Validity and psychometric characteristics of the self-administered comorbidity questionnaire in patients with psoriatic arthritis

The study aimed to translate and cross-culturally adapt the self-comorbidity questionnaire (SCQ) into Turkish and investigate the validity and reliability of SCQ and its modified version (mSCQ) in psoriatic arthritis (PsA). Psoriatic arthritis quality of life (PsAQoL) and short form 36 (SF-36) were used to assess the quality of life. The physical disability was evaluated with the health assessment questionnaire (HAQ). The reliability of the SCQ scale was assessed by test–retest reliability. For construct validity, the correlations of SCQ with the HAQ, SF-36, PsAQoL, age, body mass index (BMI), disease duration, disease activity in psa (DAPSA), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Psoriasis Area and Severity Index (PASI), dactylitis and enthesitis were evaluated. The mSCQ was also used by removing the items related to rheumatic conditions. For the test–retest reliability of the Turkish version of SCQ, the intraclass correlation coefficient was 0.965, p < 0.001. The SCQ and mSCQ had significant correlations with HAQ, PsAQoL, some subscales of SF-36, and age (p < 0.05), but not with disease duration, BASDAI, PASI and dactylitis (p > 0.05). Although SCQ had a low correlation with DAPSA (rho = 0.262, p = 0.031), mSCQ was not correlated with DAPSA (p > 0.05). mSCQ was significantly correlated with BMI (rho = 0.233, p = 0.016), but SCQ was not (p > 0.05). The Turkish version of SCQ had adequate reliability and validity, and the mSCQ improved the validity of the scale in patients with PsA.