Markers of autoimmune diseases are antibodies to cyclic citrulline. ACC blood test

Antibodies to cyclic citrullinated peptide, and if maximum accuracy is maintained, such a study, by definition, represents the most effective method identifying a person with such a dangerous disease as arthritis, which develops in the rheumatoid form. Antibodies of this type begin their formation in the human body long before such a pathology begins to manifest itself. various symptoms, it happens that it’s a year and a half. It must also be said that it is very difficult to determine such antibodies by other methods; often this becomes possible only as the disease progresses, but its treatment in such cases becomes significantly more difficult.

Why is this kind of testing carried out and how is this procedure carried out? The main goal of such a study is to identify the degree of articular damage, and also through the ACCP test it is possible to assess deformative tissue development. Such a research method is necessary so that the occurrence of such a dangerous and common disease as arthritis can be determined in a timely manner. Thus, it is possible to prescribe the most effective treatment method, this is very important, since such an illness should be treated exclusively according to an individual approach.

It should be noted that citrulline is a substance that is part of metabolic products in the human body. The substance is produced from amino acids when various kinds of biochemical reactions begin to actively influence them.

If the person’s condition is sufficiently satisfactory, citrulline can be removed from the human body quite quickly and without much difficulty. The fact is that it has nothing to do with the formation of protein-type associations. But when a person begins to develop rheumatoid arthritis, the normal composition of the blood begins to change significantly, and it is this phenomenon that can be detected during analysis. The peptide that contains the metabolic product becomes such that the human body considers it a foreign object, so that active production of antibodies begins. This process begins to form in the process of clear and organized work of the immune system, which protects the human body from the negative effects of various harmful substances.

As for ACCP, to put it more simply, this is a group of special antibodies; they have the unique ability to recognize elements of a certain shape in the human body. This should include protein antigens that also have a certain amount of citrulline.

It should be noted that ailments affecting the musculoskeletal system can be very different, but it is arthritis in the rheumatoid form that poses an increased danger. Moreover, it is very common and extremely difficult to treat, especially if it has an advanced form.

If we talk about the features of this pathology, it should be noted that this is an autoimmune disease, which in chronic form. If we talk about how it manifests itself, the following is noted here:

• joints hurt a lot;
• the joint capsule undergoes an inflammatory process;
• joints undergo dystrophic changes

The situation is further aggravated by the fact that quite often doctors, in addition to arthritis, reveal the presence of other pathologies, and they no longer have an articular form, but they begin to actively develop precisely under the influence of such a disease. It is important to note that the value of the analysis of antibodies to cyclic citrullinated peptide is very important, because if such a test is carried out on time, then the disease can be caught at the very initial stage of its development, which makes treatment faster and more effective.

How arthritis develops, features of symptoms

The symptoms of such a disease can be very different, but there is one general sign - joints and tissues are affected. When a person is affected by such a disease, the following symptoms are most often observed:

• legs hurt a lot;
• leg tissues swell;
• those places where there is a bone connection begin to turn red;
• it becomes difficult for a person to bend his legs at the knees, then their functionality is generally seriously impaired;
• in the morning a person has a feeling that his joints are stiff.

Modern medicine makes it possible to identify such a dangerous pathology at the earliest stages by undergoing a blood test for ACCP, the result of which can most accurately show the absence or presence of a rheumatoid factor. However, it cannot be said that the results of such an analysis are 100 percent reliable, since they can also appear in other pathologies that have an advanced form.

If a person begins to show signs such as bone or joint deformation, if he is deprived of the ability to move normally, then he is first examined by doctors, after which a similar analysis can be prescribed, since the main diagnostic measure is the most common today.

After the testing process is completed, the doctor begins to find out the signs of the disease, takes into account the amount of antibodies in the blood, and also determines the level of inflammation in the joint tissues. It is very important to understand that the presence of antibodies that appeared in a person’s blood after such an analysis was carried out is the primary and main sign of such an ailment as rheumatoid arthritis.

If the amount of antibodies significantly exceeds the norm, this means that a damaging process is already underway in the human body; joints and bones begin to deform. In such cases, the person must be urgently hospitalized; this is the only way to restore mobility to the musculoskeletal system through a certain amount of time.

How is ADDC analysis carried out?

In order to determine the amount of antibodies as accurately as possible, blood should be taken from a vein. After the collection has been carried out, you need to extract the serum from it; it remains able to be stored for a whole week, but for this a constant, uniform temperature must be ensured.

The test for the amount of antibodies to the containing peptide is carried out as follows:

1. The beam will scatter on the test tube, which contains the material for research.
2. The results must be compared with those indicators that are optimal.

