Cost-effectiveness of risk-stratified blood-test monitoring strategies for adults with inflammatory conditions

Objectives To assess the cost-effectiveness of extending the interval between monitoring blood tests beyond 3-monthly intervals during established treatment of adults prescribed low-dose weekly MTX (≤25 mg/week), LEF or SSZ.

Methods Published prognostic models that estimated the risk of stopping treatment due to abnormal blood test results during 5 years of established treatment were incorporated into a cost-effectiveness model. The consequences of having an extended monitoring period and a delay in stopping treatment was estimated by clinicians as the probability of someone having 1 of the 11 adverse events (AEs) that could be avoided with monitoring. The clinicians erred towards overestimating the risks. The costs and quality-adjusted life year loss of the AEs were sourced from recent National Institute of Health and Care Excellence appraisals or from targeted searches. Incremental net monetary benefit (iNMB) of 6-, 12- and 24-monthly monitoring, compared with three monthly monitoring was calculated for each drug conditional on risk decile.

Results Our analyses show that extending the duration between monitoring appointments is cost-effective in all scenarios, even in a pessimistic analysis, where the risks of all AEs were tripled, and the costs of some AEs were increased. In the base case, biennial monitoring was often most cost-effective although the iNMB between annual and biennial monitoring was often small.

Conclusion Extending the interval between monitoring blood tests appears to be cost-effective with annual monitoring producing consistently good results regardless of assumptions related to risks of AEs, risk decile or treatment.