The Psychometric Properties of the Psoriasis Disability Index in United States Patients

Patient-Reported Outcome Measures for Health-Related Quality of Life in Patients With Psoriasis: A Systematic Review

Importance

Multiple patient-reported outcome measures (PROMs) for health-related quality of life (HRQL) exist for patients with psoriasis. Evidence for the content validity and other measurement properties of these PROMs is critical to determine which HRQL PROMs could be recommended for use.

Objective

To systematically review the validity of HRQL-focused PROMs used in patients with psoriasis.

Evidence Review

Using PubMed and Embase, full-text articles published in English or Spanish on development or validation studies for psoriasis-specific, dermatology-specific, or generic HRQL PROMs were included. Development studies included original development studies, even if not studied in psoriasis patients per Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) recommendations. If a study included multiple diagnoses, more than 50% of patients had to have psoriasis or psoriasis-specific subgroup analyses available. Data extraction and analysis followed the COSMIN guidelines. Two independent reviewers extracted and analyzed the data, including PROM characteristics, quality of measurement properties (structural validity, internal consistency, cross-cultural validity, reliability, measurement error, criterion validity, construct validity, and responsiveness), and level of evidence. PROMs were classified into 3 levels of recommendations: (1) PROM recommended for use; (2) PROM requires further validation; and (3) PROM not recommended for use.

Findings

Overall, 97 articles were identified for extraction. This included 19 psoriasis-specific, 8 skin-specific, and 6 generic PROMs. According to COSMIN standards, most measures identified received a B recommendation for use, indicating their potential but requiring further validation. Only the Rasch reduced version of the Impact of Psoriasis Questionnaire (IPSO-11 Rasch) received an A recommendation for use given that it had sufficient content validity, structural validity, and internal consistency.

Conclusions and Relevance

This study identified a significant lack of information concerning the quality of HRQL measures in psoriasis. This gap in knowledge can be attributed to the fact that traditional measures were developed using validation criteria that differ from the current standards in use. Consequently, additional validation studies in accordance with contemporary standards will be useful in aiding researchers and clinicians in determining the most suitable measure for assessing HRQL in patients with psoriasis.

Cross-cultural adaptation and validation of the Bangla version of the Psoriasis Disability Index

Background

The Psoriasis Disability Index (PDI) is used for the quality-of-life assessment of psoriasis patients. However, a locally adapted Bangla version of the PDI (B-PDI) instrument is currently lacking in Bangladesh. To translate the instrument, adapt, and validate it among psoriatic patients of the country was the objective of the study.

Methods

Translation, adaptation, and back-to-back translation to Bangla were made from the original English PDI. The final Bangla instrument was applied among 83 psoriasis patients twice at 10 days intervals. The psychometric property of the instrument was evaluated. Item-level content-validity index (CVI) was used to check the content validity of the instrument. Convergent validity was tested by comparing the B-PDI with the validated Bangla version of Short Form 36(SF-36) and the Psoriasis Area Disability Index (PASI) score. Necessary testing was used to assess internal consistency and test-retest reliability.

Result

The B-PDI was well-accepted by the patients. It showed good internal consistency (Cronbach's alpha = 0.76) and very high test-retest reliability (Pearson r = 0.92, p < 0.001). The scale demonstrated excellent content validity (Content Valid Index [CVI] = 1). The instrument had satisfactory convergent validity with four components of SF-36. Pearson correlation coefficient for physical, emotional, social, and pain domains of SF-36 was 0.663, 0.644, 0.808, and 0.862, respectively, and for PASI score was 0.812. Factor exploration using Principal Component Analysis revealed four factors reflecting working disabilities, social, and hygienic disabilities, lifestyle difficulties, and leisure-associated disabilities.

Conclusion

This study supports the reliability and validity of the B-PDI instrument for measuring health-related quality-of-life for Bangla-speaking psoriasis patients.

Influence of psoriasis lesions' location and severity on psychosocial disability and psychopathology. Observational study and psychometric validation of the SAPASI Portuguese version

OBJECTIVES

The psychosocial impact of psoriasis is well documented. However, the contributing role of clinical disease characteristics is not satisfactorily explored. This study aimed to validate the Self-administered Psoriasis Area and Severity Index (SAPASI) to a Portuguese population (SAPASI-PT) and to perform its cross-validation, assessing how the results will generalize to an independent data set, with the Psoriasis Area and Severity Index (PASI), in order to assess the influence of psoriasis' severity on psychosocial disability and psychopathology.

