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Validation of a Pediatric Voice Quality-of-Life Instrument
The Pediatric Voice Outcome Survey
Christopher J. Hartnick, MD
Arch Otolaryngol Head Neck Surg. 2002;128:919-922.
ABSTRACT
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Objective To validate a parent proxy instrument to study the voice-related quality
of life (VR-QOL) for the pediatric population.
Methods The voice outcome survey (VOS) was administered to 108 caregivers of
children aged 2 to 18 years, who either had a tracheotomy or had achieved
surgical decannulation. The VOS was altered so that each item was addressed
to the parent proxy as opposed to the child. A scoring paradigm was developed
to report the scores on a range of 0 to 100. Structural properties of the
instrument examined include validity, reliability, and principal component
analysis. The VOS was then revised to suit the results of this analysis.
Results The mean ± SD (range) score for the pediatric VOS was 49.8 ±
27.1 (0-100). Reliability analysis and principal component analysis supported
the reduction of 1 item from the final pediatric VOS. The revised instrument
demonstrated an overall Cronbach  value of .86. Substratification by
age revealed robust Cronbach values from ages 2 to 18 years. Construct
validity analysis also supported statistical significance (P = .004). Principal component analysis of the revised instrument supports
its internal structure and design.
Conclusions The pediatric VOS is a simple, short, health status instrument designed
to measure the VR-QOL in the pediatric population. Cross-sectional analysis
suggests that children and adolescents with tracheotomies have a poorer VR-QOL
than do those who have achieved decannulation.
INTRODUCTION
THE APPLICATION of health-related quality-of-life (HR-QOL) instruments
to measure the health status of patients with voice disorders represents a
field of study that has only recently been developed. In this context, HR-QOL
can be defined as "the subjective and objective impact of dysfunction associated
with illness or injury, medical treatment, and health care policy."1 There have been several instruments designed to measure
this concept in the adult population. These populations have diverse pathologic
conditions, ranging from vocal cord paralysis to vocal fold nodules to spasmodic
dysphonia; the instruments designed have been used to assess the degree of
change after surgical remedy.2-4
When deciding on the choices of instruments to measure health status,
the first decision is whether to administer a "generic" or "specific" instrument.
There are a host of generic instruments designed to assess HR-QOL from a global
perspective.5-6 However, these
global instruments are not designed to capture the unique issues facing patients
with specific concerns generated by particular conditions such as voice disorders.
Global instruments are not likely to be sufficiently robust or sensitive to
the disease-specific issues and have been largely untested in their ability
to detect change over time.7
With regard to measuring HR-QOL for the pediatric population, this can
be accomplished by self-report or caregiver proxy. For children older than
5 years, there are general health status measures published according to a
self-report format for children.8 Age-appropriate
general health status measures have been successfully applied to the adolescent
population,9-10 to discrete areas
of pain management and symptoms scales, and to specific diseases.11-13 However, most assessments
of children and adolescents' HR-QOL continue to rely on parents as the source
of information.14-16
In their role as gatekeepers with the health care system, parents are thought
to have a better sense of the consequences of illness on their children's
lives. In addition to validity and reliability concerns, children and adolescents
are thought to lack the cognitive capacity to reflect on their health status
or to understand fully their illness or its implications on present and future
functioning.17-20
For the purposes of studying the population of children and adolescents with
voice concerns specific to congenital- or neonatal-acquired lesions necessitating
a tracheotomy, most of these children receive their tracheotomy before age
2 years. Moreover, most of those receiving surgical intervention aimed toward
decannulation are younger than 4 years. These 2 facts argue toward the use
of a parent proxy instrument for assessing the effect of pediatric voice disturbances
on the overall quality of life of the child.
