The use and context of the term "multimorbidity" in rheumatoid arthritis: a systematic literature review.

This systematic literature review aimed to analyse term(s) describing co-existing conditions in rheumatoid arthritis (RA) literature, informing the need for an operationalised definition of multimorbidity. Articles discussing RA with multimorbidity, published 1946 until August 2020, were identified. The primary outcome was use and/or definition of "multimorbidity" in RA. Information extracted included: term(s) defining co-existing conditions; use of comorbidity/multimorbidity score; use of "index disease" to describe RA (more applicable to comorbidity than multimorbidity). Thirty-nine articles were included. Eight articles used the term "multimorbidity"; 18 used "comorbidity." 12 used both terms, seven synonymously. One used no term. Fourteen articles fully defined the term. The number of co-existing conditions ranged from one-121. Twelve articles used a comorbidity/multimorbidity score. Four articles described RA as the "index disease". Our results demonstrate inconsistent use of the term multimorbidity. Improved assessment of multimorbidity is indicated in RA patients, including an operationalised use and definition.