Antinuclear antibodies are a category of autoantibodies that, when reacted with the nuclei of body cells, begin to destroy them. Therefore, the study of ANA is considered a rather sensitive marker in the diagnosis of autoimmune disorders, most of which are accompanied by lesions of the connective tissue. Some of the types of antinuclear antibodies are also found in diseases of non-immune origin: inflammatory, infectious, malignant, etc.
What pathologies are specific to?
The most specific antinuclear antibodies to the following pathologies:
- Systemic lupus erythematosus is a connective tissue and skin disease.
- Dermatomyositis - damage to muscles, skin, skeletal tissue, etc.
- Scleroderma - thickeningconnective tissue.
- Periarteritis nodosa is an inflammatory process affecting arterial vascular walls.
- Rheumatoid arthritis - damage to the connective tissue and joints.
- Sjögren's disease - tissue damage with glandular manifestations (decrease in the secretion of the salivary and lacrimal glands).
When is antinuclear antibody screening positive?
Autoimmune pathologies
Autoimmune pathologies, when the immune system starts an attack on its own cell tissues, are considered the most dangerous in clinical medicine. Most autoimmune diseases are classified as chronic and can cause serious dysfunction of internal organs.
One of the common tests used in diagnosing various autoimmune conditions is the test for the level of antinuclear antibodies (antinuclear), which is carried out in three ways:
- ELISA method, which determines the total level of antibodies;
- reaction method of indirect immunofluorescence RNIF, through which up to 15 types of antibodies can be detected;
- immunoblotting method.
Antinuclear antibody immunoblot
This is a laboratory test of blood for the presence of antibodies to HIV. It is a more accurate analysis than ELISA and is used to confirm the ELISA result. Immunoblotting (western blot) is used in the diagnosis of HIV infections, determining the level of antinuclear antibodies, inas an auxiliary expert method, which is designed to confirm the result of the ELISA. As a rule, positive ELISA results are double-checked with this method, as it is considered more specific and sensitive.
Immune blotting combines enzyme immunoassay with electrophoretic gel separation of viral proteins and their transfer to nitrocellulose membranes. Immunoblot consists of several stages. First, the purified and destroyed protein is subjected to electrophoresis, in which the antigens included in its composition are divided into molecules. Then, by blotting, the antigens are transferred from the gel onto a nylon filter strip or nitrocellulose, which contain a specific spectrum of proteins.
Next, the test material is applied to the strip, and if specific antibodies are present in the sample, they begin to bind to the antigen strips corresponding to them. The result of such interaction is made visible. The presence of stripes in some areas of the strip confirms the presence of antibodies to certain antigens in the examined blood. Immunoblotting is often used to confirm HIV infection. Blood sera are considered positive if antibodies to two HIV envelope proteins are detected by immunoblotting. If the screening is positive, then the body is developing a specific autoimmune disease.
Possible diseases
Antinuclear antinuclear antibodies can be observed in more than 1/3 of patients with recurrent chronic hepatitis. In addition, the level of ANA may increase in case of development of the following pathologies:
- infectious mononucleosis (a viral disease that causes massive damage to internal organs);
- leukemia (malignant blood disease) in acute and chronic forms;
- hemolytic anemia (anemia due to the destruction of red blood cells);
- Waldenström's disease (affects the bone marrow);
- cirrhosis of the liver (chronic pathology associated with changes in the structures of the liver tissue);
- malaria;
- leprosy (infection of the skin);
- chronic kidney failure;
- thrombocytopenia (decreased platelet production);
- lymphoproliferative pathologies (tumors in the lymphatic system);
- myasthenia gravis (muscle fatigue);
- thymoma (tumor of the thymus).
Immunoglobulin levels
Simultaneously with the assessment of the level of antinuclear antinuclear antibodies during the analysis, the level of immunoglobulins is assessed: IgM, IgA, IgG. The detection of such components in the blood may indicate a high risk of collagenosis and rheumatic diseases.
In cases where a link between the level of antibodies and symptoms in a patient is found, the presence of antinuclear antibodies in the blood itself is a diagnostic feature and may influence the choice of therapeutic technique for a particular disease. Preservation of a high concentration of antinuclear antibodies during a long coursetherapy indicates an extremely unfavorable prognosis for the patient. A decrease in values against the background of ongoing therapy may indicate a period of remission or an impending death.
In addition, antinuclear antibodies can be detected in he althy people in 3-5% of cases - up to 65 years, and in 37% of cases - after 65 years.
Indications for determining the level of ANA
Antinuclear factor testing is necessary in the following cases:
- in the diagnosis of autoimmune and other systemic diseases without severe symptoms;
- in the complex diagnosis of systemic lupus erythematosus, its stage and form, as well as in the choice of therapeutic tactics and prognosis;
- in the diagnosis of drug-induced lupus;
- when preventive examination of patients with lupus erythematosus;
- in the presence of specific symptoms: prolonged fever without a specific cause, pain and aches in muscles, joints, skin rashes, high fatigue, etc.;
- if there are symptoms of systemic pathologies: damage to internal organs or skin, arthritis, convulsions, epileptic seizures, fever, fever;
- when prescribing drug therapy with hydralazine, disopyramide, propafenone, ACE inhibitors, procainamide beta-blockers, propylthiouracil, lithium, chlorpromazine, carbamazepine, isoniazid, phenytoin, hydrochlorothiazide, minocycline, statins, as there is a possibility of drug-induced lupus erythematosus.
Doctor's consultation
In addition to a general practitioner, it is possible to consult and receive a referral for research from such narrow specialists:
- dermatovenereologist;
- rheumatologist;
- nephrologist.
What is the norm for anti-nuclear antibodies?
Deciphering the results, pathological and normal indicators
Normally, antinuclear antibodies in plasma are usually absent or detected in small amounts. The result depends on the test execution method:
1. ELISA:
- less than 0.9 points – normal (negative);
- 0, 9-1, 1 points - doubtful result (recommended to retest after 14 days);
- more than 1, 1 point - positive result.
2. For the analysis of RNIF, a titer of less than 1:160 is considered a normal result.
3. On immunoblotting, the norm is “not detected.”
In what situations can an antinuclear antibody test be positive?
What factors can affect the result?
The list of factors that contribute to the distortion of laboratory results includes:
- violation of the norms of preparation for analysis or venipuncture algorithm;
- taking pharmacological drugs (Methyldopa, Carbamazepine, Penicillamine, Nifedipine, Tocainide, etc.);
- The presence of uremia in a patient often gives a false negative result.
Interpretation of the results is carried out in a complex manner. Determine an accurate diagnosisbased on a single diagnostic test is not possible.
Preparation
Venipuncture is performed on an empty stomach in the morning (8 hours should pass from the moment of eating). You can only drink water. It is not recommended to use nicotine substitutes and smoke before blood sampling. On the eve and on the day of the study, you can not drink energy and alcoholic drinks, do physical work and worry. 15 days before testing, in agreement with the doctor, the use of medications (antiviral and hormonal agents, antibiotics, etc.) is canceled. To obtain the correct result, the analysis is recommended to be repeated after 2 weeks.
We considered that this is a screening for anti-nuclear antibodies.