METHODS

A cross-sectional study with 228 patients with psoriasis was carried out. Data was collected through a sociodemographic and clinical questionnaire, SAPASI-PT, the Psoriasis Disability Index (PDI) and the Brief Symptoms Inventory (BSI). The cultural and linguistic adaptation of SAPASI to a Portuguese version and the cross validation with PASI was carried out. Multiple associations between psychosocial disability, psychopathology and severity, discomfort and location of lesions were investigated through logistic regression models.

RESULTS

A good adjustment model for SAPASI-PT is found. Also, associations between psychosocial disability, psychopathology and the psoriasis severity and discomfort are found. The existence of lesions is positively associated with the severity of the disease. Patients with lesions in hands or genitals are those reporting a greater discomfort. The presence of lesions in hands is positively associated with PDI, i.e., with leisure and with treatment, marginally. Additionally, patients scoring higher in the personal dimension are found to have a significantly greater percentage of lesions in the genitals.

CONCLUSIONS

The psoriasis severity and location of lesions are important determinants of patients´ quality of life. Lesions on face, hands and genitals are associated with a higher impact on psychosocial wellbeing of patients. Psychological counselling should be considered within psoriasis treatment context in patients with the described disease manifestations.

Validation of psoriasis disability index (PDI) questionnaire Sinhala version

INTRODUCTION/OBJECTIVES

Psoriasis is a chronic inflammatory dermatosis with significant physical and psychological impact leading to negative influence on the quality of life among patients with psoriasis. Other than the disease characteristics many external factors could operate in South Asian context. Lack of a reliable disease-specific instrument prevents objective estimation and monitoring of disability in patients with psoriasis and hence we aim to validate assess the psychometric properties of the Sinhala version of PDI.

METHODS

A cross-sectional study conducted at dermatology clinic at a tertiary care National Hospital in Sri Lanka. Patients with psoriasis and on therapy at least 4 weeks prior to enrollment, aged more than 18 years, were included while those with already diagnosed psoriatic arthritis and/or nail psoriasis alone without any skin involvement and generalized pustular psoriasis de novo were excluded. All patients were examined by dermatologist to obtain disease characteristics. The reliability was assessed by internal consistency using Cronbach's α and item-total correlation. Convergent validity was measured with the known groups.

RESULTS

Of 199 patients studied, the PDI Sinhala version showed Cronbach's α of 0.86 (all 15 items) and ranged from 0.57 to 0.77 for subscales. PDI score and Dermatology Life Quality Index (DLQI) showed good correlation of coefficient 0.76 (p < 0.01). Positive associations were noted with extent and severity of psoriasis when using sample medians (p < 0.05). The dimensionality of the PDI was determined using exploratory factor analysis and four factors were structured.

CONCLUSION

The PDI Sinhala version is proved to be valid and reliable tool to assess the burden of psoriasis among Sinhala conversant patients in Sri Lanka.

Evaluation of the correlation between scales determining disease severity in patients with moderate-severe chronic plaque-type psoriasis

BACKGROUND

Psoriasis is a chronic erythematous-squamous disease. The results of studies related with the correlation between methods used in determining disease severity are contradictory.

AIMS

The aim of this cross-sectional study is to evaluate the correlation between Psoriasis Area and Severity Index (PASI) and body surface area (BSA) involvement which are used to determine psoriasis severity and which are evaluated by the physician and Dermatology Life Quality Index (DLQI) and Psoriasis Disability Index (PDI) which are evaluated by the patients.

METHODS

Demographic data, PASI, BSA, DLQI, and PDI values of the patients were recorded. The correlation between the scales was evaluated.

RESULTS

51 patients, 11 female (21.6%) and 40 male (78.4%), were included in the study. Average age was found as 44.76 ± 11.14, while average disease duration was found as 20.74 ± 7.94. Average PASI, BSA, DLQI and PDI values were found as 17.27 ± 7.49, 33.90 ± 13.87, 15.09 ± 7.48, 23.58 ± 10.20, respectively. In the evaluation of the correlation between the scales, while PASI was found to be correlated with BSA involvement (r = 0.780 P = .000), DLQI and PDI were not found to be correlated. On the other hand, correlation was also found between DLQI and PDI (r = 0.641 P = .000).

CONCLUSION

There is no correlation between physical assessment methods (PASI, BSA) and quality of life scales (DLQI, PDI).

