Mapping chronic liver disease questionnaire scores onto SF-6D utility values in patients with primary sclerosing cholangitis Evangelos Kalaitzakis 1,2,3 • Maria Benito de Valle 2 • Monira Rahman 4 • Bjo ¨rn Lindkvist 2 • Einar Bjo ¨rnsson 5 • Roger Chapman 4 • Nick Kontodimopoulos 3 Accepted: 10 October 2015 / Published online: 15 October 2015 Ó Springer International Publishing Switzerland 2015 Abstract Purpose The chronic liver disease questionnaire (CLDQ) is a frequently used liver-specific quality of life instrument, but it does not provide information on preference-adjusted health status, which is essential for cost-utility analysis. We aimed to develop a mapping function deriving utilities from the CLDQ in primary sclerosing cholangitis (PSC). Methods Short form-6D (SF-6D) utilities were calculated from SF-36 data collected in a recent prospective study in which unselected patients with PSC also completed the CLDQ. Ordinary least squares (OLS), generalized linear, median, and kernel regression analyses were employed to devise a mapping function predicting utilities. This was validated in three random subsamples of the cohort and in a separate sample of PSC patients following liver trans- plantation. Adjusted R 2 and root-mean-square error (RMSE) as well as Pearson’s r coefficients and mean absolute errors between predicted and observed values were used to determine model performance. Results Decompensated liver disease and fatigue, sys- temic symptoms, and emotional distress, assessed with the CLDQ, were related to worse SF-6D utilities. The final OLS prediction model explained 66.3 % of the variance in the derivation sample. Predicted and observed utilities were strongly correlated (r = 0.807, p \ 0.001), but the mean absolute error (0.0604) and adjusted RMSE (10.6 %) were of intermediate size. Similar model characteristics were observed after employment of generalized linear and median regression models and at validation. Conclusions A model has been constructed, showing good validity predicting SF-6D utilities from CLDQ scores at the group level in PSC. Further testing is required to externally validate the model. Keywords Primary sclerosing cholangitis Á Health- related quality of life Á Chronic liver disease questionnaire Á SF-6D Á Health utilities Á Mapping Á Liver transplantation Abbreviations PSC Primary sclerosing cholangitis HRQL Health-related quality of life CLDQ Chronic liver disease questionnaire SF-36 Short form-36 health survey SD Standard deviation OLS Ordinary least squares RMSE Root-mean-square error GLM Generalized linear model MID Minimally important difference PBC Primary biliary cirrhosis & Evangelos Kalaitzakis kalvag@hotmail.com 1 Digestive Disease Center, Copenhagen University Hospital/ Bispebjerg, University of Copenhagen, 2400 Copenhagen, Denmark 2 Institute of Internal Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden 3 Faculty of Social Sciences, Hellenic Open University, Patras, Greece 4 Department of Gastroenterology, John Radcliffe Hospital, Oxford, UK 5 Department of Internal Medicine, Landspitali University Hospital, Reykjavik, Iceland 123 Qual Life Res (2016) 25:947–957 DOI 10.1007/s11136-015-1161-x