Objective: Chikungunya virus is spread by mosquitos and causes a debilitating chronic arthritis that has no standard treatment to date and no specific measures of disease activity. The objective of this expert group was to develop a measure of chikungunya arthritis that would be useful for clinical trials and patient care.
Methods: A group of rheumatologists and biostatisticians experienced in the clinical and pathological mechanisms of chikungunya evaluated component measures for inclusion in a chikungunya arthritis disease activity score (CHIK-DAS). Utilizing data from a Colombian cohort of 158 chikungunya arthritis patients, linear regression identified components that were independently associated with patient reported outcomes assessing disability, pain, physical and mental quality of life and mobility. A preliminary instrument was developed using multiple imputation and regression backward selection. Cutoffs for grading disease severity were determined.
Results: Stiffness, ankle tenderness, and a 30 tender joint count that included the 28 joints traditionally included in the Disease Activity Score-28 were selected in a regression model predicting a composite of five patient reported outcomes. A CHIK-DAS scoring formula was developed through a weighted combination of these selected variables. In comparison to the DAS-28, the CHIK-DAS had improved predictive value for a composite outcome of disability, pain, physical and mental quality of life and mobility. Disease activity cutoffs were defined for remission (<40), mild (40-49.99), moderate (50-59.99) and severe (60+) disease.
Conclusion: The CHIK-DAS is a chikungunya specific measure of disease activity that includes the DAS-28 with the addition of ankle tenderness and a stiffness item that are prominent components of chikungunya arthritis. CHIK-DAS may be used as a specific measure of disease activity in chikungunya arthritis in clinical trials and patient care. This metric needs further validation in additional cohorts.
Keywords: Arthritis; Chikungunya; Clinical trials; Disability; Disease severity score; Pain; Quality of life.