MATERIALS AND METHODS
Parents and caregivers of children and adolescents who have undergone
tracheotomy were contacted via an active Web site that provides information,
counsel, and support to such families21 or
by direct mailing to families whose children had received a tracheotomy at
the Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio. The Web
site chosen (http://www.tracheostomy.com) is specifically designed
for families in which a child has received a tracheotomy. Currently, several
hundred families access this Web site as a source of information.21 The pediatric voice outcome survey (VOS) was administered
after obtaining permission for its use from its senior author (R. E. Gliklich,
MD). The VOS was altered to allow for parent proxy administration. The items
were therefore addressed to the health care proxy in lieu of addressing the
children or adolescents themselves. Prior to the beginning of the study, it
was reviewed by the institutional review board of the Cincinnati Children's
Hospital Medical Center and received approval. An introductory paragraph was
placed on the first page of the Web site for purposes of informed consent
and a link was established for the parent/primary caregiver to receive the
instrument itself. Then the parent/primary caregiver either completed the
instrument online and e-mailed the completed instrument to the primary investigator
(C.J.H.) or downloaded the instrument for completion and then sent the form
directly to the primary investigator. The completed forms were entered into
a Microsoft Access (Microsoft, Seattle, Wash) database, and analysis was performed
by linking the database to the SAS 8.1 software package (SAS Institute Inc,
Cary, NC).
RESULTS
Overall, 108 caregivers of children or adolescents requiring tracheotomies
or who had required tracheotomies in the past and have been decannulated participated
in the study and completed the instrument. Missing data were handled by assigning
"0" values as missed entry values. Overall, there was less than a 0.001% incidence
of missing data points. The population characteristics for the respondents
and their children are delineated in Table
1.
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Table 1. Population Characteristics
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A mean score was calculated using all the items included in the VOS.
Three items required score reversal to remain consistent with a scale whereby
low scores indicate a "poor" HR-QOL. The overall score was then fitted to
a scale ranging from 0 to 100.
The instrument's reliability was assessed by means of calculating Cronbach
values (this allows for the assessment of item-total correlations to measure
the impact of systematically deleted variables within the central construct).
A coefficient of greater than .65 was interpreted to be robust (>.55
was deemed acceptable).22 Principal component
and factor analysis was then performed to evaluate the internal structure
and the design of the instrument with reference to its application to the
pediatric population. While reliability analysis and factor analysis supported
the overall structure, they also suggested that 1 particular item (relating
to swallowing) within the instrument did not fit as well as the other items
within the overall schema (Figure 1).
Accordingly, this item was deleted from the instrument, and the instrument
was then reanalyzed for purposes of reliability and principal component analysis.
The results of both the initial and final analyses are given in Table 2 (see the "Comment" section). The values for the
revised pediatric VOS were then evaluated to assess the reliability of the
instrument for various subpopulations of children and adolescents according
to their age (Table 3). The revised
instrument with the 1 item deleted was then examined, and the overall mean
± SD (range) score was 49.8 ± 27.1 (0-100).
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Initial pediatric voice outcome survey (VOS). Revised and final pediatric
VOS does not include question 4.
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Table 2. Cronbach Values (Reliability) and Factor Analysis
Values for Overall Instrument With (Initial Pediatric VOS) and Without (Revised
Pediatric VOS) Item Regarding Swallowing*
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Table 3. Cronbach Values for Overall Instrument Documenting
Reliability Analysis for the Pediatric VOS as Substratified by Age*
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To assess the validity of the instrument, an evaluation of the instrument's
construct validity was performed (ie, the instrument's ability to identify
and demonstrate significant differences in subpopulations with regard to preconceived,
a priori hypotheses). The initial hypothesis evaluated was that for 2 discrete
populations of children and adolescents, those with tracheotomies (population
1) would experience vocal disturbances in a more significant and profound
way than those whose tracheotomies had been removed (population 2). A sample
size of 130 was chosen to be sufficiently robust to determine intergroup differences
based on 80% power to detect significant differences (P = .05), assuming medium effect size.23
Although the actual sample size was slightly smaller than that hypothesized,
a 2-tailed t test performed to compare the mean scores
(population 1, 39.4; population 2, 51.6) for these 2 populations demonstrated
statistical significance (P = .004).
COMMENT
The field of outcomes research with regard to vocal disturbances has
only recently begun to be explored. At present, most work has focused on the
impact of vocal disturbances on adult populations with a variety of disorders
before and after various treatments. Within the field of pediatric otolaryngology,
there are also a host of disorders in which the impact of a child's ability
to vocalize and to interact with his or her peers and community are of notable
importance. Examples of children and adolescents with disorders that coexist
with impaired ability to vocalize include those with vocal cord paralysis,
those with subglottic stenosis necessitating a tracheotomy, those with velopharyngeal
insufficiency, or those with gastroesophageal reflux disease and vocal cord
nodules. These examples represent only a small subset of pediatric conditions
in which pathological vocal alterations may affect the child and his or her
ability to interact and to develop appropriate communication skills in a meaningful
way.
