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Development and Validation of the Neck Dissection Impairment Index
A Quality of Life Measure
Rodney J. Taylor, MD, MSPH;
Judith C. Chepeha, MScPT;
Theodoros N. Teknos, MD;
Carol R. Bradford, MD;
Pramod K. Sharma, MD;
Jeffrey E. Terrell, MD;
Norman D. Hogikyan, MD;
Gregory T. Wolf, MD;
Douglas B. Chepeha, MD, MSPH
Arch Otolaryngol Head Neck Surg. 2002;128:44-49.
ABSTRACT
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Objectives To validate a health-related quality-of-life (QOL) instrument for patients
following neck dissection and to identify the factors that affect QOL following
neck dissection.
Design Cross-sectional validation study.
Setting The outpatient clinic of a tertiary care cancer center.
Patients Convenience sample of 54 patients previously treated for head and neck
cancer who underwent a selective neck dissection or modified radical neck
dissection (64 total neck dissections). Patients had a minimum postoperative
convalescence of 11 months. Thirty-two underwent accessory nerve–sparing
modified radical neck dissection, and 32 underwent selective neck dissection.
Main Outcome Measure A 10-item, self-report instrument, the Neck Dissection Impairment Index
(NDII), was developed and validated. Reliability was evaluated with test-retest
correlation and internal consistency using the Cronbach  coefficient.
Convergent validity was assessed using the 36-Item Short-Form Health Survey
(SF-36) and the Constant Shoulder Scale, a shoulder function test. Multiple
variable regression was used to determine variables that most affected QOL
following neck dissection
Results The 10-item NDII test-retest correlation was 0.91 (P<.001)
with an internal consistency Cronbach coefficient of .95. The NDII
correlated with the Constant Shoulder Scale (r =
0.85, P<.001) and with the SF-36 physical functioning
(r = 0.50, P<.001) and
role–physical functioning (r = 0.60, P<.001) domains. Using multiple variable regression,
the variables that contributed most to QOL score were patient's age and weight,
radiation treatment, and neck dissection type.
Conclusions The NDII is a valid, reliable instrument for assessing neck dissection
impairment. Patient's age, weight, radiation treatment, and neck dissection
type were important factors that affect QOL following neck dissection.
INTRODUCTION
WE EVALUATED patients with head and neck cancer to assess the long-term
effects of neck dissection on quality of life (QOL) related to shoulder dysfunction.
Patients frequently have varying degrees of shoulder impairment following
neck dissection, which range from mild to profound dysfunction.1-4
What is not well established is whether the degree of shoulder impairment
observed has significant QOL implications in this population. Our objective
was to determine the specific complaints and difficulties that patients report
after neck dissection and to design a reliable and valid self-report instrument
that would enable us to assess the QOL impact related to neck dissection.
The shoulder syndrome, characterized by Nahum,5 is a constellation of symptoms that include shoulder
pain, limitations of abduction, and scapular winging. Depending on the extent
of the neck dissection, patients can have a variable amount of difficulty
with shoulder syndrome. Even after convalescence, the shoulder impairment
can be lasting and substantial enough to affect an individual's QOL through
changes in employment status, recreational pursuits, and personal independence.
When serious impairment occurs, major changes in lifestyle are necessary to
accommodate patients' limitations.6-8
To evaluate the factors that affect QOL after neck dissection, we developed
a self-administered questionnaire, the Neck Dissection Impairment Index (NDII).
The problems related to this population are unique and require investigation
specific to their issues.9 Standard psychometric
methods were used to evaluate the validity and reliability of the instrument.10-12 It was our goal to
develop a questionnaire that was reliable and easy to administer and that
would evaluate the difficulties patients have following neck dissection.
MATERIALS AND METHODS
STUDY DESIGN
We conducted a cross-sectional study to evaluate the factors that affect
patients following neck dissection procedures. Our intention was to design
and validate a self-administered survey questionnaire that measured patient's
QOL related to shoulder impairment.
On study entry, patients received the NDII and the Medical Outcomes
Study 36-Item Short-Form Health Survey (SF-36) following informed consent.
