In England and Wales, rheumatoid arthritis (RA) affects approximately 400,000 people, or 0.5-1% of the population. Those figures come from the "Final Appraisal Determination: Adalimumab, Etanercept, and Infliximab for the Treatment of Rheumatoid Arthritis," published in November last year, by the National Institute for Health and Clinical Excellence (NICE), which describes itself as "the independent organisation responsible for providing national guidance on the promotion of good health and the prevention and treatment of ill health" in the United Kingdom. This document adds, "Of these, approximately 15% have severe disease. RA affects three times as many women as men and has a peak age of onset of 40-70 years."

Many scientists and physicians hope that a growing generation of new drugs could reduce the consequences of RA. The question is: Do these drugs prove cost-effective? Some countries are trying to find out. In 1995, for example, Sweden set up its first register for RA patients, and it collects data on incidence, treatment, symptoms, and so on. So far, there are 89,000 patients in the registry. Then, in 1999, the country's rheumatology society established a second registry specifically aimed at monitoring the safety of new tumor necrosis factor (TNF)-antagonists such as infliximab. "These drugs are just the beginning of a large series coming in from the development pipelines that are able to do fantastic things for patients," says Lars Klareskog of the rheumatology unit at Sweden's Karolinska Institute. "But societies obviously cannot afford for these drugs to be used in a random manner," he adds.

The challenge, Klareskog says, is determining how to best assess the cost-effectiveness of these drugs. One method would make use of data from national patient registries to monitor the drugs, such as the registries with which Klareskog is involved. Because the registries were initially set up to monitor safety, rheumatologists in Sweden are only now starting to bring together the data on cost-effectiveness, Klareskog says. "We don't yet have any ready-made data," he adds. Indeed, a new Swedish study group on health economics was only recently set up in late 2006 to carry out that task.

Still, others have followed the Swedish model across Europe. Similar data are being gathered on autoimmune diseases in countries such as Spain and Germany, notes Gisela Kobelt, founder of European Health Economics, a private company. But teasing out valuable data is difficult, she says, particularly as it is hard to establish good control groups for the registry participants. "For a variety of reasons, patients on therapy are not the same as those who are not on therapy," she says. "That puts us in a difficult situation proving anything in black and white. It's a long way from the [ideal of a] randomized clinical trial."