Patient-reported outcomes assessment tools for use in psoriasis in Spain: A systematic review

OBJECTIVES

To review the literature on validated tools for measuring patient-reported outcomes (PROs) in psoriasis in Spain. To evaluate the psychometric properties of the tools and describe the results of their practical application.

MATERIAL AND METHODS

Systematic review of studies validating or using instruments for assessing PROs in Spanish patients with psoriasis. Literature searches were performed in international (PubMed/Medline) and Spanish (Medes, Ibecs) databases. We also searched databases of instruments for measuring PROs (BiblioPRO, PROQOLID). The review included studies published in English or Spanish up to January 9, 2017. We also checked the reference lists of the key publications identified. The quality of the questionnaires was evaluated based on their psychometric properties (construct, transcultural adaptation, reliability, validity, feasibility, and sensitivity to change).

RESULTS

Eighteen publications were included. Six articles described the validation of Spanish versions of 5 PROs tools: 4 health-related quality of life (HRQoL) questionnaires specific to psoriasis and dermatologic diseases and 1 questionnaire specific to satisfaction with treatment. Our assessment of the HRQoL tools' psychometric properties showed that the PSO-LIFE questionnaire received the highest scores, although specific properties varied from instrument to instrument. The 12 remaining articles were observational studies that used the validated instruments. In use, these tools detected the high impact of psoriasis on HRQoL, especially in young female patients with severe disease.

CONCLUSIONS

We identified 5 specific instruments validated in Spain for scoring PROs in patients with psoriasis. The tools' psychometric properties vary, and it is essential to understand their strengths and weaknesses when selecting the right one for each situation. In use, these questionnaires are able to detect the high impact of psoriasis on patients' HRQoL. PROs provide useful information to complement routine clinical findings in psoriasis and may contribute to improving disease management.

Rasch analysis holds no brief for the use of the Dermatology Life Quality Index (DLQI) in Chinese neurodermatitis patients

BACKGROUND

The Dermatology Life Quality Index (DLQI) is the most widely used measure of health-related quality of life (HRQoL) associated with skin disease. Recently, the psychometric properties of the DLQI have caused some controversy because the instrument appears not to meet the requirements of modern test theory. The purpose of this study was to assess whether these psychometric issues also occur in Chinese patients with neurodermatitis.

METHODS

One hundred fifty consecutive outpatients (83 males and 67 females) seeking treatment for neurodermatitis were assessed for eligibility for this prospective study between July 1, 2011 and September 30, 2011. The DLQI and a demographic questionnaire were completed. One female participant who incompletely answered the DLQI was excluded. Data were analyzed using the Rasch model in order to obtain meaningful scores for the DLQI. Scale assessment included analysis of rating scale function, item fit to the Rasch model, aspects of person-response validity, unidimensionality, person-separation reliability, and differential item function.

RESULTS

The rating scale advanced monotonically for all items in the DLQI, but item 9 did not demonstrate acceptable goodness-of-fit (Infit MnSq values >1.3) to the Rasch model. The 10 items of the DLQI met the criteria for person-separation reliability (PSI = 2.38) and the first latent dimension (general QoL) accounted for 50.8 % of the variance; but the variance explained by the second dimension (7.1 %) exceeded the criterion of 5 %. There were also limitations related to person-response validity, because ≥ 5 % (18.1 %) of cases demonstrated unacceptable fit. There was no uniform differential item functioning.

CONCLUSIONS

For neurodermatitis patients, the DLQI seems to have poor fit to the Rasch model; therefore, we recommend against using this instrument with neurodermatitis patients.

Patient-reported outcome measures in psoriasis: the good, the bad and the missing!

As a long-term condition, psoriasis demands significant personal and professional input for optimal self-management. Low levels of well-being and high levels of psychological distress in patients with psoriasis are associated with reduced resources for self-care. Patient-reported outcome (PRO) measures can be used to assess physical, social and psychological functioning in order to guide treatment. In this article, we systematically reviewed the development and validation of existing PRO measures. PubMed (Medline), PsycINFO and CINAHL were searched systematically using predefined search terms. The search was limited to articles in the English language relating to human subjects. Articles were selected for full review through explicit inclusion/exclusion criteria. PRO measures were critically reviewed in accordance with the published guidelines and theory on the development and validation of PROs. The search identified 967 abstracts; 71 of these articles met the criteria for full review. In these 71 articles, 45 PRO measures were found: 16 were specific to psoriasis, 21 assessed other dermatological conditions and eight were developed for generic nondermatological health conditions. The review revealed several limitations of the existing measures, including: (i) a composite structure assessing multiple, poorly-defined concepts; (ii) a lack of evidence for face and content validity; (iii) a failure to include both patient and clinician perspectives and requirements and (iv) a lack of evidence regarding the feasibility and acceptability for patients and physicians. No single PRO measure with adequate evidence of validity, reliability and sensitivity to change captures patient well-being in psoriasis. A valid, sensitive, specific and acceptable PRO that assesses the full impact of psoriasis on well-being is needed for the comprehensive clinical management of psoriasis.

