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Scalpdex
A Quality-of-Life Instrument for Scalp Dermatitis
Suephy C. Chen, MD, MS;
Jensen Yeung, MD;
Mary-Margaret Chren, MD
Arch Dermatol. 2002;138:803-807.
ABSTRACT
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Objective To develop a scalp dermatitis–specific quality-of-life instrument.
Methods Based on the results of directed focus sessions with 8 patients with
scalp psoriasis or seborrheic dermatitis, we conceptualized 3 major constructs
that explain the way scalp dermatoses affect patient quality of life: symptoms,
functioning, and emotions. We constructed a 23-item instrument, Scalpdex,
and tested its reliability, responsiveness, and validity.
Results Fifty-two dermatology patients completed the study. We demonstrated
construct validity by confirming that the factors derived by principal axes
factor analyses with orthogonal rotation correlated to our hypothesized scales
(r = 0.76-0.84) and that differences in symptom,
functioning, and emotion scores differed among the varying levels of self-reported
scalp severity more than would be expected by chance (P<.05 by analysis of variance). The instrument demonstrated reliability
with internal consistency (Cronbach  , 0.62-0.80) and reproducibility
(intraclass correlation coefficient, 0.90-0.97). The quality-of-life scores
changed in the expected direction in our test for responsiveness (P .05, by paired t test for functioning
and emotion for those who improved). We ascertained the discriminant capability
of Scalpdex compared with a dermatological generic quality-of-life tool, Skindex,
by demonstrating superior responsiveness (P.005
by paired t test in functioning and emotion) and
improved overall sensitivity in individual items.
Conclusions Scalpdex is, to our knowledge, the first quality-of-life instrument
specifically for patients with scalp dermatitis that is reliable, valid, and
responsive. Clinicians can use the instrument to determine which aspect of
the disease most bothers the patient and to evaluate quality of life as one
variable of responsiveness to the therapeutic intervention.
INTRODUCTION
MANY PEOPLE experience the adverse effects of scalp dermatitis, from
its symptoms to its negative social profile.1-2
Scalp dermatitis is predominantly caused by 2 common inflammatory dermatoses:
psoriasis and seborrheic dermatitis. Psoriasis affects approximately 2% of
the general population, of which 50% to 90% have scalp involvement.3 Seborrheic dermatitis affects 1% to 3% of the general
population, and up to 95% of these patients have involvement of the scalp.2
Patients with scalp dermatitis routinely ask physicians for help, and
pharmaceutical companies constantly develop new products to control the disease.
An instrument that can measure and quantify scalp dermatitis–related
quality of life would be helpful for both physicians and pharmaceutical companies,
especially since studies have demonstrated that most physicians underestimate
the impact of disease on quality of life4 and
that objective clinical variables of skin disease are often poorly correlated
with impact on quality of life.5-6
There are several generic cutaneous quality-of-life instruments, but a scalp
dermatitis–specific survey does not exist. Although a generic instrument
is valuable to compare quality of life among different diseases, a disease-specific
instrument is more sensitive to quality-of-life issues relevant to the disease
in question. A disease-specific instrument may also be more sensitive to changes
over time.7
We developed a scalp dermatitis–specific instrument, Scalpdex,
based on constructs that patients specifically mentioned in directed focus
sessions and tested the measurement properties of the instrument in a sample
of patients with scalp dermatitis. We based the instrument on previous work
with Skindex,8 a measure of the effects of
skin diseases of all types on patient quality of life; the measurement properties
of Skindex have been studied extensively.8
We tested the scalp-specific instrument for validity, reliability, and responsiveness.
PATIENTS AND METHODS
All patients were recruited from the Stanford Dermatology Clinic. Consent
was obtained from all patients in accordance with the Administrative Panel
on Human Subjects in Nonmedical Research at Stanford University, Stanford,
Calif.
ITEM DEVELOPMENT
We conducted in-depth interviews with 4 patients with scalp psoriasis
and 4 patients with seborrheic dermatitis in which we asked open-ended questions
to elicit all the ways that their scalp condition affected their lives. We
interviewed patients to a point of saturation where no new information was
elicited. Based on all patient mentions and frequency, we conceptualized 3
major constructs that explain the way scalp dermatoses affect patient quality
of life: symptoms, functioning, and emotions. These are the same constructs
used in Skindex.8 We composed 14 scalp dermatitis–specific
items from the interview session information (Table 1). We also determined that 9 items from the 29-item version
of Skindex8 were important to comprehensively
assessing the constructs patients found relevant (Table 1). We called the 23-item survey "Scalpdex." For all items,
we used the same format as for the Skindex items but changed the wording "skin
condition" to "scalp condition." All items inquired about the past 4 weeks.
