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Validation of psoriasis disability index (PDI) questionnaire Sinhala version

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Abstract

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

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Acknowledgements

The authors acknowledge of Dr. A Y Finlay for granting free license (License ID CUQoL1461) to use the PDI for validation of Sinhala version of Psoriasis Disability Index

Funding

The authors did not receive support from any organization for the submitted work.

Author information

Authors and Affiliations

  1. Faculty of Medicine, University of Ruhuna, Galle, Sri Lanka

    Achala Liyanage, G. Liyanage, V. De Silva & S. Lekamwasam

  2. Dermatology Department, National Hospital of Sri Lanka, Colombo, Sri Lanka

    J. Akarawita & C. Gunasekera

  3. Fukuoka University, Fukuoka, Japan

    S. Imafuku

Authors
  1. Achala Liyanage
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  2. G. Liyanage
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  3. V. De Silva
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  4. J. Akarawita
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  5. C. Gunasekera
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  6. S. Imafuku
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  7. S. Lekamwasam
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Contributions

All authors contributed to the study conception and design. The material preparation was done by Dr. Achala Liyanage and Dr. Gayani Liyanage. Data collection done by Dr. Achala Liyanage, Dr. Janaka Akarawita and Dr. Chalukya Gunasekera. The data analysis was performed by Dr. Achala Liyanage and Prof. Sarath Lekamwasam. The first draft of the manuscript was written by Dr. Achala Liyanage and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Achala Liyanage.

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Conflicts of interest

Authors declare no conflicts of interest.

Ethical approval

The study obtained ethical approval from the Ethical Review Committee of Faculty of Medicine, University of Ruhuna (Ref No. 15.02.2018:3.6) and is accordance with the 1964 Helsinki declaration.

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Liyanage, A., Liyanage, G., De Silva, V. et al. Validation of psoriasis disability index (PDI) questionnaire Sinhala version. Arch Dermatol Res 314, 61–69 (2022). https://doi.org/10.1007/s00403-021-02210-5

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  • DOI: https://doi.org/10.1007/s00403-021-02210-5

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