DAS28 ESR For Rheumatoid Arthritis Calculator

DAS28 ESR explained

This is a disease activity score based on the erythrocyte sedimentation rate (as inflammation marker) and used in the monitoring of rheumatoid arthritis activity.

There are four variables used:

■ Number of tender joints (TJc);

■ Number of swollen joints (SJc);

■ Erythrocyte sedimentation rate laboratory value (ESR);

■ Global health assessment (GH).

In the global health assessment the patient is asked to assign an imaginary position to the perceived level of health, between very good and very bad, on a 100 mm ruler.

The assessor will then measure where the indicated point is on the ruler and assign a numeric value between 0 and 100.

The formula used in the rheumatoid arthritis calculator is the following:

DAS28 ESR = 0.56 x sqrt (TJc) + 0.28 x sqrt (SJc) + 0.70 x ln(ESR) + 0.014 x GH

The 28 joints evaluated in the score are:

■ Proximal interphalangeal (10);

■ Metacarpophalangeal (10);

■ Wrists (2);

■ Elbows (2);

■ Shoulders (2);

■ Knees (2).

There is another method, the DAS28-CRP with the same usage in rheumatoid arthritis monitoring, but using a different blood marker of inflammation, the C-reactive protein.

The two scores, the DAS28 CRP and ESR were found to be of similar specificity and sensitivity. However, the ESR results tend to be higher than the CRP ones, especially in female subjects.

Result interpretation

The score is interpreted compared to a cut-off point of remission, established at 2.6. However, this is not always accurate as patients with this score are likely to continue presenting at least 2 swollen joints.

The table below introduces the possible score intervals and their disease activity interpretation:

DAS28 score also carries the limitation that in some cases, although the number of swollen, tender joints is high, the resultant score may be low (indicating remission) because of the other items in the composite index.

About the study

The DAS28 ESR was created following a prospective study by van der Heijde et al. in which 113 patients with early rheumatoid arthritis were analysed.

Where treatment was initiated with slow acting antirheumatic drugs, high disease activity was established.

Where treatment with slow acting antirheumatic drugs remained unchanged for at least one year, was stopped or not even initiated, low disease activity was established.

Therefore, two patient groups were formed. Factor and discriminant analysis were used to go through a large number of clinical and laboratory variables.

The resultant score consisted of the Ritchie index, swollen joints, erythrocyte sedimentation rate, and general health, ordered in declining importance.

Original source

van der Heijde DM, van 't Hof MA, van Riel PL, Theunisse LA, Lubberts EW, van Leeuwen MA, van Rijswijk MH, van de Putte LB. Judging disease activity in clinical practice in rheumatoid arthritis: first step in the development of a disease activity score. Ann Rheum Dis. 1990; 49(11):916-20.

Validation

Elizabeth M. A. Hensor E.M.A, Emery P. Bigham S et al. Discrepancies in categorizing rheumatoid arthritis patients by DAS-28(ESR) and DAS-28(CRP): can they be reduced? Oxford Journals Medicine & Health Rheumatology; 49(8):1521-1529.

Other references

1. Sengul I, Akcay-Yalbuzdag S, Ince B, Goksel-Karatepe A, Kaya T. Comparison of the DAS28-CRP and DAS28-ESR in patients with rheumatoid arthritis. Int J Rheum Dis. 2015; 18(6):640-5.

2. Anderson J, Caplan L, Yazdany J et al. Rheumatoid Arthritis Disease Activity Measures: American College of Rheumatology Recommendations for Use in Clinical Practice. Arthritis Care Res (Hoboken). 2012; 64(5): 640–647.