The DAS28 is the main outcome measure used to assess disease activity in Rheumatoid arthritis. It is in routine use in most Rheumatology clinics, so it is being used to make treatment decisions for individual patients. The validation of the DAS28 ESR was based on the application of the OMERACT principles and the use of mathematical and statistical analysis of a number of datasets from clinical practice. To find out more about the score please go to www.das-score.nl website. On this web site you can find a standard spreadsheet calculator with all the correct formulas.
Although I use this score on a daily basis to guide my ‘treat to target’ strategy, I am aware that it can have limitations when applied to the individual. For instance, I found that some patients with RA and Fibromyalgia had misleading scores. In these patients the swollen joint and ESR components of the score were relatively low compared to the VAS and tender joint counts. See my blog post on this. These observations have been confirmed in a number of studies, and more recently the important paper by Kristensen et al which confirms the prognostic value of the Swollen to Tender ratio.
Because of this I have developed a spreadsheet tool to highlight how each of the components makes up the score. You can enter any values you want and see how the pie chart changes. The best thing to do is to download the tool and crosscheck the scores with the official spreadsheet tool. Because I have left the spreadsheet unprotected it is possible that someone could have edited it and spoiled the formula. Remember, this is only an educational tool! Please leave a comment if you find it useful or if you think it can be improved.
Kristensen, L. E., Bliddal, H., Christensen, R., Karlsson, J. A., Gülfe, A., Saxne, T. and Geborek, P. (2014), Is Swollen to Tender Joint Count Ratio a New and Useful Clinical Marker for Biologic Drug Response in Rheumatoid Arthritis? Results From a Swedish Cohort. Arthritis Care Res, 66: 173–179.