Quality of Life in Adult Patients with Growth Hormone Deficiency : Bridging the gap between clinical evaluation and health economic assessment
Abstract: The goals of this thesis are to evaluate quality of life (QoL) in adult patients with growth hormone deficiency (GHD) in relation to population normative data, to construct a preference-weighted index (utility) from a disease-specific QoL measure and to assess it in a clinical context.The study included samples from the general population and patients with GHD from four European populations: England & Wales, the Netherlands, Spain and Sweden. The country-specific patient cohorts were retrieved from KIMS (Pfizer International Metabolic Database). A questionnaire was developed that contained items from existing QoL questionnaires including, among others, Quality of Life Assessment in Growth Hormone Deficiency in Adults (QoL-AGHDA) and the EQ-5D. The QoL-AGHDA is a disease-specific measure for use in adults with GHD. The EQ-5D is a generic instrument which describes health states for which country-specific preference-based weights are available. Thus, it was possible to generate preference-weighted indices (utilities) based on data generated by both instruments. This thesis reports QoL-AGHDA normative values for the populations of England & Wales, the Netherlands, Spain and Sweden, and confirms the extent of QoL impairment in patients with GHD in comparison with the general population. Long-term GH replacement resulted in sustained improvements in overall QoL towards normative country-specific values, as well in most of the dimensions that were impaired before treatment. For use in health economic evaluations, models for generating utilities (QoL-AGHDAutility) from QoL-AGHDA were developed. It is believed that these models may facilitate medical decision making, given that they provide a tool for obtaining utilities in the absence of directly collected preference-weighted indices.QoL-AGHDAutility effectively monitored treatment effects in patients with GHD. Moreover, this study confirmed a QoL-AGHDAutility deficit before treatment and a gain after starting GH replacement. The novel aspect of the present approach was to apply preference-weighted indices derived from a disease-specific measure to assess QoL in the clinical context, together with patient demographic and clinical characteristics. The robustness of this analysis is reinforced by the fact that utilities in both general and patient populations were generated using the same methodology.
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