Validity and reliability of the Turkish version of the Patient Health Questionnaire-8 for patients with systemic sclerosis

Abstract

Objective: Depressive symptoms harm the quality of life, with a higher prevalence in patients with rheumatological diseases. The Patient Health Questionnaire-9 (PHQ-9) used for depression evaluation in patients with systemic sclerosis (SSc) has been validated in Turkish. However, the Turkish version of PHQ-8, a shorter form of PHQ-9, has not been validated. This study aimed to evaluate the reliability and validity of PHQ-8 in Turkish patients with SSc. Methods: Permission was obtained from the authors who developed the original scale. The testing procedure for translation and cultural adaptation was carried out according to the following steps: preparation, forward translation, reconciliation, back-translation/back-translation review, harmonization, finalization, and proofreading. Patients’ demographic parameters, comorbidities, education levels, organ involvement, Health Assessment Questionnaire (HAQ), Scleroderma Health Assessment Questionnaire (SHAQ), Short form-36 (SF-36), and Multidimensional Assessment of Fatigue (MAF) results were recorded. Construct validity, test-retest reliability, and internal consistency were evaluated in 43 patients with SSc. Results: Despite some linguistic changes, the questionnaire had satisfactory content validity. There were moderate-to-strong correlations between the Turkish version of PHQ-8 and SHAQ consisting of visual analog scale (rs=0.6 to 0.7) and HAQ disability (rs=0.5), the subscales of SF-36 (rs=0.6 to 0.8), and MAF (rs=0.7). The internal consistency (Cronbach’s alpha) of the questionnaire was 0.98, with corrected item-to-total correlations of >0.40, and an intraclass correlation coefficient of 0.947 for the total score (Intraclass correlation coefficient=0.947, 95% confidence interval, 0.817-0.985). Conclusion: The Turkish version of PHQ-8 could be used to evaluate patients with SSc with satisfactory construct validity and sufficient reliability.