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Practical Information
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Instrument Name:
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Skindex-29
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Instrument Description:
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The Skindex-29 measures the effects of skin disease on patients’ quality of life. The Skindex-29 is comprised of the 10-item Emotions, 7-item Symptoms, and 12-item Functioning subscales.
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Price:
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Free (in public domain)
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Administration Time:
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5 minutes (Ref: 1)
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Publication Year:
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1997
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Item Readability:
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Flesch-Kincaid reading level of 4.7; items are written in simplistic language and most have 10 or fewer words.
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Scale Format:
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30 questions; answer choices are Never, Rarely, Sometimes, Often, All the Time
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Administration Technique:
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Self-administered by patient
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Scoring and Interpretation:
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Ordinal choices range from "Never=0" to "All the time=4"; values are summed. Higher scores indicate skin condition impacts more on quality of life (Ref: 1)
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Forms:
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The Skindex-29 is 30 items and requires 5 minutes to complete; the original Skindex, which contains 61 items, requires 15 minutes to complete and was found to be less responsive to change (Ref: 1); a Skindex-16 also exists.
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Research Contacts
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Instrument Developers:
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Mary-Margaret Chren, MD; Rebecca J. Lasek, PhD; Susan A. Flocke, PhD; Stephen J. Zyzanski, PhD
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Instrument Development Location:
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Department of Dermatology and the UCSF-Mt. Zion Center on Aging, University of California, San Francisco, San Francisco VAMC 111-G, 4150 Clement St., San Francisco, CA 94121
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Instrument Developer Email:
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mmchren@itsa.ucsf.edu
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Instrument Developer Website:
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No information found.
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Annotated Bibliography
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1. Chren MM, Lasek RJ, Flocke SA, Zyzanski SJ. Improved discriminative and evaluative capability of a refined version of Skindex, a quality-of-life instrument for patients with skin diseases. Arch Dermatol 1997 Nov;133(11):1433-40. [PMID 9371029]
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Purpose: The authors refined the original 61-item Skindex to a 30-item measure because it was observed that the original took too long for routine clinic administrations, patients may not have been able to discriminate questions well, and some scales were less responsive to change. |
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Sample: 692 patients returned completed measures for this study. Patients from private dermatology offices in Cleveland, OH and the general dermatology clinic at the Cleveland VA Medical Center. |
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Methods: Items from the original Skindex were analyzed for inconsistent responses and whether they contributed sufficiently to the overall reliability and validity of the scales. Factor analysis was performed and new items were added. The refined measure was administered once and readministered to the same sample by mail for reproducibility. The instrument was psychometrically analyzed. |
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Implications: This version of the Skindex was found to be responsive to clinical change and was quicker to complete. Correlations with dermatologists’ diagnoses was significant but modest for severity of skin disease. |
2. Chren MM, Lasek RJ, Quinn LM, Mostow EN, Zyzanski SJ. Skindex, a quality-of-life measure for patients with skin disease: reliability, validity, and responsiveness. J Invest Dermatol. 1996 Nov;107(5):707-13. [PMID: 8875954]
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Purpose: The authors’ aim was to develop and test an instrument to measure the quality of life of people who have skin diseases. |
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Sample: 201 patients (out of 266 approached) were randomly selected from private dermatology offices and from the general dermatology clinic at the Cleveland VA Medical Center. 60% were female and the mean age was 51±17 years; 91% were white; 20% were veterans. 67 of 100 patients randomly selected from the primary sample for responsiveness testing returned their responses. |
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Methods: The Skindex was administered along with sociodemographic and clinical questions. The dermatologist was asked to rate the severity of each patient’s condition. Data were analyzed and psychometric calculations were performed. |
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Implications: The Skindex was found to be a reliable and clinically responsive measure for assessing quality of life in patients with skin diseases. |
3. Abeni D, Picardi A, Pasquini P, Melchi CF, Chren MM. Further evidence of the validity and reliability of the Skindex-29: an Italian study on 2,242 dermatological outpatients. Dermatology. 2002;204(1):43-9. [PMID: 11834849]
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Purpose: The authors aimed to deliver additional reliability and validity data in support of the Skindex-29 using an Italian language version of the measure. |
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Sample: 2,242 Italians completed the instrument (4,268 distributed, 3,125 returned, and 267 returned blank.) The sample was drawn from outpatient clinics at a large dermatological hospital in Rome, Italy. All patients were 18 or older. |
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Methods: The instrument was administered along with the reliable and valid Italian version of the General Health Questionnaire (GHQ-12), a 12-item measure used to detect psychological distress and non-psychotic psychiatric disorders. |
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Implications: The instrument was found to support previous studies as being reliable, valid and consistent in its factor structure. |
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Factors and Norms
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Factor Analysis Work:
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There are three factors used in this version: emotions, symptoms, and functioning. The original version had eight, which after item analysis, the authors found that some of the original factors were redundant. Five new items were added and some items were rephrased to better address the new constructs. Exploratory factor analysis using oblique rotation revealed that these factors accounted for 97% of the common variance of the correlation matrix. Before revision, these three factors accounted for 89% of the common variance of the correlation matrix. (Ref: 1) Factor analysis of the larger Italian sample also revealed three factors, accounting for 49.3% of the total variance (the percentage of common variance was not given).
