Factors associated with disease severity in Mexican patients with rheumatoid arthritis

To investigate clinical, demographic, laboratory, and behavioral variables associated with disease severity in rheumatoid arthritis (RA).

A case-control study was carried out in a tertiary care center. Participants were RA patients, 16-65 years of age, with a disease duration of > or = 2 years. Selection criteria were established in advance. The sample size was calculated taking into account the prevalence of a low formal education level (< 6 years of school) in a sample of 60 patients. Controls for each case were paired according to age, sex, rheumatoid factor, and disease duration for a case/control ratio of 1:1.8. Cases were defined as those patients having at least two of the following: failure to respond to > or = 3 disease modifying anti-rheumatic drugs, score > or = 3/10 on the Disability Index of the Health Assessment Questionnaire, and disease severity > or = 4/10 as judged by the treating physician on a visual analogue scale. Controls were obtained from the same group but without such characteristics. All of the clinical charts were blindly evaluated for the clinical, demographic, laboratory, and behavioral variables. Descriptive statistics, univariate and multivariate analysis, odds ratios (OR) and 95% confidence intervals (95% CI) were calculated.

We studied 46 cases and 82 controls. Univariate analysis showed that severity was associated with a low level of formal education (OR 3.15, CI 1.38-7.13), use of non-conventional therapy (OR 2.7, CI 1.34-5.49), treatment with oral steroids (OR 2.6, CI 1.28-6.8), compliance, and disease duration before a confirmed diagnosis of RA. These variables remained in the multivariate model. A low hemoglobin level and an increased platelet count were the biological variables associated with severity.

The evaluation of RA must be conducted in a socio-cultural context since this is in some way linked to disease severity.