Comorbidities, rather than the effects of inflammatory joint disease, may be why some patients with rheumatoid arthritis remain functionally disabled despite effective treatment for their arthritis.
This study included 380 RA patients from an outpatient clinic with a wide range of disease activity, disease duration, and comorbid conditions, according to Dr. Helga Radner and her associates from the Medical University of Vienna.
The study was based on serial measurements taken from more than 1,600 patient visits between June 2007 and July 2008. Physical disability was measured using the HAQ (Health Assessment Questionnaire) disability index. The Charlson Comorbidity Index (CCI), adjusted for age, was used to assess comorbidity burden, with differing weights given to comorbid conditions such as myocardial infarction (weight = 1), diabetes mellitus with complications (weight = 2), or AIDS (weight = 6).
Analysis of variance indicated a consistent increase in physical disability with increasing comorbidity burden (P less than .01), even after adjustment for disease activity, sex, or disease duration (Ann. Rheum. Dis. 2010 [doi:10.1136/ard.2009. 118430]).
The influential effect of comorbidities on functional disability in patients with RA was seen across all levels of RA disease activity, as measured by the CDAI (Clinical Disease Activity Index). For RA patients with low or moderate/high disease severity, having one or more comorbidities added to the levels of functional disability, “reflecting the well-known contribution of [RA] disease activity to impairment of physical function,” Dr. Radner and her associates said. However, even patients who were thought to be in remission for RA showed significant increases in functional disability when comorbidities were present (P less than .01).
“Based on our analyses, the average HAQ in a group of patients with several comorbid conditions would be somewhere around 0.6, even if the best possible treatment was used. This floor effect of functional improvement is an important aspect when evidence of therapeutic efficacy needs to be provided, such as for reimbursement of interventions,” the authors wrote.
Disclosures: Dr. Radner and her associates report having no conflicts of interest.