It is noteworthy that the ACCP norm does not differ between men and women; it is the same for everyone: 3 U/ml. If, based on the results of the analysis, it becomes clear that the norm is significantly exceeded, this indicates that the inflammatory process in the human body has already begun, which means it is necessary to take appropriate measures as urgently as possible.

In conclusion, it should be noted that the results of the analysis and the amount of antibodies that are present in the blood are essential for how the pathology can be treated. So, if a person has even the slightest suspicion of the presence of such a pathology, this kind of analysis is necessary. We must understand that the success of treatment, and therefore not only health, but sometimes also a person’s life, largely depends on the timely diagnosis of the disease.

Diagnostics in rheumatology is extremely difficult. Antibodies to cyclic citrullinated peptide released during serological study A blood product from patients with rheumatoid arthritis (RA) is considered the gold standard for diagnosis. Early detection of this severe autoimmune lesion of the musculoskeletal system will help prevent or reduce degenerative changes in it. But the ACCP norm does not always indicate the absence rheumatoid arthritis.

The ratio of antibodies to cyclic citrullinated peptide in serology can make an accurate diagnosis of rheumatoid arthritis.

What it is?

ACCP for rheumatoid arthritis are protein fractions, where the structural elements are amino acids, among which arginine is found - the building block of human genetic material. A derivative of this amino acid is citrulline, which is part of the urea formation cycle. In a healthy person, citrulline does not participate in protein synthesis and is soon eliminated from the body without joining metabolism. The Anti-CCP level in the blood increases if the patient has rheumatoid arthritis. In this case, citrulline is directly involved in the apoptotic processes of cell death in the body.

Why is analysis needed?

If the patient has characteristic complaints during the initial examination and history taking, he is prescribed an X-ray examination. When radiographs show traces of degenerative-dystrophic phenomena in the joints, the diagnosis needs to be confirmed using laboratory tests. Positive analysis on ACCP for rheumatoid arthritis means the need to start specific treatment. General and biochemical analysis blood tests can only confirm the diagnosis, but not refute it.

Advantages of testing Abs to citrulline peptide

Deciphering the level of antibodies on CP indicates the presence in the synovial fluid of the joints of specific immune complexes that provoke the disease. The limits of the indicators indicate the severity of the disease. Their increase indicates rheumatoid arthritis. The acute course of this rheumatological pathology requires immediate initiation of therapy. And since the rapid test is performed quite quickly, and the laboratory assistant does not need specific equipment to collect biomaterial, the diagnosis is obtained in the shortest possible time. The gradation of ACCP concentration allows one to judge whether it is weakly positive or strongly positive result.

Preparation for the event

Material is collected for Anti CCP using venipuncture (venous blood collection). Doctor general practice is obliged to provide the patient with recommendations on special preparation for the test:

• On the day of the visit to the laboratory, the patient must abstain from food and drink. You can only drink a glass of clean water.
• A few days before the analysis, the patient completely excludes fried and fatty foods, alcohol and foods with dyes from the menu.
• The patient should not use dietary supplements and vitamin complexes within a week before the start of laboratory testing.
• It is advisable to exclude any physical exercise, physiotherapeutic procedures that increase the body’s temperature and accelerate metabolic processes.

How is citrullinated peptide tested?

The blood collection procedure takes place in a laboratory where strict sterility is maintained. The skin of the upper third of the inner surface of the forearm is treated twice with a cotton swab soaked in an alcohol solution. A special tourniquet is applied to the shoulder. The patient must make flexion movements with the fingers of the hand - this increases the blood flow in the vessels of the hand. A laboratory assistant, using special vacuum systems, collects biological material. The latter is delivered to the laboratory and analyzed within a few hours. Blood serum can be stored for another seven days at a certain temperature. The study is carried out using an enzyme immunoassay analyzer, then its transcript is provided.

ASSR norm

If the concentration of antibodies to cyclic citrullinated peptide reaches 3 U/ml, this is a negative indicator. This figure is considered the norm for a healthy person. Upper limit normal level antibodies to cyclic citrullinated peptide - up to 5 U/ml. The norm for women is the same as for men. But in pregnant women and children (during the formation of the musculoskeletal system), the indicators can reach 48-49 U/ml, in the elderly - 50. The table shows the antibody concentration value:

It is advisable to confirm the analysis with data on the level of rheumatoid factor (RF), a marker of immunoglobulin nature. There is also a possibility that the patient has seronegative rheumoarthritis, which cannot be determined using this test.

