Determination method Immunoassay (2nd generation of ACCP tests).

Material under study Blood serum

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Marker of rheumatoid arthritis. See also tests - , .

ACCP belong to anticitrullinated antibodies. The description of citrulline-containing autoantigens characteristic of rheumatoid arthritis has become one of the most important discoveries of rheumatology in recent times in the field of serological diagnosis. Citrulline is not a standard amino acid included in proteins during their synthesis; it is formed as a result of subsequent modification of arginine. The process of citrullination is observed during natural physiological and pathological processes and plays a role in the processes of cell differentiation and apoptosis. Citrullinated antigens were discovered during the search for antigenic targets of antikeratin antibodies - a specific marker of rheumatoid arthritis, detected by immunofluorescence on tissue preparations (see test). It has been shown that antikeratin antibodies recognize only citrullinated forms of the filaggrin protein, which is part of keratin. Among the possible inducers of the formation of antibodies to citrullinated peptides in the mechanism of development of rheumatoid arthritis, citrullinated fibrin, which accumulates in large quantities in the inflamed synovium, is considered. Citrullinated antigens of synovial tissues include citrullinated vimentin. During the development of methods for determining antibodies to citrullinated antigens, it was shown that the use of synthetic cyclic forms of citrullinated peptides provides greater test sensitivity compared to the use of linear peptides. Antibodies to cyclic citrullinated peptide are currently recognized as an informative serological marker of rheumatoid arthritis. Rheumatoid arthritis is a common systemic autoimmune disease that affects about 0.5 - 1% of the population. This disease causes progressive destruction and deformation of joints and may have extra-articular manifestations. Early diagnosis and appropriate treatment of rheumatoid arthritis are critical to disease outcomes. Using a cutoff value of serum ACCP = 5 U/mL, the clinical sensitivity of the test (assessed by the rate of false negative results in the group of patients with rheumatoid arthritis) was 70.6%. The clinical specificity of the test (assessed by the frequency of false positive results) was 99.5% in the group of healthy people and 97.3% in the group of patients with diseases other than rheumatoid arthritis (ankylosing spondylitis, autoimmune thyroiditis, Crohn's disease, dermatomyositis, infection Epstein-Barr virus, Lyme disease, osteoarthritis, polymyalgia rheumatica, polymyositis, psoriatic arthritis, reactive arthritis, scleroderma, Sjogren's syndrome, SLE, ulcerative colitis). Compared to a marker such as IgM-RF (rheumatoid factor), which is not highly specific and can be detected in other rheumatic diseases, infectious diseases and even in 4 - 5% of healthy people, ACCP exhibits significantly higher specificity, positive predictive value and diagnostic accuracy, with similar clinical sensitivity. ACCP can be found in 30% of cases of seronegative rheumatoid arthritis (rheumatoid factor negative). The feasibility of using this test in the early diagnosis of arthritis and for the purpose of prognosis of recently developed rheumatoid arthritis has been demonstrated (ACCP is more associated with progression and erosive arthritis than rheumatoid factor). The use of ACCP for monitoring the activity of the process is not recommended (no correlation with activity markers, including ESR, CRP, has been identified). The test results should be assessed in conjunction with anamnesis and clinical observations, including instrumental examination data.

Antibodies to cyclic citrullinated (citrullinated) peptide or ACDC– the earliest and most specific marker.

Synonyms: ACCP, anti-CCP-AT, anti-CCP, anti-CCP, citrullinated peptide IgG, CCP, anti-cyclic citrullinated peptide antibody IgG, CCP IgG, anti-CCP

Antibodies to cyclic citrullinated peptide are

a group of antibodies (mainly IgG) against the amino acid citrulline, which appears in the composition of joint proteins in rheumatoid arthritis.

ACCP antibodies are highly specific for diagnosing the early stages of rheumatoid arthritis, when correct diagnosis is most important.

Appearance mechanism

for local inflammation in the joint caused by rheumatoid arthritis, the amino acid arginine (under the influence of the enzyme peptidyl agninine deiminase ( peptidyl arginine deiminase, PAD) is converted from dead leukocytes to citrulline
Normally, there is no citrulline in joint proteins, and antigen-presenting cells (macrophages, dendritic cells, B-

Antigen presenting cells and – a group of cells that, after absorbing an antigen (an unknown particle), present it on their surface for recognition by T lymphocytes.

the antigen-presenting cell exposes citrulline as an “aggressor”, a “stranger” that needs to be destroyed, to which T-lymphocytes react
active division of T-lymphocytes is triggered against cells containing citrulline and B-lymphocytes - producing antibodies against citrulline - anti-CCP

Features of the analysis

The study has low sensitivity (40-50%) - a negative test result for ACCP does not allow exclusion. At the same time, high specificity (95-99%) - a positive test result for ACCP indicates an extremely high probability of a diagnosis of rheumatoid arthritis.

The ACCP values are stable, even with successful treatment, so if a diagnosis of rheumatoid arthritis is made, the test should not be repeated.

In the new classification criteria for rheumatoid arthritis (published in 2010 by the American Rheumatological Association), analysis of ACCP together with (RF) serves as a criterion for the diagnosis of rheumatoid arthritis.

