This DAS28 CRP for rheumatoid arthritis calculator evaluates the RA disease activity with the help of c-reactive protein and the number of swollen, tender joints. There is more information on the model formula and the result interpretation below the form.
How does this DAS28 CRP for rheumatoid arthritis calculator work?
This health tool helps in the routine assessment of rheumatoid arthritis disease activity with CRP (C-reactive protein) laboratory values, joint evaluation and a subjective opinion on general health.
The DAS28-CRP is a modified and simplified version of the original DAS for rheumatoid arthritis assessment, which eliminates some of the variables and replaces the erythrocyte sedimentation rate (ESR) with the C-reactive protein (CRP).
The formula used by the DAS28 CRP for rheumatoid arthritis calculator is the following:
DAS28-CRP = 0.56 x sqrt(TJc) + 0.28 x sqrt (SJc) + 0.36 x ln(CRP + 1) + 0.014 x GH + 0.96
■ TJc = number of tender joints;
■ SJc = number of swollen joints;
■ CRP = c-reactive protein laboratory value as a blood marker of inflammation;
■ GH = global health assessment which represents a subjective assignation of points on a scale from 0 to 100 where 0 means very good and 100 means very bad. In practice, a 10 cm rule is used and the physician awards a number of mm which are then used in the score.
The 28 joints used in the score are:
■ Proximal interphalangeal (10);
■ Metacarpophalangeal (10);
■ Wrists (2);
■ Elbows (2);
■ Shoulders (2);
■ Knees (2).
The original score was created to support with the standardization and comparison of results in clinical trials involving rheumatoid arthritis treatments but due to the good monitoring characteristics, was introduced in routine practice.
DAS28-CRP score interpretation
In most cases, DAS-CRP values range between 2.0 and 10.0, the higher the score, the higher the disease severity. A cut off score of 2.6 sets the difference between low activity arthritis and remission.
Scores using patient performed joint count, such as the DAS models have shown high reliability and are actively used as an alternative to other physician derived scores in monitoring RA.
The following table interprets the possible DAS28-CRP scores:
|Present DAS28-CRP||Interpretation||Decrease > 1.2||Decrease > 0.6 but ≤ 1.2||Decrease ≤ 0.6|
|< 2.6||Remission||good improvement||moderate improvement||no improvement|
|≥ 2.6 but ≤ 3.2||Low||good improvement||moderate improvement||no improvement|
|> 3.2 but ≤ 5.1||Moderate||moderate improvement||moderate improvement||no improvement|
|> 5.1||Active||moderate improvement||no improvement||no improvement|
Rheumatoid arthritis guidelines
This is a progressive autoimmune disease of the joints which results in immobility and deformities in the joints of the fingers, wrists and knees.
There are three main types of arthritis:
■ Osteoarthritis – “wear and tear” of the joints from old age, injury or caused by obesity.
■ Rheumatoid arthritis – the autoimmune condition.
■ Psoriatic arthritis – joint condition associated with the psoriasis skin disease.
Symptoms of rheumatoid arthritis include pain and swelling, stiffness of the joints, general tiredness, rheumatoid nodules (1 in every 5 people diagnosed with RA).
Diagnosis is usually put through blood tests as CRP and ESR to evidence inflammation, x-rays to evidence damage to the joints and MRI scans in early diagnosis.
1) Heegaard C, Dreyer L, Egsmose C, Madsen OR. (2013) Test-retest reliability of the disease activity score 28 CRP (DAS28-CRP), the simplified disease activity index (SDAI) and the clinical disease activity index (CDAI) in rheumatoid arthritis when based on patient self-assessment of tender and swollen joints. Clin Rheumatol; 32(10):1493-500.
2) 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.
3) 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.
4) Inoue E, Yamanaka H, Hara M, Tomatsu T, Kamatani N. (2007) Comparison of Disease Activity Score (DAS)28‐ erythrocyte sedimentation rate and DAS28‐ C‐reactive protein threshold values. Ann Rheum Dis; 66(3): 407–409.15 Feb, 2016