A formal algorithm for assessing the pediatric voice has yet to be developed.
Any such examination of necessity includes a detailed history and physical
(obtained according to age by the caregiver or child, or a combination of
these two). Visualization of the airway is accomplished by flexible and rigid
endoscopy as appropriate; imaging studies (computed tomography or magnetic
resonance imaging) can be useful for initial evaluation of certain voice disorders
such as unexplained vocal cord paralysis. Other studies that are used at various
centers include stroboscopy, electroglottography, and ultrasonography. All
of these procedures are technician dependent, and the interpretation of these
examination findings varies inversely with the age of the child. Laboratory
tests are helpful in a small discrete population in whom the history and physical
examination findings are suggestive.
Functional assessment of the child's ability to vocalize may provide
invaluable supplementary information to the field of pediatric laryngology,
which at present lacks well-accepted objective parameters. While many of the
disorders that affect the pediatric airway require interventions that necessitate
a balance between establishing a patent airway and preserving an adequate
voice, the definition of what constitutes an adequate voice needs clarification.
Moreover, as more focus is placed on integrating functional outcomes regarding
vocal performance into comprehensive care regarding the pediatric airway,
novel strategies may be devised to allow for both goals to be more readily
accomplished. Finally, reporting of functional outcomes allows for an understandable
objective criteria to assess outcomes regarding one institution's results
or multi-institutional results; such information would be invaluable for caregivers
trying to make informed decisions regarding their children.
The present study draws on a defined population of children and adolescents
and their caregivers to validate a instrument to study voice-related quality
of life (VR-QOL). The result therefore is a validated instrument for children
and adolescents with tracheotomies aged 2 to 18 years. The next step in creating
a global pediatric VR-QOL instrument is to administer the instrument to otherwise
healthy pediatric subjects for analysis purposes. With regard to this specific
population, the VOS is a valid instrument, although reliability analysis suggests
that the 1 item describing pediatric swallowing issues does not provide information
that is unique and separate from the responses to the other 4 items. These
reliability data were obtained post hoc, and all the items in the original
VOS were used for initial application. Nevertheless, for this particular pediatric
population, the modified pediatric VOS is statistically more streamlined in
terms of congruent reliability. For other pediatric populations, the full
VOS might be appropriate.
The pediatric VOS is cross-sectional by design, and a longitudinal application
of this instrument is in progress to explore more fully the changes in VR-QOL
over time on a patient-by-patient basis. To give more meaning to the scores
generated by this instrument, further work needs to be done to establish normative
data for purposes of cross-population comparisons. Simultaneous application
of generic instruments measuring a child's overall HR-QOL and instruments
measuring the caregiver's HR-QOL and measure of caregiver burden would further
bolster the ease and breadth of interpretability of the pediatric VOS. Finally,
for the disorders that affect the pediatric airway while the child is still
relatively young, a parent proxy instrument remains valid. The pediatric VOS
has been validated for children and adolescents aged 2 to 18 years, but most
children in this study were younger than 5 years. Validation of a self-administered
instrument for older children would appear warranted for those who are more
cognizant of their situation.
In conclusion, the pediatric VOS represents a validated, brief instrument
to assess the VR-QOL in the pediatric population. It has been to shown to
discriminate between subpopulations to document that children and adolescents
with tracheotomies have a poorer VR-QOL than do those who have achieved decannulation.
AUTHOR INFORMATION
Accepted for publication January 9, 2002.
This study was presented at the annual meeting of the American Society
for Pediatric Otolaryngology, Boca Raton, Fla, May 13-14, 2002, and has received
first place for the Charles F. Ferguson Resident Research Award.
Corresponding author and reprints: Christopher J. Hartnick, MD, Harvard
Medical School, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary,
243 Charles St, Boston, MA 02114 (e-mail: christopher_hartnick{at}meei.harvard.edu).
From the Department of Otolaryngology, Massachusetts Eye and Ear Infirmary,
Boston.
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