Modelling cost effectiveness and cost utility of sequential DMARD therapy including leflunomide in rheumatoid arthritis in Germany

Abstract

To quantify direct costs of medication and cost of illness (according to functional capacity) for patients with rheumatoid arthritis (RA) in Germany, allowing further use in a health economic evaluation of sequential therapy with disease-modifying antirheumatic drugs (DMARDs) in specialised, i.e. rheumatological, care in Germany. The analysis was conducted from the societal perspective in Germany using a modelling approach, which was based on secondary analysis of existing data and on data from a sample of 583 patients from the German rheumatological database of 1998. Functional capacity was defined by the Hannover Functional Ability Questionnaire (HFAQ) scores. Costs were calculated from resources utilised and patients' work capacity. Direct costs consisted of outpatient medical services, inpatient treatment, long-term care and rehabilitation treatment. Indirect costs incurred by sick leave and premature retirement were quantified according to the human-capital approach. Average total direct costs (year 1998-2001 values) per patient per year for continuous treatment with the selected DMARDs comprising costs for drugs, monitoring and treatment of adverse drug reactions (ADRs) were highest for intramuscular gold (sodium aurothiomalate) [euro 2106 (euro 1 approximately equal to $US 0.91; average of the period from 2000 through 2001)] followed by leflunomide (euro 2010), azathioprine (euro 1878), sulfasalazine (euro 1190), oral methotrexate (euro 708), and lowest for the antimalarials chloroquine/hydroxychloroquine (euro 684). There were additional yearly costs for RA-related non-DMARD medication of euro 554 per patient, including management of ADRs. Mean cost of illness (year 1998 values) excluding medication cost amounted to euro 17,868 per RA patient per year. Annual costs increased with increasing disability, i.e. decreasing functional capacity, of RA patients from euro 6029 per patient with more than 94% of functional capacity to euro 28,509 per patient with <20% of functional capacity. In general, there was a predominance of indirect costs in each of the categories of functional capacity, ranging between 74% and 87% of total (direct and indirect) annual costs per RA patient. Annual direct costs increased from euro 811 to euro 7438 per patient with increasing disability. Inpatient treatment was the predominant component of direct costs. Patients in the worst category (<20%) of function experienced hospital costs that were 6.5 times higher than those of patients in the best category (>94%). On the basis of the data presented it can be concluded that the results of this investigation are typical for patients in rheumatological care in Germany and can therefore be used in a health economic analysis of different DMARD sequences aimed at changing disease progression over time.