A systematic review of the cost-effectiveness literature for insulin pumps conducted by the Assessment group found 11 publications. Except for one study which developed a relatively simple Markov model and another in which the model was not reported, all publications used the Centre for Outcomes Research (CORE) model. Three studies that were performed in the United Kingdom and took the health service perspective reported incremental cost-effectiveness ratios (ICERs) for continuous subcutaneous insulin infusion (CSII) therapy compared with multiple daily injections (MDI) therapy of 11,500 pounds sterling, 26,300 pounds sterling, and 32,800 pounds sterling per quality-adjusted life year (QALY) gained. In the cost-effectiveness studies, the most common assumed improvement in glycosylated haemoglobin (HbA1c) levels with CSII therapy compared with MDI therapy was 1.2%.
The base-case analysis with a reduction of HbA1c levels of 0.9% and a severe hypoglycaemic event rate of 18.7 episodes per 100 person years reduced by 50%, over a time horizon of 50 years, produced an ICER of 37,712 pounds sterling per QALY gained for CSII compared with MDI therapy. Changing the reduction in the rate of severe hypoglycaemia events to 0% or 75% did not change the ICER significantly. With the higher baseline rate of severe hypoglycaemia assumed in the manufacturers' submission, a 50% reduction, and baseline HbA1c levels reduced to 7.9% from a baseline of 8.8%, the ICER was 36,587 pounds sterling per QALY gained. When a greater reduction in HbA1c levels of 1.4% was assumed, with no reduction in severe hypoglycaemic event rates, the ICER was 24,720 pounds sterling per QALY gained. In the cohort with good glycaemic control, when there was assumed to be no improvement in HbA1c levels but the severe hypoglycaemic event rate was 134 per 100 person years, the ICER was 273,992 pounds sterling per QALY gained for a 50% reduction and 152,058 pounds sterling per QALY gained for a 75% reduction in severe hypoglycaemia rate. Avoidance of severe hypoglycaemic events can lead to quality of life gains by avoiding the disutility of the event itself and because of the reduced fear of such events. In the scenario with a 0.9% decrease in HbA1c from a baseline of 8.8% and a 50% reduction in the rate of severe hypoglycaemia events from that in the manufacturers' submission, which was associated with an ICER of 36,587 pounds sterling, an assumed annual 0.01 quality of life increment in the CSII arm decreased the ICER to 29,300 pounds sterling per QALY gained. When the assumed quality of life increment was 0.03, the ICER decreased to 21,000 pounds sterling per QALY gained. In the cohort with good glycaemic control, when there was assumed to be no improvement in HbA1c levels, the severe hypoglycaemic event rate was 134 per 100 person years, an annual quality of life increment of 0.05 was assumed and a reduction in the rate of severe hypoglycaemia events by 50%, the ICER was 28,600 pounds sterling per QALY gained. For the same cohort but with a 75% reduction in severe hypoglycaemia events, and an annual quality of life increment of 0.04 the ICER was approximately 31,300 pounds sterling per QALY gained.
The Committee agreed that at very high baseline HbA1c levels the decrease expected with CSII could make CSII therapy cost effective because of the avoidance of long-term complications. However, at baseline levels of less than 9.0%, CSII would only be cost effective if an additional quality of life benefit was assumed. This benefit could be derived from the avoidance of the fear of hypoglycaemia as well as from other quality of life improvements associated with the use of insulin pumps themselves which were not captured in the base-case economic modelling. The Committee judged that when a plausible small quality of life benefit is assumed, CSII would be cost effective at a baseline HbA1c level of 8.5% or above, and therefore concluded that CSII therapy is recommended as a treatment option for adults with type 1 diabetes mellitus whose HbA1c levels have remained high (that is, at 8.5% or above) on MDI therapy (including, if appropriate, the use of long-acting insulin analogues) despite a high level of care.
Refer to Section 4 of the original guideline document for details of the economic analyses provided by the manufacturers, the Assessment Group, and the Appraisal Committee considerations.