and Ms. Joni Koenig. Finally, we extend our deepest appreciation to the children with cystic fibrosis and their families who participated in this study, as well as the nurses and research coordinators at the 22 CF centers across the United States who recruited participants and collected the data.
Received December 19, 2002; revision received February 12, 2003; accepted March 31, 2003
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