Preference-based utility weights for the Individualized Neuromuscular Quality of Life Questionnaire (INQoL), with a focus on non-dystrophic myotonia (NDM).

INTRODUCTION: The Individualized Neuromuscular Quality of Life Questionnaire (INQoL) is used to measure quality of life in neuromuscular disorders such as non-dystrophic myotonia (NDM). Here we report methods to estimate utilities, with a focus on NDM, from this questionnaire based on two preference elicitation exercises. METHODS: Eight items from the INQoL were selected with input from three neuromuscular disorder clinical experts with expertise in treating NDM. A discrete choice experiment (DCE) survey of UK general public respondents (n = 508) described outcomes defined by the INQoL items. The same 8 items were also valued using time trade-off (TTO) face-to-face interviews (n = 200). A hybrid regression modelling approach combined both datasets to inform the utility weights. RESULTS: Hybrid modelling of DCE and TTO data in conjunction improved out-of-sample predictive accuracy. The selected INQoL utility model indicates substantial disutility associated with all eight dimensions of health, with the greatest losses associated with subjective items such as pain and depression. DISCUSSION: The hybrid modelling approach allows us to combine data from the two methodologies and maximize the information from each to inform the utility weights for the INQoL. The TTO is the more conventional valuation method, but combined with the larger DCE study produced better descriptive coverage. This is a relatively novel method for estimating weights which we think is particularly well suited to economic evaluations of orphan drugs.

Stressors and common mental disorder in informal carers--an analysis of the English Adult Psychiatric Morbidity Survey 2007.

This study investigates potential explanations of the association between caring and common mental disorder, using the English Adult Psychiatric Morbidity Survey 2007. We examined whether carers are more exposed to other stressors additional to caring--such as domestic violence and debt--and if so whether this explains their elevated rates of mental disorder. We analysed differences between carers and non-carers in common mental disorders (CMD), suicidal thoughts, suicidal attempts, recent stressors, social support, and social participation. We used multivariate models to investigate whether differences between carers and non-carers in identifiable stressors and supports explained the association between caring and CMD, as measured by the revised Clinical Interview Schedule. The prevalence of CMD (OR=1.64 95% CI 1.37-1.97), suicidal thoughts in the last week (OR=2.71 95% CI 1.31-5.62) and fatigue (OR=1.33 95% CI 1.14-1.54) was increased in carers. However, caring remained independently associated with CMD (OR=1.58 1.30-1.91) after adjustment for other stressors and social support. Thus caring itself is associated with increased risk of CMD that is not explained by other identified social stressors. Carers should be recognized as being at increased risk of CMD independent of the other life stressors they have to deal with. Interventions aimed at a direct reduction of the stressfulness of caring are indicated. However, carers also reported higher rates of debt problems and domestic violence and perceived social support was slightly lower in carers than in non-carers. So carers are also more likely to experience stressors other than caring and it is likely that they will need support not only aimed at their caring role, but also at other aspects of their lives.