BACKGROUND: To our knowledge, adjustment for baseline imbalances in costs has never been performed in trial-based cost-effectiveness analyses. METHODS: We used data from a clinical trial performed in the Netherlands comparing two outpatient psychotherapies: schema-focused therapy (SFT) versus transference-focused psychotherapy (TFP). Costs were assessed with a cost interview. Outcome was the proportion of recovered patients measured with the Borderline Personality Disorder Severity Index (BPDSI-IV). We used three methods to adjust the costs for baseline differences: (i) mean difference adjustment, calculating total costs after baseline by adjusting the difference between groups with the difference of the mean baseline costs; (ii) delta adjustment, calculating the individual differences between patient baseline and the subsequent measurements (concerning incremental costs, this is the same as mean difference adjustment); and (iii) regression-based adjustment, adjusting total costs with a regression model, with total costs as the dependent variable and baseline costs as the independent variable. RESULTS: Mean baseline costs were 3339 euros for SFT and 4238 euros for TFP, a mean difference of 899 euros. Total unadjusted follow-up costs were 30822 euros for SFT and 36812 euros for TFP. The fraction of recovered patients was 45% for SFT and 24% for TFP. Cost-effectiveness acceptability curves show that mean difference and delta adjustments are different from the regression-based methods. CONCLUSIONS: Although the routine starting point of an analysis should always be an unadjusted analysis of the cost effectiveness, a baseline difference between treatment groups should be adjusted for. This should be done by reported patient characteristics or, when these are not sufficiently present, by baseline costs as a substitute. This adjustment should be carried out most preferably with a regression-based method.
BACKGROUND: To our knowledge, adjustment for baseline imbalances in costs has never been performed in trial-based cost-effectiveness analyses. METHODS: We used data from a clinical trial performed in the Netherlands comparing two outpatient psychotherapies: schema-focused therapy (SFT) versus transference-focused psychotherapy (TFP). Costs were assessed with a cost interview. Outcome was the proportion of recovered patients measured with the Borderline Personality Disorder Severity Index (BPDSI-IV). We used three methods to adjust the costs for baseline differences: (i) mean difference adjustment, calculating total costs after baseline by adjusting the difference between groups with the difference of the mean baseline costs; (ii) delta adjustment, calculating the individual differences between patient baseline and the subsequent measurements (concerning incremental costs, this is the same as mean difference adjustment); and (iii) regression-based adjustment, adjusting total costs with a regression model, with total costs as the dependent variable and baseline costs as the independent variable. RESULTS: Mean baseline costs were 3339 euros for SFT and 4238 euros for TFP, a mean difference of 899 euros. Total unadjusted follow-up costs were 30822 euros for SFT and 36812 euros for TFP. The fraction of recovered patients was 45% for SFT and 24% for TFP. Cost-effectiveness acceptability curves show that mean difference and delta adjustments are different from the regression-based methods. CONCLUSIONS: Although the routine starting point of an analysis should always be an unadjusted analysis of the cost effectiveness, a baseline difference between treatment groups should be adjusted for. This should be done by reported patient characteristics or, when these are not sufficiently present, by baseline costs as a substitute. This adjustment should be carried out most preferably with a regression-based method.
Authors: Mandy van den Brink; Wilbert B van den Hout; Anne M Stiggelbout; Hein Putter; Cornelis J H van de Velde; Job Kievit Journal: Int J Technol Assess Health Care Date: 2005 Impact factor: 2.188
Authors: Arnoud Arntz; Marije van den Hoorn; Jurgen Cornelis; Roel Verheul; Wies M C van den Bosch; Arthur J H T de Bie Journal: J Pers Disord Date: 2003-02
Authors: Wen Wan; Aviva G Nathan; M Reza Skandari; Parmida Zarei; Mark W Reid; Jennifer K Raymond; Elbert S Huang Journal: Diabetes Care Date: 2019-06-12 Impact factor: 19.112
Authors: Michael Groff; Eric Latimer; Ridha Joober; Srividya N Iyer; Norbert Schmitz; Sherezad Abadi; Amal Abdel-Baki; Nicola Casacalenda; Howard C Margolese; G Eric Jarvis; Ashok Malla Journal: Schizophr Bull Date: 2021-03-16 Impact factor: 9.306
Authors: Elizabeth N Mutubuki; Mohamed El Alili; Judith E Bosmans; Teddy Oosterhuis; Frank J Snoek; Raymond W J G Ostelo; Maurits W van Tulder; Johanna M van Dongen Journal: BMC Health Serv Res Date: 2021-05-19 Impact factor: 2.655
Authors: L Esther de Graaf; Sylvia A H Gerhards; Silvia Maa Evers; Arnoud Arntz; Heleen Riper; Johan L Severens; Guy Widdershoven; Job F M Metsemakers; Marcus J H Huibers Journal: BMC Public Health Date: 2008-06-30 Impact factor: 3.295
Authors: Henny J Wansink; Ruben M W A Drost; Aggie T G Paulus; Dirk Ruwaard; Clemens M H Hosman; Jan M A M Janssens; Silvia M A A Evers Journal: BMC Health Serv Res Date: 2016-07-07 Impact factor: 2.655