Health state values in cancer patients and the general population: evidence from SF-6Dv2

Patient and general population health state values (HSVs) often diverge, yet evidence on the updated SF-6D is scarce. This study compared HSVs for identical SF-6Dv2 health states elicited from cancer patients and the general population using the composite time trade-off (cTTO) method.

Data were drawn from two valuation studies in Quebec, Canada: a general population sample completing an online panel (n = 1,179) and patients with breast or colorectal cancer first assessed via face-to-face interviews and subsequently online (n = 202). HSVs for 156 SF-6Dv2 health states were elicited using the cTTO method. Differences in HSVs were examined across health state severity categories using multivariate regression methods, both unadjusted and adjusted for sociodemographic characteristics. Sample-type and dimension-level analyses were also conducted.

Cancer patients reported lower mean HSVs than the general population (0.320 vs. 0.384), with a significant raw mean difference of -0.063 and a significant adjusted mean difference of -0.076. For mild and moderate health states, patients assigned slightly higher utilities, but differences were not statistically significant after adjustment, whereas for severe and worst health states, patients reported substantially lower HSVs (adjusted differences -0.330 and -0.319, respectively). Sample-type analyses showed that, on average, cancer patients assigned HSVs 0.080 lower than the general population in the full sample. In the restricted sample of pre-chemotherapy observations with complete sociodemographic data, the difference was 0.115 before adjustment and 0.107 after adjustment. Patients had larger utility decrements across all levels of social functioning (SF), mental health (MH), and vitality (VT). However, the differences were statistically significant only for the two estimable social functioning contrasts (SF4 and SF5) and one vitality level (VT3), with no statistically significant differences observed for MH. The range of estimated SF-6Dv2 HSVs was narrower for the general population (-0.353 to 1) than for cancer patients (-0.575 to 1).

Significant differences in SF-6Dv2 HSVs were observed by sample type and across health state severity levels. Economic evaluation outcomes may differ when using general population versus patient HSVs, depending on the specific health-related quality of life dimensions targeted by the intervention.