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Table 1. Scalpdex Items, in the Order Presented to Patients*
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SAMPLE POPULATION, MEASURES, AND DATA COLLECTION
A list of patients from the Stanford Dermatology Clinic with seborrheic
dermatitis or scalp psoriasis was obtained based on International
Classification of Diseases, Ninth Revision, codes. Patients were randomly
selected from the list. Interviewers administered the adapted Skindex-29,
the 14 scalp dermatitis–specific items, 5 global questions about their
general health and scalp condition, and 3 demographic questions to patients
by telephone. Patients answered all questions at baseline, 72 hours (allowable
range, 3-7 days), and 1 year. The demographic questions were omitted from
the latter 2 interviews.
SCORING
A patient's scale score was the average of his or her responses to items
in a given scale. For example, the scale score for emotion was the average
of all responses to the items in the emotion scale. Responses to item 18,
"caring for my scalp condition is inconvenient for me," were reverse scored.
The responses to the items were "never," "rarely," "sometimes," "often," and
"all the time." All reported scores were converted from the 1 to 5 scale to
a 0 to 100 scale.
PSYCHOMETRIC EVALUATION
We tested the instrument for reliability, responsiveness, and validity.
Reliability is the extent to which a measure yields the same results on independent
repeated trials under the same conditions, reflecting the degree to which
the instrument is free from random error. We evaluated reliability with internal
consistency via the Cronbach coefficient and with reproducibility
via the intraclass correlation coefficient. Responsiveness is the ability
to detect a change in the quality of life of the scalp condition. We tested
for responsiveness by applying the paired t test
to the baseline and 1-year answers for 3 groups: those reporting improvement,
no change, or worsening of their scalp condition.
Validity is evidence that the instrument is actually measuring what
it is supposed to measure.9 We confirmed validity
by examining face, content, construct, and discriminant validity. Face validity
refers to whether an instrument seems to be measuring what it is intended
to measure. Content validity is the completeness with which an instrument
covers the important areas of the domain that it is attempting to represent.
We ensured face and content validity of the instrument by interviewing patients
with scalp dermatitis in directed focus sessions.
Construct validity is the extent to which a particular instrument relates
to other measures in a manner that is consistent with theoretically derived
hypotheses concerning the constructs that are being measured. We tested construct
validity in 2 ways. We had hypothesized that the items would cluster into
3 factors that could be labeled as "symptoms," "functioning," and "emotions."
We tested this hypothesis by using principal axes factor analyses followed
by an orthogonal rotation. We retained only those factors with eigenvalues
greater than 2 and by application of the scree test.10
We identified the factor onto which items loaded by selecting the largest
coefficient of that item among all the retained factors. Each factor was labeled
by the predominant trait of the heavily loaded items. We compared the a priori
hypothesized scale assigned to each item to the factor onto which each item
loaded. We also compared the regression factor scores to the unweighted hypothesized
scale scores using Pearson correlation coefficients. We also tested construct
validity by comparing the scale scores with the self-reported severity of
the scalp condition using 1-way analysis of variance. We hypothesized that
the scale scores correlate with the severity of the scalp condition.
Discriminant validity is the extent to which one instrument measures
a certain health characteristic better than another instrument. Because Skindex
is a generic quality-of-life instrument, we hypothesized that it was not sensitive
enough to adequately measure quality-of-life issues specific to Scalpdex.
We tested for discriminant validity by comparing scores from Scalpdex to Skindex
in 2 ways. First, we examined the relative degree of responsiveness over time
by comparing the difference in responsiveness between baseline and 1 year.
Second, we qualitatively assessed the degree of sensitivity of the items to
scalp quality of life. After examination of the distribution of the answers
to a given item, we considered that item to be relatively insensitive to scalp
dermatitis quality of life if more than 50% of the patients chose a particular
answer.
ANALYSES
All statistical analyses were performed using a statistical software
program (SPSS 10.0 for Windows; SPSS Inc, Chicago, Ill). All data are give
as mean (SD).
RESULTS
DEMOGRAPHICS AND DISEASE CHARACTERISTICS
We contacted and invited 155 patients to participate in directed focus
sessions and instrument validation. Approximately 55% of the invited patients
declined to participate, most because their psoriasis or seborrheic dermatitis
did not involve the scalp (25%), they did not have psoriasis or seborrheic
dermatitis (15%), or they were not interested (15%). The remainder were not
available because the wrong telephone number was listed or they did not answer
our calls. Seventy patients agreed to participate in the study. One patient
dropped out at the 72-hour point, and 17 dropped out at the 1-year point.
The overall patient age was 47.6 (15.2) years; for patients with psoriasis,
the age was 47.2 (15.5) years, and for those with seborrheic dermatitis it
was 48.0 (15.1) years.