Permission to use the SF-36 was approved by the Medical Outcomes Trust. Subsequently,
each patient performed the Constant shoulder functional test after self-administration
of the 2 questionnaires. For patients who had undergone bilateral neck dissections,
each side was evaluated and scored separately with the NDII and the Constant
Shoulder Scale.
PATIENTS
There were 54 patients in the study group who had undergone a total
of 64 neck dissection procedures (10 patients received bilateral procedures).
A total of 32 accessory nerve–sparing modified radical neck dissections
(MRNDs) and 32 selective neck dissection (SND) procedures were performed in
this group. The mean ± SD age of the study population was 56.8 ±
11.7 years, and the mean weight was 73.5 ± 14.9 kg. Thirty-nine patients
were male; 15 were female; and the mean time elapsed from surgery was 33.7
months (range, 11-120 months). Tumors were found in the oral cavity in 10
patients; oropharynx, 23 patients; larynx or hypopharynx, 10 patients; other
sites, 8 patients; and unknown primary sites, 3 patients. Tumors were staged
according to the TNM staging system (according to the AJCC Cancer Staging Manual) as TX for 4 patients, T1 through T2 for 15 patients,
T3 through T4 for 35 patients, N0 for 30 patients, N1 for 10 patients, N2
for 23 patients, and N3 for 1 patient. Most patients received both surgery
and radiation therapy (87%), and squamous cell carcinoma was the most common
tumor type (92.5%).
For the development and validation of the questionnaire, patient inclusion
criteria were having previously untreated and diagnosed head and neck cancer
and concurrently requiring selective or modified neck dissection as part of
the management of head and neck cancer. Patients were excluded if they had
undergone surgery less than 11 months previously, reported any history of
unrelated neck or shoulder pathologic conditions, or had known recurrent disease
at the time of evaluation. Enrolled patients received their head and neck
cancer treatment at the Department of Otolaryngology, University of Michigan,
Ann Arbor, and were encountered on an outpatient basis during their routine
follow-up care. The University of Michigan's Institutional Review Board approved
study materials and methods.
THE NDII
Initial topics selected for the questionnaire were developed after a
review of the relevant literature concerning shoulder dysfunction after neck
dissection.1-8
Additional topics were selected after interviews with approximately 40 patients
in an outpatient setting who had previously undergone a neck dissection procedure.
Patients responded to open-ended questions that pertained to topics that included
(but were not limited to) neck and shoulder symptoms, limitations in activities
of daily living, occupational and leisure activities, and social and emotional
effects related to shoulder impairment. Survey items were refined by a panel
that consisted of otolaryngologists, physical therapists specializing in rehabilitation
of postsurgical oncology patients, and survey specialists from the University
of Michigan School of Public Health. Finally, the items were pilot-tested
on a group of 25 patients undergoing neck dissections to further evaluate
survey comprehension, content, and clarity. During patient piloting, it was
clear that patients who had undergone bilateral procedures could readily distinguish
between symptoms and limitations that emanated from one side vs the other.
Patient instructions designated that responses to each item be considered
"during the last 4 weeks." For each survey item, a Likert scale was used with
5 response options. Initially, the NDII contained 15 items; 10 items remained
after item reduction. Figure 1 shows
the 10 items (in summary form) that remained after validation. Scoring was
achieved by rating response items from 1 to 5, with 5 representing better
QOL related to neck dissection. Scores were then transformed to a 0 to 100–point
scale.
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Figure 1. Ten-item validated Neck Dissection
Impairment Index questions. Respondents answered "not at all," "a little bit,"
"a moderate amount," "quite a bit," or "a lot." Standardization for score
of 100: [(raw score - 10)/40] x 100.
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36-Item Short-Form Health Survey
The SF-36 is a validated and widely used general health QOL survey that
assesses 8 areas (domains) of general health.13-14
The 8 areas relate to physical functioning, role–physical functioning,
bodily pain, role–emotional, social functioning, mental health, vitality,
and general health perceptions. Each domain is scored from 0 to 100, with
higher scores representing better health QOL. We selected the SF-36 to establish
concurrent validity with the NDII because of the extensive use of the SF-36
across many patient groups as a general measurement of health-related QOL.
