WHEN AND FOR WHOM ARE BIOLOGICS COST-EFFECTIVE IN RHEUMATOID ARTHRITIS?

  

Purpose: To determine the cost-effectiveness of biologics for rheumatoid arthritis (RA) by age and disability level as measured by the Health Assessment Questionnaire-Disability Index (HAQ).    

Method:   We developed a finite-horizon discrete-time Markov decision processes (MDP) model to identify decision sequences that maximize the net health benefit for hypothetical RA patients, defined by age and HAQ quintile.  We assumed six month cycles and a lifetime horizon.  We modeled transitions among a set of mutually exclusive and collectively exhaustive health states defined by levels of disability as measured by HAQ quintiles.  Higher quintiles of HAQ indicate more disability.  Transition probabilities for biologics and nonbiologics were estimated from the National Data Bank for Rheumatic Diseases.  Direct and indirect costs (as productivity losses) were estimated from the literature.  We calculated an average quality of life weight using the EQ5D instrument for each HAQ quintile.  Both costs and benefits were discounted 3% annually.    

Result:   For a willingness to pay threshold (WTP) of $100,000/QALY, biologics could be cost effective for mildly disabled elderly patients if their cost was reduced by 60%.  The figure illustrates the cost-effectiveness of biologics versus nonbiologics by patient age, HAQ quintile, and WTP, assuming a reduced biologics cost.  As shown in the figure, when the WTP is further increased up to $300,000/QALY, biologics become cost-effective for younger and more disabled patients.  In a sensitivity analysis, we restricted our analysis to newly diagnosed patients (<2 years) and found that biologics were more cost-effective for the more disabled patients.   

Conclusion:   We adopted a novel approach to model the use of biologics in RA as a sequential decision problem.