Psychometric Evaluation of the Tagalog Version of Psoriatic Arthritis Quality of Life Questionnaire

Abstract

Background. Psoriatic arthritis (PsA) is a potentially destructive inflammatory arthritis among individuals with psoriasis which may lead to disability and poor quality of life. The Psoriatic Arthritis Quality of Life (PsAQoL) questionnaire is an instrument developed to assess the true impact of PsA on the overall lives of patients. There are 32 language versions, 12 in developing countries. The Tagalog version has been translated and tested for face and content validity but has not been fully validated psychometrically. 

Objective. This study aimed to evaluate the psychometric properties of the Tagalog version of the PsAQoL to assess its reliability and consistency.

Methods. This is a prospective validation study involving 47 patients with PsA from June to August 2023. The psychometric properties tested were internal consistency (Cronbach’s alpha coefficients), test-retest reliability, convergent validity (Spearman’s rank correlation), and known group validity (Mann-Whitney U Test or KruskalWallis One-Way Analysis of Variance). 

Results. The PsAQoL on both week 0 and week 2 had Cronbach’s alpha coefficients of 0.926 indicating high internal consistency. Test-retest reliability was 0.929, which demonstrates excellent reliability and low level of random measurement error. The PsAQoL scores highly correlated with the Health Assessment QuestionnaireDisability Index (r=0.754, p<0.001), which demonstrates convergent validity. However, there was no significant correlation with the pain scale (r=0.225, p=0.128). No significant differences in PsAQoL scores were found between participants for demographic factors. However, there was a significant difference in self-reported health scores (p=0.015). This demonstrates the ability of the Tagalog PsAQoL to detect meaningful differences.

Conclusion. The Tagalog version of the PsAQoL demonstrates excellent psychometric properties and is recommended for monitoring of Tagalog-speaking patients with psoriatic arthritis in healthcare settings.