A published state-transition model (the Cardiff Diabetes Model) was adapted to estimate the cost-effectiveness of the treatment pathways, over 40 years. The model assessed three lines of treatment, which differed in second-line therapy only. The authors stated that the perspective was that of the German National Sick Fund.
The key effectiveness measures were the changes in glycated haemoglobin and body weight, and the occurrence of hypoglycaemia. The data for metformin as first-line therapy were from a systematic review; those for the two second-line therapies were from a head-to-head multinational randomised trial; and those for the third-line therapy were from a meta-analysis. Disease progression was based on evidence from the UK Prospective Diabetes Study (UKPDS) 68.
Monetary benefit and utility valuations:
The model used age-specific utility values, to which decrements were applied for complications. The initial utility values were published EQ-5D estimates for UK patients, with no complications. Most of the utility decrements were from the UKPDS 62. The relationship between the patient's fear of hypoglycaemia and utility was modelled using published equations.
Measure of benefit:
The primary measure of benefit was quality-adjusted life-years (QALYs). Future effects were discounted at a rate of 3% per annum.
The cost categories were drugs, fatal events, cases of severe hypoglycaemia, and care in hospital and by general physicians. The costs of drug therapy were based on official price lists, with weighting by the defined daily dose and average consumption. Other costs were based on published literature; German sources were generally used. The costs were presented in Euros (EUR) and adjusted to 2009 values using the consumer price index. Future costs were discounted at a rate of 3% per annum.
Analysis of uncertainty:
The authors conducted one-way, two-way, and probabilistic sensitivity analyses to assess the impact of uncertainty on the results. These results were presented in tornado charts, and a cost-effectiveness acceptability curve of the probability that the intervention was most cost-effective, over a range of willingness-to-pay thresholds.