Of the 52 patients who completed the study, 25 had psoriasis (12 women
and 13 men) and 27 had seborrheic dermatitis (16 women and 11 men). Most of
the patients rated their scalp condition as being poor to fair (58% [n = 30])and
of more than 10 years' duration (65% [n = 34]).
ITEM ANALYSIS
Scalp-related quality of life was most affected by "my scalp itches,"
with a score of 56.1 (28.7). Quality of life was least affected by feeling
"humiliated," with a score of 12.3 (24.5). Mean scores for all items are listed
in Table 1.
Several items proved to be relatively insensitive, that is, more than
50% of the respondents answered "never" to these items, including "bothered
by questions" (59% [n = 31]), "affected color of clothes" (65% [n = 34]),
"bothered by cost" (58% [n = 30]), "daily life difficult" (68% [n = 35]),
"makes me feel different" (55% [n = 29]), "hard to go to the barber or hairdresser"
(58% [n = 30]), "depressed" (62% [n = 32]), "ashamed" (52% [n = 27]), and "humiliated"
(73% [n = 38]).
RELIABILITY
Each of the 3 scales demonstrated internal consistency reliability,
with Cronbach coefficients ranging from 0.62 to 0.80 (Table 2). Systematically deleting one item from the analysis did
not significantly increase the coefficients. Each of the 3 scales demonstrated
reproducibility, with intraclass correlation coefficients ranging from 0.90
to 0.97.
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Table 2. Psychometric Test Results*
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RESPONSIVENESS
Patients were divided into 3 categories (better, worse, or no change)
based on their responses to the question, "How has your scalp condition changed
since the first interview?" Eighteen patients reported improvement, 3 reported
worsening, and 31 reported no change. Using the scalp dermatitis–specific
scale scores (Table 1), we found
improvement in the quality-of-life scores of patients who reported improvement
in their dermatitis; the difference was statistically significant (P.005, using paired t test) for functioning
and emotion scores (Table 3).
We found no significant differences in the scores of those who reported no
change. We expected and found no significant difference in patients who reported
worsening of scores given that there were only 3 patients.
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Table 3. Responsiveness Scores
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CONSTRUCT VALIDITY
After factor analysis with orthogonal rotation, 3 factors were retained
according to the criteria outlined in the "Patients and Methods" section.
From the items that loaded most heavily on factor 1, the predominant trait
was emotions; on factor 2, functioning; and on factor 3, symptoms. The Pearson
correlation coefficient comparing the regression factor scores and the unweighted
hypothesized scale scores ranged from 0.76 to 0.84. The correlation between
the regression factor scores and the other 2 scales (eg, factor 1 with symptoms
or emotions) were much lower, in the range of 0.07 to 0.67 (Table 2).
We compared the scale scores (symptoms, functioning, and emotions) with
self-reported scalp condition severity. Severity levels were determined on
a 5-point scale: poor, fair, good, very good, and excellent. We found greater
differences in symptom, functioning, and emotion scores among the different
levels of scalp severity than would be expected by chance (P<.05, by analysis of variance). The pairwise multiple comparison
procedure revealed a significant difference in symptoms, emotions, and functioning
among a variety of severity ratings (Figure
1).
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Differences in self-rated severity of scalp dermatitis in terms of
symptoms, emotions, and functioning. The black boxes represent differences
in the categories that were significantly different (P<.05).
For instance, there was a significant difference in symptoms between patients
who rated their scalp condition as "poor" and those who rated it as "fair."
The white boxes represent no difference between the 2 categories, eg, in emotion
between those patients who rated their scalp condition as "fair" and those
who rated it as "good." P indicates poor; F, fair; G, good; VG, very good;
and E, excellent.
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DISCRIMINANT VALIDITY
We demonstrated the discriminant validity of Scalpdex. Scalpdex had
a higher degree of responsiveness over 1 year than did Skindex for emotions
and functioning (P.005 by paired t test). We neither expected nor found any difference in symptom responsiveness
since the items for symptoms are the same in the 2 instruments. We also ascertained
that Scalpdex was relatively more sensitive than Skindex during our item analysis.
In 9 Scalpdex items (39%) vs 17 Skindex items (59%), at least 50% of the patients
answered "never." Note that 3 of the items are used in both Scalpdex and Skindex.
COMMENT
This study presents, to our knowledge, the first quality-of-life instrument
specifically for patients with scalp dermatitis. We demonstrated the reliability,
responsiveness, and validity of the instrument. We demonstrated reliability
with high internal consistency reliability, as shown by substantial and robust
Cronbach coefficients for all 3 scales, and reproducibility, as shown
by the high intraclass correlation coefficients. We ascertained responsiveness
by demonstrating that the scores improved in patients who reported improvement
in their scalp condition and that the scores did not change in patients who
reported no change. The 3 patients who reported worsening did not provide
enough data for analysis.