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Normative Information Availability:
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No information found.
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Reliability Evidence
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Test-retest:
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The instrument was assessed for reproducibility on a sample of 105 from the original group 72 hours after the first administration. The authors reported Pearson’s correlation coefficients for the three factors: Emotions (0.88), Symptoms (0.91) and Functioning (0.92.) (Ref: 1) In a sub-sample of 112 for the Italian version, within a 1-week period, the intraclass correlation coefficients were: 0.83 for Emotions, 0.89 for Symptoms and 0.89 for Functioning. (Ref: 3)
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Inter-rater:
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The Skindex-29 was developed as a self-report instrument. The reliability of rater-completed instruments has not been assessed.
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Internal Consistency:
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The authors reported the following Cronbach alpha values for each factor: Emotions (0.94), Symptoms (0.87) and Functioning (0.96.) (Ref: 1) In a sample of 2242, the Italian version of the Skindex-29 demonstrated Cronbach alpha values of 0.87 for the Emotions factor, 0.86 for Symptoms factor and 0.90 for the Functioning factor. (Ref: 3)
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Alternate Forms:
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No information found.
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Validity Evidence
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Construct/ Convergent/ Discriminant:
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The authors who administered the Italian version reported that mean scores of patients with inflammatory skin diseases were significantly higher (p<0.001) than those with isolated skin diseases. Convergent validity evidence was gathered using data from 2186 patients who completed the Skindex-29 and the General Health Questionnaire (GHQ-12). Pearson’s correlations for Skindex-29 Symptom scores and GHQ-12 social dysfunction and general dysphoria scales were 0.26 and 0.22. Correlations between GHQ-12 social dysfunction and Skindex-29 functioning and emotions were 0.39 and 0.33. Correlations between GHQ-12 dysphoria and Skindex-29 functioning and emotions were 0.45 and 0.47. Correlations with physician judgments regarding severity of skin disease did not exceed 0.31 (Symptoms), 0.30 (Emotions) and 0.31 (Functioning.) (Ref: 3)
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Criterion-related/ Concurrent/ Predictive:
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No information found.
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Content:
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One researcher evaluated content validity by examining patients’ responses to an open-ended question. The answers were categorized, rank ordered by frequency, and compared with the items of the instrument. Results indicated that the items on the Skindex assessed the issues that patients noted in their responses to the open-ended question. (Ref: 1)
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Responsiveness Evidence:
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The authors reported scale scores for people who took the Skindex-29 at Time 1 and Time 2, three months later, and grouped by patient status (worse, unchanged, better) and within each construct (symptoms, emotions, functioning.) Differences with the worse or better groups exhibited scores that were statistically different (p<0.01 or p<0.001) in the expected direction. The unchanged group did not exhibit statistically different scores from Time 1 and Time 2 (Ref: 1)
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Scale Application in VA Populations:
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Yes. The measure was administered to patients in a dermatology clinic at a VA hospital. (Ref: 1)
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Scale Application in non-VA Populations:
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Yes. The measure was administered to patients in private practice dermatology offices. (Ref: 1) Also was administered to 2242 Italians (Italian version). (Ref: 3)
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Comments
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Overall, the Skindex-29 appears quite useful as a research measure. The Skindex-29 is easy to administer, and appears to have good psychometric qualities, including acceptable internal consistency and stability, as well as a consistent factor structure and demonstrated ability to detect change in condition and to discriminate among patients within broadly differing levels of severity in their skin conditions. The validity evidence could be stronger, as indicated by the authors, who recommend that future studies gather evidence of the convergent and discriminant validity of the Skindex. In addition, the correlations between physicians’ ratings and the Skindex-29 subscales were 0.31 and smaller. The low correlations were noted by the authors, who suggested that they might not indicate a problem with the Skindex-29, as they could be due to the poor validity of the physicians’ ratings. As yet, there has been no work on its reliability and utility as an instrument for tracking individual change (i.e., as a clinical measure). Furthermore, the Skindex-29 has been used in VA populations, but its properties have not been evaluated separately in veterans.
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Updates
No information found.
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