OBJECTIVES : In cost-utility analyses, quality-of-life (QoL) is measured using health state utility valuations (HSUV). However, people with inherited and long-term health conditions may adapt to their given health state and adjust their expectations (i.e., the “disability paradox”; Albrecht and Devlieger, 1999). HSUVs elicited from these populations may be higher than those derived from members of the general public. This study aimed to review existing literature on such disease state adaptation (DSA) and consider approaches to ensure that limitations of existing QoL metrics do not further impact the evaluation of novel health technologies.

METHODS : A systematic literature review (SLR) of electronic medical literature databases, including MEDLINE®, Web of Science, and Cochrane Library, was conducted (03/2004-03/2019). Relevant conferences were also queried (from 2016). Two reviewers independently double-screened studies and extracted data according to pre-defined criteria.

RESULTS : Of 882 titles and abstracts screened, 38 studies were included for review. DSA was most commonly assessed in chronic conditions, such as rheumatoid arthritis and tinnitus. Two main experiment paradigms were response shift (n=18), 11 of which found evidence of DSA, and adaptation task (n=15), of which 9 reported DSA. The remaining five studies employed other experimental designs, among which 3 reported DSA. Overall, DSA was observed in 23/38 (~60%) studies; the remaining studies found either no or insufficient evidence.

CONCLUSIONS : This SLR shows that DSA is common among patients with serious chronic diseases. Therefore, these patient-reported HSUVs may be higher than valuations of health states derived from members of the general public. Recent evidence (Carlsson et al., 2017) suggests that DSA might exist in haemophilia and warrants further research. The impact of DSA on HSUVs should be characterised within cost-utility analyses of novel treatments with transformative impact on patients’ lives, such as gene therapies.