An instrument may be reliable and responsive, but not valid. We ensured
face and content validity by deriving the items from directed focus sessions
with patients with either scalp psoriasis or seborrheic dermatitis. We confirmed
construct validity by finding that the scale scores correlated with self-reported
scalp condition severity. We also hypothesized that 3 constructs (symptoms,
emotions, and functioning) were being measured by the questionnaire, and we
confirmed the hypothesis with factor analysis of the data. We demonstrated
discriminant validity by ascertaining that that Scalpdex detected responsiveness
over time better than did Skindex. We also qualitatively demonstrated that
Scalpdex was more sensitive to quality-of-life issues than was Skindex.
Scalpdex can be used to aid physicians in their care of patients with
scalp psoriasis or seborrheic dermatitis. Although physicians are trained
to evaluate severity using clinical variables, quality of life is also an
important outcome when devising a therapeutic regimen. We showed that Scalpdex
is more sensitive and more able to detect responsiveness to changes in quality
of life of scalp dermatitis than a generic, cutaneous quality-of-life measure.
The instrument is practical to use in the office setting. The 52-item combined
testing instrument took, on average, 13.5 minutes to complete; the 23-item
Scalpdex instrument should only take 5 to 10 minutes. Further work can be
done with the instrument in terms of shortening it. We found that 9 of the
items are relatively insensitive to quality-of-life issues; these items may
be eliminated, and the resulting 14 items may be tested for validity and responsiveness.
However, we believe that a 5- to 10-minute instrument is manageable for patients
and clinicians.
Clinicians can use the instrument to help their patients in 3 ways.
First, the profile of the instrument can be analyzed to determine which aspect
of the disease most bothers the patient, for example, 2 patients may have
identical clinical presentations but one may be bothered by symptoms and the
other primarily by the appearance. Second, clinicians can evaluate changes
in quality of life as one variable of responsiveness to the therapeutic intervention.
Last, clinicians can use the impact on quality-of-life data to petition managed
care organizations and insurance companies in the event that they deny coverage
for therapies, citing the disease as a cosmetic issue.
AUTHOR INFORMATION
Accepted for publication January 21, 2002.
This study was supported by a Dermatology Foundation Clinical Career
Development Award sponsored by Galderma Laboratories Inc, Fort Worth, Tex
(Dr Chen); a Network 7 VISN Veterans Association Career Development Award
(Dr Chen); Mentored Patient Oriented Career Development Award K23AR02185-01A1
(Dr Chen), an Emory Skin Disease Research Center Project and Feasibility grant
2P30 AR 42687-07 (Dr Chen), and Career Mentored Scientist Award K08AR01962
(Dr Chren) from the National Institute on Arthritis and Musculoskeletal and
Skin Disease, National Institutes of Health, Bethesda, Md; and an unrestricted
educational grant from Connectics Inc, Palo Alto, Calif (Dr Chen).
We thank Lesley Woods, MA, from the Emory Center for Outcomes Research
for her editorial assistance.
A cooperative effort of the Clinical Epidemiology Unit of the Istituto
Dermopatico dell'Immacolata–Istituto di Ricovero e Cura a Carattere
Scientifico (IDI-IRCCS) and the Archives of Dermatology
Corresponding author and reprints: Suephy C. Chen, MD, MS, Department
of Dermatology and Emory Center for Outcomes Research, 1639 Pierce Dr, 5001
Woodruff Memorial Building, Atlanta, GA 30033 (e-mail: suephy{at}alum.mit.edu).
From the Department of Dermatology and Emory Center for Outcomes Research,
Emory University School of Medicine, and Departments of Health Services Research
and Development Medicine and Division of Dermatology, Atlanta Veterans Administration
Medical Center, Atlanta, Ga (Dr Chen); McMaster University, Hamilton, Ontario
(Dr Yeung); the Departments of Dermatology and Medicine, University of California
at San Francisco (Dr Chren); and the Dermatology Service, San Francisco Veterans
Affairs Medical Center (Dr Chren).
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Section Editors:
Damiano Abeni, MD, MPH, Rosamaria
Corona, DSc, MD, Paolo Pasquini, MD, MPH, Istituto Dermopatico dell'Immacolata,
Rome, Italy
Michael E. Bigby, MD, Beth Israel
Deaconess Medical Center, Harvard Medical School, Boston, Mass
Moyses Szklo, MD, MPH, DrPH, The Johns Hopkins University,
Baltimore, Md
Hywel Williams, MD, Queens Medical
Centre, Nottingham, England
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