This DAS28 ESR for rheumatoid arthritis calculator determines the RA disease activity score based on the erythrocyte segmentation rate. You can find out more about the score and its interpretation in the text below the form.
How does this DAS28 ESR for rheumatoid arthritis calculator work?
This health tool is used in the monitoring of rheumatoid arthritis activity because it accounts for erythrocyte sedimentation rate which is a marker of inflammation.
This Disease Activity Score is based on the original DAS28 and presents a simplified version which covers 4 variables:
■ TJc = number of tender joints;
■ SJc = number of swollen joints;
■ ESR = Erythrocyte sedimentation rate laboratory value;
■ GH = global health assessment which is based on the patient assigning an imaginary value to the perceived level of health, between very good and very bad, usually on a 10 cm ruler. The assessor will then measure and assign a number of mm in order to perform the calculation further.
The formula used in the DAS28 ESR for 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 scores are deemed to be of similar specificity and sensitivity and are currently used in clinical practice.
DAS28-ESR score interpretation
The following table presents the disease activity interpretation based on the results received after the DAS28-ESR is computed:
| Present DAS28-ESR | Interpretation |
| < 2.6 | Remission |
| ≥ 2.6 but ≤ 3.2 | Low |
| > 3.2 but ≤ 5.1 | Moderate |
| > 5.1 | Active |
The cut off point for remission has been established at 2.6, however, the guidelines note that even patients with 2.6 might continue to present at least 2 swollen joints. In some cases, the number of swollen, tender joints might be even higher, but due to the other variables in the DAS28-ESR, the composite index to indicate remission.
The two different versions of DAS28, the CRP and ESR, not only vary due to the parameter used but also in classifying the severity of RA. Although at first hand, the thresholds for disease activity are similar, ESR results are mostly oriented towards the high zone of results, especially in female subjects.
References
1) Wells G, Becker J-C, Teng J et al. (2009) Validation of the 28-joint Disease Activity Score (DAS28) and European League Against Rheumatism response criteria based on C-reactive protein against disease progression in patients with rheumatoid arthritis, and comparison with the DAS28 based on erythrocyte sedimentation rate. Ann Rheum Dis; 68(6): 954–960.
2) 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
3) Sengul I, Akcay-Yalbuzdag S, Ince B, Goksel-Karatepe A, Kaya T. (2015) Comparison of the DAS28-CRP and DAS28-ESR in patients with rheumatoid arthritis. Int J Rheum Dis; 18(6):640-5.
4) Anderson J, Caplan L, Yazdany J et al. (2012) Rheumatoid Arthritis Disease Activity Measures: American College of Rheumatology Recommendations for Use in Clinical Practice. Arthritis Care Res (Hoboken); 64(5): 640–647.
15 Feb, 2016