The DAS28 score

Dr Patrick Kiely, Consultant Rheumatologist , St George’s Hospital, Tooting
Original article: 11/07/2007
Reviewed: 28/03/2011
Next review due: 28/03/2014

The DAS28 is a measure of disease activity in rheumatoid arthritis (RA). DAS stands for 'disease activity score' and the number 28 refers to the 28 joints (commonly affected by RA) that are examined in the assessment. An assessment of DAS involves the rheumatologist or specialist nurse looking at the number of tender and swollen joints (out of the 28), the erythrocyte sedimentation rate (ESR) or C reactive protein (CRP) both of which measure the degree of inflammation in the blood, and the patient’s ‘global assessment of health' (indicated by marking a 10 cm line between very good and very bad). These results are then fed into a complex mathematical formula to produce the overall disease activity score. A DAS28 of greater than 5.1 implies active disease, less than 3.2 well controlled disease, and less than 2.6 remission.

Your doctor or nurse practitioner will routinely make an assessment of how active your RA is, each time they see you. There is no ‘best’ measure of this, but there are various measurements that can be used. These include:

• examination of your joints (usually more than the 28 that make up the DAS28 score).
• global scores of pain and overall status.
• blood markers of inflammation (eg ESR and CRP). For more information please see our article on blood tests: Laboratory tests used in the diagnosis and monitoring of RA. 
• questionnaires (eg the HAQ (Health Assessment Questionnaire) which assesses function).
• x-rays and newer imaging techniques such as ultrasound and MRI.

The DAS28 is a composite score derived from 4 of these measures. This ‘28’ version is a simplification of the original DAS score, which requires 44 joints to be counted. Further versions of the DAS28 allow the CRP to be used instead of the ESR, or the omission of either.

The HAQ questionnaire assesses function

The DAS score was originally developed by Dutch rheumatologists for the purpose of standardizing and comparing results in clinical trials of new drugs for treating RA. With time the DAS28 has also been applied to routine clinical practice. In the UK a score equal to or greater than 5.1 on two occasions is one of the mandatory criteria required to be eligible for NHS funded treatment with anti-TNF therapies. You will therefore have had at least two DAS28 scores if you are receiving this treatment.

Whilst it is appealing to be able to calculate a number on a measured scale to indicate how active or well controlled your RA is; the DAS28 score has not been adopted in day-to-day (non anti-TNF) practice by all rheumatologists in the UK. This is in part because there are some pitfalls in the interpretation of the score. For example if you never have a very high ESR blood result (even during a flare), or if your RA particularly affects the feet (these are not included in the 28 joint count) the score may be misleadingly low. Alternatively if you always have many tender joints when all other markers of inflammation and RA disease activity are quiet the score may be misleadingly high. It can also be difficult to decide whether an individual joint is swollen or tender, and this uncertainty may lead to misleading variability in the score, when assessed by the same person on different occasions and also when assessed by several people on one occasion.

Nevertheless if your rheumatology department does measure the DAS28 routinely, then you might find that this is one of the reasons why a change in treatment is being suggested. This can apply to both an increase or a decrease in therapy in the light of a high or low score respectively. A persistently high score has been found to increase the likelihood of progressive joint damage, even in patients who appear to be doing well. Therefore, although not a perfect measure of disease activity, it might be useful to ask ‘What’s my DAS28?’ next time you visit the rheumatology department.

For more information on DAS and to view the NRAS video on DAS, please click here

References available on request

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