CONSTANT SHOULDER ASSESSMENT
The Constant Shoulder Scale was also selected to support criterion validity.
It is a validated clinical assessment of shoulder function that has established
utility and accuracy across all diseases that affect the shoulder. This validated,
widely used clinical test is an accurate and sensitive measure of shoulder
function, detecting subtle changes in shoulder function.15
It is a weighted test that combines patient symptom scores and objective measures
of active shoulder range of motion, combined internal rotation, combined external
rotation, and shoulder strength in the plane of the scapula. Scores range
from 0 to 100, with higher scores indicating better shoulder function. Demonstrating
a strong correlation between this functional measurement and a measure of
QOL will provide support that QOL is affected by shoulder function.
STATISTICAL METHODS
All patient data, including demographic information, survey data, and
disease information, were compiled in a relational database on a personal
computer. Data entries were checked and verified against the primary data.
All statistical procedures were performed using statistical software (SAS
version 6.12; SAS Institute Inc, Cary, NC). Both a principal components analysis
and an exploratory factor analysis with a varimax transformation were initially
performed on the NDII. Reliability was established in 2 manners: single-item
and total score test-retest correlation and internal consistency with Cronbach .
Both the factor analysis and the reliability measures were used to determine
item reduction. Items with less than 0.50 retest correlation were not considered
reliable and thus not included in the final index. Content and face validity
were confirmed with patient piloting and interviews, whereas discriminant
validity was evaluated by exploring correlation with SF-36 domains and the
Constant Shoulder Scale.
Multivariable regression analysis was used to model the dependent variables.
Univariate and stepwise regression analyses were used to facilitate selection
of variables. Preliminary analysis of variables included evaluation for the
presence of multicollinearity, such that candidate models contained no violations
of multicollinearity. Independent variables assessed included patient age,
time elapsed from surgery, tumor stage (T1-T2 or T3-T4), tumor site (oral
cavity, oropharynx, and hypopharynx and larynx), patient weight, radiation
therapy, handedness, and neck dissection type (SND or MRND).
RESULTS
THE NDII
Exploratory factor analysis with varimax transformation revealed 1 large
factor and 2 smaller factors; factors with eigenvalues less than 1 were not
considered. A 10-item factor that addressed physical abilities and activities
was identified as the main domain; a second factor without an apparent unifying
theme consisted of items relating to driving, appearance, and sleep. The third
factor had a 2-item cluster, which related to stress and QOL. Individual item
and factor eigenvalues are listed in Table
1. The 10-item factor was ultimately used for the final version
of the NDII.
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Table 1. Factor and Item Eigenvalue
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RELIABILITY
Both individual item and total score test-retest correlation were performed
using the Spearman log-rank correlation to assess reliability. Respondents
were asked to complete the questionnaire 5 days after initial entry; 87% of
patients who were retested completed the survey. Total score correlation was
0.91, whereas individual item correlation ranged from 0.41 to 1.00.
Internal consistency was determined using the Cronbach coefficient.
The initial 15-item survey had an overall coefficient of .94; however,
5 items had poor test-retest reliability coefficients or poor internal consistency
and therefore were omitted in the final 10-item version of the NDII. The omitted
items correspond to the items in the smaller factors 2 and 3. The remaining
10 items contained within factor 1 were used for further analysis. The 10-item
version had an overall internal consistency of .95.
VALIDITY
Convergent validity was evaluated using the Constant Shoulder Scale.
The mean (SD) Constant Shoulder Scale score for all patients was 70.7 (17.4)
(range, 38-100). Our hypothesis was that the NDII would have a high, positive
correlation with this instrument. The overall correlation between the 2 was
0.85 (P<.001). Correlating the NDII with the SF-36
domains that were hypothesized to correlate with it also tested convergent
validity. Specifically, we hypothesized that the role–physical, physical
functioning, and body pain domains would have good correlation with the NDII.
