Diagnosis

The diagnosis of rheumatoid arthritis results from The American College of Rheumatology (ACR) established criteria for the diagnosis of rheumatoid arthritis (R. A.) in 1987.

Chronic polyarthritis (cP) is considered to be present when a patient meets at least four of the seven criteria, with criteria 1-4 having been present for at least six weeks.ACR criteria for the diagnosis of rheumatoid arthritis:

Symptoms
Physical examination
Laboratory values and X-ray image.
Morning stiffness of at least one hour duration
At least three joint areas must simultaneously show soft tissue swelling or joint effusion
At least one joint swelling affects a hand joint, a metacarpophalangeal joint or a metacarpophalangeal joint
Symmetrical simultaneous infestation of the same joint regions on both sides of the body
Rheumatism – knots over bony protrusions or near joints
Suction. Rheumatism – factor (RF) in the blood detectable
Radiological changes typical of rheumatoid arthritis (RA) on an X-ray of the hand

In 2010, on a joint initiative of ACR (American College of Rheumatology) and EULAR (European League against rheumatism), new criteria were established, which offer the possibility of a very early diagnosis as the most important advantage. In contrast to the old criteria from 1987, the new criteria do not include the characteristics of morning stiffness, symmetry of joint involvement and rheumatic nodules.

The presence of erosions in the x-ray image is considered from the outset to be a feature of a reliable diagnosis. A joint infestation is not only a swelling of the joint, but also a painfulness of the joint under pressure. ACR-EULAR classification criteria for R. A. : Joint involvement serology (RF + ACPA) Duration of synovitis Acute phase proteins (CRP/BSG) When 6 points are reached, an R. A. is present.

Prerequisites: confirmed synovitis in at least one joint, exclusion of other diagnoses that explain the synovitis, no typical erosions in the X-ray image (then the R. A. is considered confirmed).

1middle/large joint: 0 points
>1 medium/large joint, not symmetrical: 1 point
>1 medium/large joint, symmetrical: 1 point
1-3 small joints: 2 points
4-10 small joints: 3 points
>10 joints, including small joints: 5 points
Neither RF nor ACPA positive: 0 points
At least 1 test weakly positive: 2 points
At least 1 test strongly positive: 3 points
<6 weeks: 0 points
>6 weeks: 1 point
Neither CRP value nor BSG increased: 0 points
CRP or BSG increased: 1 point

Laboratory diagnostics is used to find a diagnosis, but also to assess the progression/activity of the disease, the response to therapy and it has a prognostic value. The laboratory values should always be assessed in conjunction with other findings.

The rheumatoid factor (RF) or antibodies against citrullinated cyclic peptides (CCP antibodies or ACPA: anti-citrullinated protein antibodies) are available for diagnostic purposes. The rheumatoid factor is detected in the blood. It develops during the first years of the disease.

It is an immunoglobulin that is formed in the joint mucosa of the diseased joints. The rheumatoid factor becomes positive in 75-80% of patients with rheumatoid arthritis primary chronic polyarthritis during the course of the disease. However, it can sometimes also be detected in other diseases and in older age.

CCP antibodies/ACPA are more suitable for early diagnosis, as they can be detected in very early phases of the disease. The combination with a positive rheumatoid factor increases the probability of suffering from rheumatoid arthritis to almost 100%. Prognostically, ACPA appear to be of considerable importance.

High ACPA titers increase the risk for a severe course of the disease. Other typical laboratory findings in the blood of patients with primary chronic polyarthritis are elevated inflammation levels, e.g. CRP (C – reactive protein), and an accelerated blood sedimentation rate (BSG). The iron value as well as hemoglobin (Hb) and leukocytes (=white blood cells) are often lowered, the copper value, gamma globulins and thrombocytes (=blood platelets) may be elevated. Furthermore, laboratory diagnostics serves to exclude other diseases.