METHODS: A novel research instrument known as the rheumatoid arthritis knowledge assessment scale (RAKAS) which consisted of 13 items, was formulated by a rheumatology panel and used for this study. This study was conducted in rheumatology clinics of three tertiary care hospitals in Karachi, Pakistan. The study was conducted in March-April 2018. Patients were recruited using a randomized computer-generated list of appointments. Sample size was calculated based on item-to-respondent ratio of 1:15. The validities, factor structure, sensitivity, reliability and internal consistency of RAKAS were assessed. The study was approved by the institutional Ethics Committee.

RESULTS: A total of 263 patients responded to the study. Content validity was 0.93 and response rate was 89.6%. Factor analysis revealed a 3-factor structure. Fit indices, namely normed fit index (NFI), Tucker Lewis index (TLI), comparative fit index (CFI) and root mean square of error approximation (RMSEA) were calculated with satisfactory results, that is, NFI, TLI and CFI > 0.9, and RMSEA 19 and difficulty index <0.95. Sensitivity and specificity of RAKAS were above 90%. The tool established construct and known group validities.