The cost-effectiveness of a pharmacogenetic test: a trial-based evaluation of TPMT genotyping for azathioprine.

BACKGROUND: Thiopurine-methyl transferase (TPMT) testing prior to the prescription of azathioprine in autoimmune diseases is one of the few examples of a pharmacogenetic test that has made the transition from research into clinical practice. TPMT testing could lead to improved prescribing of azathioprine resulting in a reduction in adverse drug reactions as well as an improvement in effectiveness. When allocating scarce resources robust evidence on cost-effectiveness is required. OBJECTIVE: This study aimed to evaluate the cost-effectiveness of a TPMT genotyping test to inform azathioprine prescribing in autoimmune diseases. The secondary aim of this study was to demonstrate the complexity of undertaking a trial-based evaluation of a pharmacogenetic test. METHODS: A prospective economic evaluation was conducted alongside the TARGET (TPMT: Azathioprine Response to Genotype and Enzyme Testing) study, a pragmatic controlled trial that randomized (1:1) patients to undergo TPMT genotyping before azathioprine (n = 167) or current practice (n = 166). Assuming the UK health service perspective and a time horizon of 4 months, resource-use and health status data were collected prospectively for all recruited patients. RESULTS: The mean incremental cost for TPMT genotyping and subsequent care pathways compared with current practice for the 4-month follow-up was -£421.06 (95% confidence interval -£925.15 to £89.75). Mean incremental quality-adjusted life-years were close to zero but negative: -0.008 (95% confidence interval -0.017 to 0.0002). Assuming a threshold of £20,000 per quality-adjusted life-year, the expected incremental net benefit of introducing the test is £256.89 (95% CI -£425.94 to £932.86). CONCLUSIONS: TPMT genotyping potentially offers a less expensive alternative than current practice, but it may also have a small but negative effect on health status. These findings are associated with significant uncertainty, and the causal effect of TPMT genotyping on changes in health status and health care resource use remains uncertain. The results from this study therefore pose a difficult challenge to decision makers.

Is shared care with annual hospital review better value for money than predominantly hospital-based care in patients with established stable rheumatoid arthritis?

OBJECTIVE: To assess the cost effectiveness and cost effectiveness acceptability of symptom control delivered by shared care (SCSC) and aggressive treatment delivered in hospital (ATH) for established rheumatoid arthritis (RA). METHODS: Economic data were collected within the British Rheumatoid Outcome Study Group randomised controlled trial of SCSC and ATH. A broad perspective was used (UK National Health Service, social support services and patients). Cost per quality adjusted life year (QALY) gained, net benefit statistics and cost effectiveness acceptability curves were estimated. Costs and outcomes were discounted at 3.5%. Sensitivity analysis tested the robustness of the results to analytical assumptions. RESULTS: The mean (SD) cost per person was 4540 pounds (4700) in the SCSC group and 4440 pounds (4900) in the ATH group. The mean (SD) QALYs per person for 3 years were 1.67 (0.56) in the SCSC group and 1.60 (0.60) in the ATH group. If decision makers are prepared to pay > or = 2000 pounds to gain 1 QALY, SCSC is likely to be cost effective in 60-90% of cases. CONCLUSIONS: The primary economic analysis and sensitivity analyses indicate that SCSC is likely to be more cost effective than ATH in 60-90% of cases. This result seems to be robust to assumptions required by the analysis. This study is one of a limited number of randomised controlled trials to collect detailed resource use and health status data and estimate the costs and QALYs of treatment for established RA. This trial is one of the largest RA studies to use the EuroQol.

The relationship between social deprivation, disease outcome measures, and response to treatment in patients with stable, long-standing rheumatoid arthritis.

OBJECTIVE: Patients with rheumatoid arthritis (RA) with lower socioeconomic status (SES) are known to have more severe disease, more comorbidity, and higher mortality. It is not known whether SES influences response to treatment in RA. We examined the relationship between area of residence (as a surrogate for SES) and baseline outcome measures and response to treatment, using data from the British Rheumatoid Outcome Study Group randomized controlled trial of aggressive versus symptomatic treatment of long-standing, stable RA. METHODS: A total of 466 patients from 5 centers were recruited to the trial. Baseline data included age, sex, smoking status, and comorbidity. Patients were assigned a Townsend score (a measure of social deprivation) according to their area of residence. Outcome measures including the Disease Activity Score (DAS28), Health Assessment Questionnaire, Medical Outcomes Study Short Form-36, and EuroQol (EQ5D) were recorded at the beginning and end of the 3 year trial. The baseline, 3 year values, and change data were examined by Townsend quintile adjusting for each treatment arm. RESULTS: Significant relationships between increasing social deprivation by area of residence and higher disease activity, higher pain, poorer physical function, poorer emotional aspects of mental health, and lower quality of life were found at baseline (adjusted for age, sex, disease duration, current smoking, treatment center, and treatment group). During the 3 year trial period, patients from the most deprived areas showed greater improvement, with statistically significant greater improvement on DAS28 (p = 0.041) and 28 tender joint count (p = 0.015). CONCLUSION: Area of residence is related to the severity of RA at recruitment and is a predictor of response in a clinical trial situation. The results suggest that measures of SES should be recorded for patients enrolled in clinical trials, longitudinal observational studies, and in the clinical setting.