The score estimates the probability of a patient with rheumatoid arthritis to suffer from a serious infection during the next 12 months, based on data from other patients with similar risk profiles. It shows that risks resulting from higher age, poor functional status, co-morbidity and treatment have to be balanced against each other. There may be risk factors for individual patients that are not included in the score, e.g. diabetes mellitus, which was not significant in our model but may play a role in individual patients. The score therefore cannot replace the physician’s careful risk assessment and judgement.

This instrument was developed with data from 5,044 patients with rheumatoid arthritis observed in the German Biologics Register RABBIT (Strangfeld A et al. Ann Rheum Dis. 2011;70(11):1914-20) and replicated in 2,990 patients. High agreement between development and replication was shown. However, we do not know how this score performs in other populations and under other health care systems.

In order to enable usage of the score also for biologic agents with different modes of action than TNF-a inhibitors, it was extended in 2013 based upon data from 2,612 patients. For the more recent substances it has not yet been replicated; the results are therefore preliminary (Zink A et al. Ann Rheum Dis. 2013 Jun 28).