The development and validation of a disease-specific quality of life measure in hyperhidrosis: the Hyperhidrosis Quality of Life Index (HidroQOL©)

Purpose

To develop and validate a new disease-specific quality of life measure in hyperhidrosis for use in both routine clinical practice and clinical research.

Methods

Interviews and focus group discussions with hyperhidrosis patients, reported elsewhere, provided the content for the measure validated in this study (n = 71). A panel of dermatologists (n = 5) and patients (n = 7) carried out content validation. Further, item reduction and the initial construct validation were carried out in a cross-sectional study (n = 595), using the unidimensional Rasch analysis and exploratory factor analysis. Subsequently, the construct validity, reliability and responsiveness of the revised measure were assessed in a longitudinal study (n = 260). Data collection for the item reduction and the final validation phases was entirely carried out online.

Results

The expert panels judged the HidroQoL as content valid. Rasch analysis supported the revision of response options from five to three. Following removal of misfitting items, a set of 15 items showed optimal fit to the model (chi-squared statistic = 159.64, p = 0.07). Three additional items were retained on consideration of their importance to patients, resulting in an 18-item instrument. The items were grouped into two subscales, daily life activities and psychosocial life domains, based on results of the factor analysis. In subsequent construct validation, the HidroQoL correlated with the DLQI (r_s = 0.6, p < 0.01). Reliability was high (internal consistency, Cronbach’s alpha: overall scale = 0.9; test–retest reliability, Intra-class correlation = 0.9). The HidroQoL scores were sensitive to change in patients’ disease severity (score change from baseline to follow-up after 15–35 days, Cohen’s ES = 0.47).

Conclusion

This study has provided the initial evidence supporting measurement properties and the use of the HidroQoL instrument in both routine clinical practice and in research, for assessing quality of life impacts in hyperhidrosis.

Electronic supplementary material

The online version of this article (doi:10.1007/s11136-014-0825-2) contains supplementary material, which is available to authorized users.

Limited evidence of the effects of patient education and self-management interventions in psoriasis patients: a systematic review

OBJECTIVE

To describe the contents of educational and self-management programmes for patients with psoriasis, and to evaluate their effects.

METHODS

A systematic review of randomized controlled trials (RCTs), quasi-randomized trials and controlled clinical trials identified by a systematic literature search. Risk of bias was assessed by two independent reviewers and interventional effects were summarized descriptively and by meta-analysis.

RESULTS

Nine studies were included, which ranged from single brief interventions to long complex multidisciplinary programmes. Four RCTs with adequate sequence allocation were included to analyze interventional effects. One RCT compared two different educational programmes and found no differences between groups. The results of three trials that focused on combinations of education and self-management were heterogeneous. One RCT based on a 12-week comprehensive programme reported statistically significant effects (p<0.05) on disease severity and health-related quality of life. Two RCTs with less comprehensive programmes reported no effects on HRQoL.

CONCLUSION

This review showed that little evidence is available to support the effects of educational and self-management interventions in patients with psoriasis that are studied in RCTs. There is a significant lack of focused self-management and, compared with other chronic conditions, there appear to be few effective disease-specific tailored educational programmes for psoriasis.

Comparison of Skindex-29, Dermatology Life Quality Index, Psoriasis Disability Index and Medical Outcome Study Short Form 36 in patients with mild to severe psoriasis

BACKGROUND

Severity assessment of patients with psoriasis is a critical issue. Classical clinical assessment has recently been combined with quality of life (QoL) scores, but several instruments are used. Moreover, studies have focused on patients with moderate to severe psoriasis.

OBJECTIVES

To compare the characteristics of QoL instruments in patients with the full range of psoriasis severity attending dermatology clinics.

