A Norwegian DMARD register: prescriptions of DMARDs and biological agents to patients with inflammatory rheumatic diseases.

Information concerning the effectiveness of drug therapy cannot be obtained only from randomized controlled clinical trials, due to limitations such as a short time frame and narrow inclusion and exclusion criteria. Therefore, complementary longitudinal observational studies performed in a real life setting are required. NOR-DMARD, a Norwegian 5-center register, was established in December 2000. All DMARD prescriptions to patients with inflammatory arthropathies are included, and patients are followed longitudinally with a variety of assessments. As of 2005, 4683 DMARD regimens have been included. Methotrexate is the most commonly used DMARD in rheumatoid arthritis and psoriatic arthritis. The proportions of patients who have received anti-TNF drugs in rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, juvenile arthritis and other diseases have been 22.5, 21.6, 53.8, 36.9 and 9.7%, respectively. The proportion of patients receiving anti-TNF drugs is considerably higher in 2004 than earlier, and criteria for prescribing anti-TNF drugs appear to be trending toward patients with less severe and active disease. Confounding by indication or channeling bias represents a challenge for the group comparisons of longitudinal effectiveness data, but can be addressed by modern statistical techniques. The NOR-DMARD register may in the future provide comparative real life effectiveness data that may also be used in cost-effectiveness analyses.