Assessment of the dimensions, construct validity, and utility for rheumatoid arthritis screening of the COPCORD instrument.

This study aims to evaluate the structural validity of the Community-Oriented Program for the Control of Rheumatic Diseases (COPCORD) core instrument as a screening tool for rheumatoid arthritis (RA) by means of assessing the existence of domains in the questionnaire. The Mexican version of the COPCORD instrument was applied to individuals over18 years of age in five regions of the country through a probabilistic/convenience household survey. Clinical confirmation of RA diagnosis was used. The variables analyzed included self-reported comorbidities and manifestations of the disease, as well as sociodemographic characteristics. The statistical approach was based on polychoric exploratory factor analysis and confirmatory factor analysis by means of probit structural equation models. A total of 19,213 subjects were included in the analysis. The average age for the total sample was 42.89 years old; 40.64 % of the subjects were older than 45 years of age and 20.42 % older than 55. More than 80 % of the variation was related to three underlying factors: recent pain, historical pain, and disability. The findings verified the usefulness of the COPCORD instrument as a screening tool for RA. The results also allowed to characterize how the variation in terms of manifestations of the disease could be accounted for diagnosing the disease in the Mexican context and examined the capabilities of the instrument to measure correctly the main characteristics of patients suffering from RA.