Elicitation of Health State Utilities Associated with Varying Severities of Flare in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is characterised by fluctuating periods of minimal disease activity and ‘flare’. Flare is an important outcome variable impacting the economic and humanistic burden of SLE. The objective of this study was to obtain population-based utility values for varying severities of flare to measure the impact on health-related quality of life (HRQoL). Six health states (HS) for varying severities of flare were developed based on literature, patient blogs, and interviews with patients (n=12), rheumatologists (n=7) and nurses (n=2). HS were verified by independent clinical experts (n=6) and pilot interviews (n=10, UK). HS were evaluated using the time-trade-off (TTO) method during face-to-face interviews with a minimum representative sample (n=100) of the general population, per-country, in Australia, Canada, France, Japan, Spain and the UK. Visual Analog Scale (VAS) scores were obtained to validate TTO scores. TTO scores were converted into utility values. The highest mean TTO utility scores (range 0.66-0.82) were observed for the anchor HS (minimal disease activity) across all countries. All flare HS were associated with a disutility compared with the anchor HS: mild flare HS (0.55-0.71), moderate flare HS (0.38-0.53), severe renal flare HS (0.33-0.45), severe Central Nervous System (CNS) flare HS (0.30-0.45) and severe generalised flare HS (0.19-0.33). Significant differences were reported between the anchor state and each flare state across all countries (p<0.05). Mean VAS scores followed the same trend. The severe generalised flare HS received the lowest mean TTO utility score across all six countries suggesting that the perceived day-to-day impact of a severe generalised flare was greater than a severe CNS or severe renal flare. These results show that a decrease in utility, representing a detrimental impact on HRQoL, was observed with increasing severity of flare. These results could be applied in cost-utility analyses for interventions for SLE.