The SF-36 role–physical (r = 0.60, P<.001) and physical function domains (r
= 0.50, P<.001) had good correlation with the
NDII survey, whereas the body pain domain had relatively weak but significant
correlation (r = 0.32, P
= .005) (Table 2). The social
functioning and mental health SF-36 domains also exhibited good correlation
with the NDII.
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Table 2. NDII Validation Tests*
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NDII SCORES
Individual items from the 10-question NDII were scored from 1 to 5,
with 5 representing higher QOL responses. The total NDII score was then scaled
to a 100-point cumulative score. The overall mean ± SD score for all
patients was 67.8 ± 17.4 (range, 7.5-100.0). Figure 2 demonstrates mean scores (1 to 5) for each item question.
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Figure 2. Neck Dissection Impairment Index
(NDII) item component scores. Error bars indicates SDs.
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MULTIVARIABLE REGRESSION ANALYSIS
After validating the NDII, we used the data collected from the NDII
and SF-36 to determine the factors that best predicted long-term shoulder
QOL. We used the NDII and SF-36 as dependent variables for QOL in multivariable
regression analyses and factored in important treatment, clinical, and demographic
variables. When analyzing the SF-36, we evaluated total composite score, individual
domains, and summary scores from the physical component summary and mental
component summary. The best models for predicting QOL-related shoulder function
were obtained with the NDII as the dependent variable. This supports the NDII
as a useful disease-specific measure of shoulder-related QOL. No single domain
or summary score of the SF-36 could fit as good a model. Of the SF-36 domains
and summary scores, the physical component summary scale was the best QOL
predictor (R2 = 0.32, P<.001).
The best NDII model predicting shoulder-related QOL included the following
parameters: patient age in years (P = .12), weight
in kilograms (P<.001), neck dissection type (P = .14), and use of external beam radiation therapy (P = .04).
The final model equation was as follows:
NDII = 5.44 + 0.82 (Kilograms) - 13.45 (Radiation Therapy) + 0.30 (Age) - 6.43 (Neck Dissection Type).
Several factors led to the selection of this model. Of the candidate
models, this model had one of the best R2
values (0.44), had a well-matched Cp criterion, and was significant
(P<.001). The variables contained in this model
were each found in the best 1-, 2-, and 3-parameter models obtained with stepwise
multivariable regression analysis. Radiation was used on 87% of our sample
population. We evaluated whether including radiation therapy in the model
would serve as a confounder or surrogate for other clinical and demographic
factors, such as extent of disease or type of neck dissection performed. Therefore,
the issues of multicollinearity and bias of radiated versus nonradiated patients
within the other variables were carefully examined. We found no violations
of multicollinearity, and radiation therapy independently provided a substantial
magnitude to the overall model equation. This 4-variable model was chosen
over models with more variables because more variables did not appreciably
strengthen the model. To understand the magnitude of contribution of each
of the variables to the overall model, the following is an example of how
the model equation can be interpreted. In a 70-year-old, 70-kg patient, weight
would contribute nearly 55 points (0.82 x 70 kg) to the overall score
(maximum of 100 points), and age would contribute 21 points (0.30 x
70 years). However, the addition of radiation would decrease the overall score
by 13.45 points, and MRND would decrease the score by 6.43 points.
COMMENT
In this study we were able to design and validate a QOL-specific instrument
in patients who had undergone neck dissection and correlate long-term impairment
with the Constant Shoulder Scale, a validated shoulder function assessment.
Excellent reliability and validity of the NDII was demonstrated by test-retest
correlation (r = 0.91), internal consistency (r = 0.95), and good convergent validity with the Constant
Shoulder Scale (r = 0.85) and SF-36 domains (role–physical
and physical functioning domains). Furthermore, when the SF-36 was modeled
as the dependent variable, no multivariable regression model using the SF-36,
or any of its domains and component scales, was as good as the NDII.
The variables that most affected long-term shoulder impairment were
identified through multiple variable regression analysis. These factors included
the type of neck dissection performed (SND vs MRND), treatment with external
beam radiation, patient's age, and patient's weight.