Antibodies to cyclic citrullinated peptide (ACCP, A-CCP)– heterogeneous specific immunoglobulins that interact with antigens of proteins containing citrulline. They are laboratory signs of rheumatoid arthritis. The anti-CCP test is used for early diagnosis of the disease, its differentiation from autoimmune pathologies with articular syndrome, and assessment of the likelihood of joint destruction in persons with a confirmed diagnosis. Venous blood serum is tested by ELISA. The reference value range is 0-5 U/ml, data is prepared within 1 business day.

Citrulline is a metabolic product formed from an amino acid. It is not involved in the production of proteins and is completely eliminated from the body. Rheumatoid arthritis is accompanied by changes in the enzyme composition and an increase in the concentration of arginine deaminase. Under its influence, citrulline is incorporated into peptides. The resulting complexes are foreign to the body, the immune system triggers the production of specific immunoglobulins. Antibodies to cyclic citrullinated peptide are a laboratory sign of early rheumatoid arthritis. The advantage of the ACCP study is its high specificity; the limitation is the lack of correlation between antibody levels and activity pathological processes.

Indications

The A-CCP test is used to diagnose rheumatoid arthritis. Indications:

• Signs of joint damage. On initial stages with fuzzy clinical picture rheumatic diseases and other autoimmune pathologies with articular syndrome manifest themselves similarly. Patients complain of pain and stiffness of the joints, fever, weakness; upon examination, limited mobility, local swelling, redness, and skin rashes are detected. The study is performed for differential diagnosis.
• Hereditary predisposition. Immunological changes in RA develop 1.5-2 years before the appearance of the first symptoms. The test is prescribed to people at risk - those who have close relatives with an established diagnosis. Determination of ACCP allows for early diagnosis of pathology.
• Confirmed diagnosis of RA. Anti-CCP are detected in rapidly progressing forms of the disease and erosive tissue damage. Taking into account the test results, a prognosis and a treatment plan are drawn up aimed at reducing the likelihood of deformities and ankylosis.

The test is not indicated for monitoring the disease or assessing the effectiveness of therapy. The concentration of antibodies does not reflect the activity of pathological processes and does not change after the use of immunosuppressants.

Preparation for analysis

The biomaterial of the study is venous blood. Its collection is carried out in morning hours, preparation for the procedure includes general rules:

1. Take a break after eating for 4-6 hours. Do not limit water consumption.
2. Avoid intense physical activity, alcohol intake, and stress factors the day before the procedure.
3. Stop smoking for 30 minutes. It is recommended to spend this time sitting and relaxing.
4. Taking medications and the need to stop them should be discussed with your doctor 7-10 days before donating blood.
5. Physiotherapeutic treatment and instrumental examinations should be carried out after the procedure for collecting biomaterial.

Blood is collected by venipuncture and serum is isolated from it before analysis. The level of AT is determined by the enzyme immunoassay; synthetic cyclic forms of citrullinated peptides are used. Preparation of final data takes 1 day.

Normal values

Normal ACCP level is 0-5 U/ml. The upper limit of reference values ​​depends on the specifics of the ELISA procedure. The norm corridor must be clarified using the results form issued by the laboratory. There are a number of comments to make when interpreting the final indicator:

• The development of RA is possible with negative result test. Sometimes ACCPs are not produced during illness.
• Hypergammaglobulinemia (increased levels of plasma immunoglobulins) may be accompanied by false-negative test data.
• An indicator within the normal range reduces the likelihood of joint erosion, but this complication cannot be completely excluded.

Increasing the indicator

The level of anti-CCP does not change under the influence of physiological factors. Reasons for increased test results include:

• Rheumatoid arthritis. The disease accounts for 98% of cases of increased rates. A significant concentration of AT is associated with a high risk of tissue destruction.
• Other autoimmune pathologies. Rarely, the AT level increases in juvenile idiopathic arthritis, SLE, scleroderma, Sjögren's syndrome, Wegener's granulomatosis, and autoimmune thyroiditis. The test result has no clinical significance.

Treatment of abnormalities

Antibodies to cyclic citrullinated peptide – early sign rheumatoid arthritis. Their high specificity and sensitivity allow the analysis to be used to identify seronegative cases of the disease (negative rheumatoid factor data), in the absence of clinical manifestations or the presence of 1-2 symptoms. As a prognostic tool, the ACCP study allows you to determine the likelihood of joint damage and select the most effective treatment regimen. To interpret the result, you must contact a rheumatologist.

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% - for the group healthy people and 97.3% - in the group of patients with diseases other than rheumatoid arthritis (ankylosing spondylitis, autoimmune thyroiditis, Crohn's disease, dermatomyositis, Epstein-Barr virus infection, 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 the medical history and clinical observations, including instrumental examination data.