Rheumatoid arthritis

Rheumatoid arthritis is the most common autoimmune disease in the world. The reason is unknown. It is assumed that the combination of burdened heredity and the action of external factors triggers autoimmune mechanisms (read above). This means that the immune system no longer correctly recognizes the cells of its own body and mistakes them for foreign ones. Antibodies are formed that destroy the joint - the synovial membrane, cartilage.

is a chronic inflammation of the membranes of several joints, destruction of their cartilaginous lining and adjacent bone. The result of rheumatoid arthritis is complete destruction of the joint and disability.

Symptoms

symmetrical pain, swelling, sensitivity, redness of the joints of the hand - painlessness at rest, pain appears on palpation or movement
morning stiffness (more than 30 minutes) is a characteristic symptom of rheumatoid arthritis
subcutaneous hard formations - rheumatic nodules
joint pain due to weather changes
increased fatigue for no apparent reason
increase in body temperature in the absence of an obvious cold or acute respiratory infection
weight loss

Advantages

Antibodies to citrulline peptide appear in the blood 3-6 months (sometimes 1-2 years!) before the first symptoms, which makes it possible to diagnose the disease in the early stages, when treatment is most effective
ACCPs are associated with a more aggressive and unfavorable course of rheumatoid arthritis, making early diagnosis and more aggressive treatment even more urgent
ACCP analysis helps to exclude arthritis associated with - rheumatoid factor in viral hepatitis C is increased, which makes it impossible to use it for diagnosis

Comparison of ACCP and rheumatoid factor

	Rheumatoid factor	Meaning
		maximum likelihood of rheumatoid arthritis, often more severe
		if there are symptoms of rheumatoid arthritis, then a diagnosis of an early form of rheumatoid arthritis is made; if not, there is a high probability of the disease in the future, repeated tests are needed
		evaluate symptoms more carefully, exclude other inflammatory or autoimmune pathologies
		the diagnosis of rheumatoid arthritis is unlikely, but it should be remembered that rheumatoid arthritis is a clinical diagnosis and can be made if the antibody test is negative

Indications

symptoms of arthritis and early joint stiffness - for early diagnosis of rheumatoid arthritis
predicting the severity of rheumatoid arthritis
with a negative result of the rheumatoid factor test, but joint symptoms
differential diagnosis of other joint diseases
in a complex of rheumatoid tests

Norm, U/l

negative result – less than 20
weakly positive result - 20.0-39.9
positive - 40-59.9
strongly positive – more than 60

For all age groups.

Remember that each laboratory, or rather laboratory equipment and reagents, has its own standards. In the laboratory test form they appear in the column - reference values or norm. Analysis for ACCP must be carried out in the same laboratory.

Determination method Immunoassay (2nd generation of ACCP tests).

Material under study Blood serum

Home visit available

Marker of rheumatoid arthritis. See also tests - , .

Code on the form: 26.35.

CCP antibodies (Antibodies to cyclic citrulline-containing peptide) (count)

Name in Latin

Ibi elementorum ad cyclic citrulline continens peptide

Name in English

Antibodies to cyclic citrulline peptide-containing

Study Information

Rheumatoid arthritis (RA)- the most common autoimmune disease. This disease is characterized by inflammation of the synovium, which spreads symmetrically from small to large joints. Initial symptoms of the disease include painful swelling of the joints of the fingers with loss of joint flexibility in the morning. Early diagnosis and prompt initiation of appropriate therapy are essential to keep the disease under control.

Rheumatoid arthritis (RA) is a new, highly specific marker of rheumatoid arthritis. Detection of the disease in the early stages.

Until recently, the most widely used serological test for suspected RA was rheumatoid factor (RF). These are antibodies (mainly IgM class) that react with gammaglobulins and are found in 60-80% of patients with RA. RFs are sensitive but not very specific markers of RA, since they are also found in healthy people, in patients with infectious diseases or in other autoimmune diseases (systemic lupus erythematosus, Sjogren's syndrome, scleroderma, etc.).

It has now been proven that new And highly specific RA marker are antibodies to cyclic citrulline-containing peptide (CCP). Antibodies to cyclic citrulline-containing peptide are autoantibodies that interact with synthetic peptides containing the atypical amino acid citrulline.

Antibodies to CCP are predominantly of the IgG class, and their specificity for RA is about 97%. They are detected at very early stages of the disease. Patients with antibodies to CCP develop more severe joint damage. Antibodies to CCP have higher specificity compared to RF (anti-CCP - 97%, RF - 63%). This analysis is performed on a closed automatic analyzer Cobas 6000 (Roche, Switzerland).

Antibodies to citrullinated vimentin (anti-MCV);
C-reactive protein.

Indications for the purpose of the study

1. Early diagnosis of rheumatoid arthritis;
2. Diagnosis of seronegative (for rheumatoid factor) forms of rheumatoid arthritis;
3. For prognostic purposes, with recently developed rheumatoid arthritis.

Preparing for the study

It is recommended to donate blood in the morning, between 8 and 11 a.m., on an empty stomach (at least 8 hours must pass between the last meal and blood collection, you can drink water as usual), and on the eve of the test, have a light dinner with limited intake of fatty foods.
1-2 hours before donating blood, refrain from smoking, do not drink juice, tea, coffee, you can drink still water. Avoid physical stress (running, quickly climbing stairs), emotional excitement. It is recommended to rest and calm down 15 minutes before donating blood. The study is recommended to be carried out before starting immunosuppressive therapy.