The LUNDEX, a new index of drug efficacy in clinical practice: results of a five-year observational study of treatment with infliximab and etanercept among rheumatoid arthritis patients in southern Sweden.
OBJECTIVE: To describe the use of the LUNDEX, a new index for comparing the long-term efficacy and tolerability of biologic therapies in rheumatoid arthritis (RA) patients treated in clinical practice. METHODS: Patients (n = 949) with active RA that had not responded to at least 2 disease-modifying antirheumatic drugs (DMARDs) including methotrexate, in whom biologic therapy was being initiated, were included in a structured clinical followup protocol. The protocol included collection of data on diagnosis, disease duration, previous and ongoing DMARD treatment, and dates on which biologic treatment was started and terminated. In addition, data on efficacy measures used for calculating validated response criteria, i.e., the European League Against Rheumatism and American College of Rheumatology response criteria, were collected at fixed time points. Data were prospectively registered from March 1999 through January 2004. The LUNDEX, a new index combining the proportion of patients fulfilling a selected response criteria set with the proportion of patients adhering to a particular therapy, was designed to compare the efficacy of the different therapies. RESULTS: Etanercept had higher overall LUNDEX values compared with infliximab, mostly because of a lower rate of adherence to therapy with infliximab. The relationship between the drugs was consistent irrespective of the response criteria used. CONCLUSION: The LUNDEX is a valuable tool for evaluating drug efficacy in observational studies. It has the advantage of integrating clinical response as well as adherence to therapy in a composite value. Moreover, the LUNDEX has a practical and potentially universal application independent of diagnosis and response criteria.