The type of neck dissection performed was an important factor; patients
treated with MRND had worse NDII scores than those treated with SND. Other
studies have evaluated shoulder function following different types of neck
dissection procedures. Remmler et al8 serially
compared accessory nerve–sparing procedures with nerve-sacrificing procedures
(eg, radical neck dissection) using a battery of physical therapy measurements.
They found that nerve–sparing procedures were associated with better
preservation of shoulder function. Sobol and Jensen1
found that patients undergoing SND demonstrated functional capacity and perception
of shoulder pain 16 weeks following surgery that was superior to those undergoing
MND and radical neck dissection; however, there were limited long-term data
available in their study. Also, none of the aforementioned studies used a
validated QOL instrument. Recently, Terrell et al16
reported findings from the University of Michigan Head and Neck QOL (UMHNQOL),
an instrument that specifically assessed shoulder pain as a single item within
the context of a general head and neck QOL instrument. They reported that
patients undergoing nerve-sparing level V neck dissections experienced more
shoulder or neck pain than patients in whom level V was undissected. Compared
with the UMHNQOL, the NDII assesses shoulder-related QOL in a more comprehensive
and detailed manner. It is a multi-item, validated instrument developed to
evaluate a wide range of components of shoulder-related QOL after neck dissection.
An analysis of single items in the NDII showed significant QOL differences
in pain scores between patients undergoing SND and those undergoing MRND.
Additionally, the NDII demonstrated that there were also significant QOL differences
by neck dissection type in the areas of lifting light objects and leisure
and recreation pursuits.
Radiation treatment was a significant variable that was a predictor
for unfavorable shoulder-related QOL in our study. Schuller et al6 sought to evaluate the impact of surgery and radiation
on shoulder function. The study found that the patients who received radiation
in addition to surgery more frequently reported an increased reliance on others.
Although an excellent study with important findings, a validated QOL instrument
needed to be used to evaluate this patient population. Our study confirmed
the results of the study by Schuller and colleagues with a validated questionnaire
(NDII) and demonstrated that the use of radiation in patients undergoing neck
dissections is an independent, negative prognosticator of shoulder function.
Weight was not only important to the model, it was also significant
as an independent variable. We postulated that weight was a surrogate for
overall patient physical well-being and nutritional status and therefore had
a positive correlation with health-related QOL for shoulder function. It seems
intuitive that more robust patients would have better recuperative and compensatory
powers for maintenance of shoulder function and, thus, have less QOL-related
impairment.
Age was an important contributor in our regression model for shoulder-related
QOL following neck dissection, even after controlling for the other clinical-demographic
factors. The older the patient, the less impact there was in QOL. It was our
supposition that older patients might not perceive substantial functional
deficits as having proportionally as great an impact on QOL, perhaps due to
lower demands on shoulder function or lower expectations of their physical
capacity related to their shoulder function compared with younger patients.
It was our goal to develop and validate a QOL instrument to assess shoulder
function and to systematically determine which treatment, clinical, and demographic
factors best predict long-term shoulder QOL impairment following neck dissection.
Thus, we developed a validated QOL instrument, the NDII. Age, weight, radiation
treatment, and neck dissection type were the variables that most affected
QOL. Higher-risk patients (eg, younger, less robust patients who receive radiation
treatment and MRND) might benefit from early, more aggressive rehabilitative
intervention.
AUTHOR INFORMATION
Accepted for publication August 6, 2001.
Corresponding author and reprints: Douglas B. Chepeha, MD, MSPH,
Department of Otolaryngology–Head and Neck Surgery, 1500 E Medical Center
Dr, Taubman Center 1904, University of Michigan, Ann Arbor, MI 48109 (e-mail: dchepeha{at}umich.edu).
From the Department of Otolaryngology–Head and Neck Surgery,
University of Michigan, Ann Arbor (Drs Taylor, Teknos, Bradford, Sharma, Terrell,
Hogikyan, Wolf, and D. B. Chepeha); and the Department of Physical Therapy,
Glen Sather Sports Medicine Clinic, University of Alberta, Edmonton (Ms J.
C. Chepeha).
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