Cross-culture adaptation and validation of English version of Rheumatoid Arthritis Knowledge Assessment Scale (RAKAS) in patients with rheumatoid arthritis

Aim: To carry out cross-culture adaptation and validation of the English version of Rheumatoid Arthritis Knowledge Assessment Scale (RAKAS) in patients with rheumatoid arthritis (RA). Methods: A cross-sectional study was conducted for 2 months in 2 tertiary care hospitals in Karachi, Pakistan. Sample size was calculated based on item-subject ratio. The translation was carried out using standard procedures for translation and cross-culture adaptation. The validation process included estimation of discrimination power, item difficulty index, factorial, convergent, construct and known group validities and reliability. Reliability of the scale was estimated using Kuder-Richardson Formula 20 and a value of σ² ≥ 0.6 was acceptable. SPSS v23, Remark Classic OMR v6 software and MedCalc Statistical Software v16.4.3, were used to analyze the data. The study was approved by the relevant ethics committee (IRB#NOV:15). Results: The mean score was 7.68 ± 2.52 (95% CI: 7.31-8.05) for 177 patients. The σ² = 0.601, that is, >0.6, test-retest reliability ρ =.753, P <.05. The average discrimination power = 47.27, average Item Difficulty Index = 0.557. The fit indices were acceptable in a range that established its factorial validity and average factor loading was ≥0.7 which established convergent validity. A significant association (χ² = 33.074, P <.01) between score interpretation and previous counseling by pharmacists established its construct validity. A significant association (χ² = 19.113, P <.05) between score interpretation and patient occupation established known group validity. Conclusion: The English version of RAKAS was deemed a reliable and validated tool to measure knowledge about disease in Pakistani patients with RA.