The norwegian version of the psoriasis disability index--a validation and reliability study

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.

Identification of psoriatic patients at risk of high quality of life impairment

Psoriasis is a systematic chronic disease with large influence on patients' quality of life (QoL). The aim of this study was to assess the QoL of patients with psoriasis using generic, dermatology-specific and psoriasis-specific instruments simultaneously, to investigate the relationships between dimensions or subscales of the questionnaires and to identify categories of patients at risk of a high QoL impairment. The study comprised 100 consecutive patients with psoriasis treated at the Department of Dermatology, Clinical Center "Zvezdara", Belgrade, from January to December 2011. Three QoL questionnaires were administered: the EuroQol-5D (EQ-5D), the Dermatological Life Quality Index (DLQI) and the Psoriasis Disability Index (PDI). The Psoriasis Area and Severity Index was used in evaluating disease severity. According to our results the QoL of psoriatic patients was impaired (the overall DLQI and PDI scores were 10.5 ± 7.2 and 13.4 ± 8.7, respectively, while EQ visual analog scale score was 48.8 ± 25.1). The most predictive factor of QoL impairment was disease severity, followed by sole and nail involvement. Psoriatic arthritis and bleeding were also associated with impaired QoL. Significant correlations between the instruments used in this study were in the expected directions. Mainly strong and moderate significant correlations ranging 0.26-0.84 were seen between DLQI and PDI instruments. A detailed approach to QoL assessment may give to the dermatologist useful information that could be of help in identifying patients belonging to categories at risk of high QoL impairment due to psoriasis, thus guiding them in clinical practice.

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.