There are several versions of DAS, but they all measure disease burden using patient global health (patient self-assessment), tender joint-counts and swollen joint-counts (up to 28), and the ESR (erythrocyte sedimentation rate) or CRP (C-reactive protein). The DAS can be calculated using a specific program or calculator -- or by going to a website, http://www.das-score.nl/. If you have an iPhone or other smart phone, there are DAS apps available.
History of DAS
The beginning of DAS is considered circa 1983. The original DAS included the Ritchie articular index, the 44 swollen-joint count, the ESR (erythrocyte sedimentation rate) and a general health assessment on a visual analogue scale.
Usefulness in Clinical Practice
Decisions about treatment can be based on current DAS28 values or on changes in DAS28 values compared to values before treatment started. The DAS28 high and low disease activity thresholds have been validated. There also is a clearly defined relationship between the mean DAS during a certain period and the amount of x-ray damage that a patient develops within that time period.
Scoring of DAS28
After the complex calculation has been made:
DAS28 >5.1 = high disease activity
DAS28 <3.2 = low disease activity
DAS28 <2.6 = remission
Other versions of DAS28 exist that allow CRP to be used instead of ESR -- or that allow omission of either CRP or ESR. Check out the DAS calculator options.
Sources:
Disease Activity Score. Rheumatoid Arthritis: Early Diagnosis and Treatment. Cush, Weinblatt, and Kavanaugh. Third Edition. Published by Professional Communications, Inc. (2010).
The DAS28 Score. National Rheumatoid Arthritis Society. 11/7/2007.
http://www.nras.org.uk/about_rheumatoid_arthritis/established_disease/managing_well/the_das28_score.aspx
