VALUING PREFERENCES FOR THE PROCESS AND OUTCOME OF CLINICAL GENETICS SERVICES: A PILOT STUDY

Purpose: The nature of the outcome attribute for clinical genetics services (CGSs) (informed decision-making), poses a methodological challenge when designing a stated choice experiment. This pilot study aimed to identify if a hybrid conjoint analysis-discrete choice experiment can be used to quantify the relative importance of process and outcome attributes associated with CGSs. 

Method: An on-line hybrid conjoint analysis (CA)-discrete choice experiment (DCE) was designed to elicit the preferences of a purposive sample of CGS users and members of the public to (i) identify service attributes (n=13) perceived to facilitate informed decision-making; (ii) to determine relative preferences for six attributes (5 process; 1 outcome - ability to make an informed decision). A systematic review of outcome measures (n=67), semi-structured interviews/focus groups (n=52 patients/ healthcare professionals) and Delphi survey (n= 72 patients and 115 service providers) informed the attributes and levels. Respondents also rated their preferred level of involvement in decision making based on a clinical scenario and their prior experience of CGSs. A three-step approach was taken to analyse the CA and DCE data which involved linking the data from the two stated preference studies using hierarchical information integration and using ordered logit and random effects probit models. Marginal willingness-to-pay (WTP) values (and 95% CI) were calculated.

Result: The data analysis used the pooled CGS user and public samples (n=37; 76% female; mean age: 44 years; 95% in paid employment).  The sample comprised respondents with (51%) and without (49%) experience of CGS. The majority (89%) of respondents indicated they wanted some input into decision-making. The CA showed that 11 of the 13 attributes were positively associated with the ability to make an informed decision. The DCE indicated respondents favoured a CGS with some pre-consultation contact, short waiting times and one which would improve their ability to make an informed decision. Estimated WTP values were: service location (£2953; 95% CI: -779 to 15,110); degree of follow-up contact (-£1620; -7285 to 851); reduction (by one month) in waiting time (-£1014; -3656 to -567); having some pre-consultation contact (£8664; 2674 to 33029); improved ability to make an informed decision (£1698/unit increase on a 9-point scale; 609 to 7429).

Conclusion: This study supported that a hybrid stated preference experiment offers a practical solution to understanding preferences in complex situations.