METHODS

Observational, prospective, multicentre study. Patients completed Skindex-29 (anchor) and a second instrument randomly selected from Dermatology Life Quality Index (DLQI), Psoriasis Disability Index (PDI) and Medical Outcome Study Short Form 36 (SF-36).

RESULTS

  Demographic data, Psoriasis Area and Severity Index and affected body surface area were not different between the three groups. Skindex-29 showed a weak but significant correlation with clinical severity; only PDI showed similar correlation. PDI, DLQI and SF-36 showed a substantial floor effect in patients with mild to severe psoriasis. Skindex-29 showed strong correlations with the other three QoL instruments. SF-36 was more sensitive than the other instruments in detecting worse QoL in male patients.

CONCLUSIONS

  Skindex-29 has better sensitivity to clinical severity with minimal floor effect, and covers the main domains explored by the other three QoL instruments in patients with mild to severe psoriasis.

Reliability and validity of the Chinese version of the Psoriasis Disability Index (PDI) in Chinese patients with psoriasis

Background

The Psoriasis Disability Index (PDI) is a widely used instrument to measure the impact of psoriasis on patients. There has not been psychometric evaluation of the Chinese version of PDI. The aim of this study was to evaluate its reliability and validity among Chinese patients with psoriasis.

Methods

A multi-center, cross-sectional study was conducted at 9 hospitals including patients aged 18 years and over. Reliability was determined by internal consistency using Cronbach’s alpha. Validity was assessed through convergent validity and known groups validity. Dimensionality of the PDI was examined by exploratory factor analysis in working patients and nonworking patients respectively.

Results

In all, 831 patients were studied. Internal consistency of the PDI was satisfactory. Cronbach’s alpha coefficient was 0.91 for the total score and over 0.70 for each subscale of the PDI. Evidence of convergent validity of the PDI was proved by excellent and moderate to good correlations with the Dermatology Life Quality Index (DLQI) and four subscales of the Short Form-36 (SF-36) (role-physical, bodily pain, social functioning, and role-emotional): r = 0.51-0.78. Known groups validity was confirmed that the PDI score discriminated well among patients with different severity of psoriasis. The dimensionality of the PDI was determined by the presence of two-factor structure for working patients and three-factor structure for nonworking patients which accounted for 57.3% and 62.3% of the variance respectively.

Conclusion

The Chinese version of the PDI is a reliable and valid instrument to assess the impact of psoriasis on patients’ lives and could be used in future quality of life assessment of Chinese patients with psoriasis.

Experience of effective treatment for patients with severe psoriasis

In this study was summarized the clinical monitoring of 6 patients with a vulgar severe psoriasis receiving a short course of Ustekinumab — antagonist of IL 12/23. Clinical monitoring demonstrated high efficiency of treatment with achievement of clinical remission and appreciable improvement in all patients; conservation of remission of psoriasis process till 6 months with regress of PASI more than 75 % from initial point in 5 from 6 patients; improvement of quality of life, absence of complications and adverse events during the treatment and the subsequent observation.

The reduced Impact of Psoriasis Questionnaire has good psychometric properties in Italian patients

BACKGROUND

A recent refinement study suggested that a Rasch reduced version of the Impact of Psoriasis Questionnaire (IPSO) of 11 items most adequately assessed the psychosocial impact of US psoriasis patients.

OBJECTIVE

To test whether the IPSO would also behave well in a different population that varies culturally, demographically, and in disease severity.

METHODS

The psychometric properties of the IPSO, using classical test and item response theory (Rasch analysis), were assessed in 805 Italian psoriasis patients.

RESULTS

Patients with more severe psoriasis reported significantly higher impact on their HRQOL (p < 0.001) and the IPSO correlated well with the Skindex-29 (r = 0.74) confirming its validity. The response distribution was adequate for all items, except item 9. The Cronbach's alphas were excellent and the high item-rest correlations confirmed its homogeneity. Principal component analysis demonstrated one dominant factor with an eigenvalue of 4.47 (items loading >0.40). Overall, the 11 IPSO items fitted the Rasch model (p = 0.07) and all items demonstrated a logical threshold order. Of the 11 items, 2 items showed significant individual misfit and only 1 item demonstrated significant differential item functioning for age but none for gender or global severity score.

CONCLUSION

The 11-item IPSO is a valuable psoriasis-specific HRQOL instrument in different populations.

