Instruments to assess comorbidity are based on (i) review of medical charts (e.g. Charlson index), (ii) pharmacy data (e.g. RxRisk score), (iii) medical interview (e.g. Cumulative Index Illness Rating Scale, CIRS), (iv) self report (e.g. Self-Administered Comorbidity Questionnaire, SCQ), or (v) a screening tool or diagnostic test for a specific disease (e.g. Center for Epidemiologic Studies Depression scale, CES-D). A further distinction concerns simple counts of the number of diseases versus indices that weigh a range of diseases.
The characteristics and relative advantages of these instruments will be discussed. The purpose of the study and feasibility are major criteria for selecting a specific instrument.
The use of these instruments will be illustrated with studies on the impact of comorbidity on mortality, functioning, and medical management of rheumatic diseases.
Disclosure of Interest None Declared