Impacto de la psoriasis en la calidad de vida relacionada con la salud

BACKGROUND AND OBJECTIVE

Different studies have reported of physical, social and psychological disadvantages in patients with psoriasis. Nevertheless, its impact on the health-related quality of life is not clarified sufficiently. Our objective is to know the repercussion of the moderate-severe psoriasis on the health-related quality of life with the Psoriasis Disability Index (PDI).

PATIENTS AND METHOD

An observational, cross-sectional, international study developed in dermatology practices in Spain and Portugal. During a period of 9 months, 332 participating dermatologist included a minimum of 10 consecutive patients with moderate to severe psoriasis. The date report form includes information about the health-related quality of life (PDI), as well as objective variables of severity as body surface area and PASI (Psoriasis Area and Severity Index), pruritus, costs and willingness to pay.

RESULTS

A total of 3,320 patients were assessed. The majority of cases were males (57%) and the mean age at study inclusion time was 47 years. The mean value of the PDI was 8.93 (95% confidence interval, 7.83-9.21), which represents a percentage of global disability lower than 20%. The floor effect varies between 8.3% and 61.2%, and the ceiling effect varies between 0% and 3%. The correlations between the PDI and objective variables of severity (PASI and body surface area) were weak though statistically significant (p < 0.001) They all indicate that to higher severity of the psoriasis, upper negative impact in the health-related quality of life.

CONCLUSIONS

Psoriasis causes a negative impact in the health-related quality of life, though the magnitudes are weak and suggest some problems with the questionnaire. Possibly, the PDI reflects more the disability that the form in which the patients perceive and react to their state of health, and, several items seem to have a scanty applicability in the Spanish and Portuguese population. The PDI doesn't seem the appropriate instrument for this type of patients in our environment.

Refinement and reduction of the Impact of Psoriasis Questionnaire: classical test theory vs. Rasch analysis

BACKGROUND

Quality of life instruments are increasingly important in assessing disease severity. However, some of these measurements have been developed on a more or less ad hoc basis. Although not well standardized, psychometric analyses can be used to retest, refine and shorten existing quality of life instruments.

OBJECTIVES

To psychometrically test and refine the Impact of Psoriasis Questionnaire (IPSO) and to compare the results of two different statistical approaches.

PATIENTS AND METHODS

Among 792 psoriasis patients who were included in the PUVA Follow-up Study, we used classical test theory (CTT) and Rasch analysis to test and optimize the IPSO. Thereafter, two shortened versions of the IPSO derived from these models were compared.

RESULTS

CTT analyses of the original IPSO demonstrated suboptimal item performance for six of 16 items and inappropriate subscaling. In contrast to the original four subscales, factor analysis of the CTT version yielded three subscales (mental functioning, mental wellbeing and stigmatization). The Rasch approach, which included ordering of thresholds, differential item functioning and item fit, resulted in a unidimensional 11-item questionnaire. Although the two new versions of the IPSO shared only six items, both reflected the original IPSO well. However, several arguments such as lower correlation coefficients, higher Cronbach's alpha, ordered thresholds, unidimensionality and fewer differences among subgroups of patients suggested that the Rasch version of the IPSO may be the preferred instrument to use.

CONCLUSIONS

The IPSO can be improved and shortened and the Rasch-reduced version of this instrument is likely to assess the psychosocial impact of moderate to severe psoriasis on patients' lives best because it is a short, reliable and unidimensional measurement.

Testing and Reducing Skindex-29 Using Rasch Analysis: Skindex-17

The Skindex is a well-studied dermatology-specific health-related quality of life (HRQOL) instrument. The objective of this study was to test Skindex-29 using Rasch analysis and, if necessary, to refine it so that it would fit this item response theory based model. The Skindex-29 of 454 Italian dermatological patients was subjected to Rasch analysis to investigate threshold order, differential item functioning (DIF), and item and overall fit to the model. The Skindex-29 did not fit the Rasch model (P<0.001). The 5-point scoring system was re-grouped into three categories and demonstrated logical response order for all but one item. Rasch analyses of a combined emotion and social functioning subscale of Skindex-29 resulted in a 12-item psychosocial subscale. Five of seven items were retained in a symptoms subscale. Both subscales fitted the model (P=0.32 and 0.13, respectively) without significant individual item misfit or DIF (P>0.05). Classical psychometric properties such as response distribution, item-rest correlation, item complexity, and internal consistency of the two subscales of Skindex-17 were at least adequate. The Skindex-17 is a Rasch reduced version of Skindex-29, with two independent scores that can be used in the measurement of HRQOL in dermatological patients.