Antinuclear antibodies are a category of autoantibodies that, when reacted with the nuclei of the body's cells, begin to destroy them. Therefore, the study of ANA is considered a fairly sensitive marker in the diagnosis of autoimmune disorders, most of which are accompanied by connective tissue lesions. Some of the varieties of antinuclear antibodies are also found in diseases of non-immune origin: inflammatory, infectious, malignant, etc.
What pathologies are specific?
The most specific antinuclear antibodies to the following pathologies:
- Systemic lupus erythematosus is a disease of connective tissue and skin.
- Dermatomyositis - damage to muscles, skin, skeletal tissue, etc.
- Scleroderma is a densification of connective tissue.
- Periarteritis nodosa is an inflammatory process that affects the arterial vascular walls.
- Rheumatoid arthritis - damage to the connective tissue and joints.
- Sjogren’s disease - damage to tissues with glandular manifestations (decreased secretion of salivary and lacrimal glands).
When is antinuclear antibody screening positive?
Autoimmune pathologies
Autoimmune pathologies, when the immune system starts an attack on its own tissue, are considered the most dangerous in clinical medicine. Most autoimmune diseases are classified as chronic and can provoke serious dysfunctions of the internal organs.
One of the common tests used in the diagnosis of various autoimmune conditions is a study on the level of antinuclear antibodies (antinuclear), which is carried out in three ways:
- enzyme-linked immunosorbent assay ELISA, which determines the overall level of antibodies;
- RNIF indirect immunofluorescence reaction method, by which up to 15 types of antibodies can be detected;
- immunoblotting method.
Antinuclear antibody immunoblot
This is a laboratory blood test for HIV antibodies. It is a more accurate analysis than ELISA, and is used to confirm the result of ELISA. Immunoblotting (western blot) is used in the diagnosis of HIV infections, determining the level of antinuclear antibodies, as an auxiliary expert method, which is designed to confirm the result of ELISA. As a rule, this technique recheck the positive results with ELISA, as it is considered more specific and sensitive.
Immune blotting combines an enzyme-linked immunosorbent assay with electrophoretic separation of viral proteins in a gel and their transfer to nitrocellulose membranes. Immunoblot consists of several stages. First, the purified and destroyed protein undergoes electrophoresis, in which the antigens that make up it are divided into molecules. Then, the antigens are transferred from the gel to the strip of nylon filter or nitrocellulose, which contain a specific spectrum of proteins, by blotting.
Next, the test material is applied to the strip, and if specific antibodies are present in the sample, they begin to bind to the corresponding bands of antigens. The result of this interaction is made visible. The presence of bands in some sections of the strip confirms the presence of antibodies to specific antigens in the blood tested. Immune blotting is often used to confirm HIV infection. Positive are blood serums in which antibodies to two HIV envelope proteins are detected by immune blotting. If the screening is positive, it means that a certain autoimmune disease develops in the body.
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 if the following pathologies develop:
- infectious mononucleosis (a viral disease in which massive damage to the internal organs occurs);
- leukemia (malignant blood disease) in acute and chronic forms;
- hemolytic anemia (anemia due to the destruction of red blood cells);
- Waldenstrom disease (affects the bone marrow);
- cirrhosis of the liver (chronic pathology associated with a change in the structures of the liver tissue);
- malaria;
- leprosy (infection of the skin);
- chronic renal failure;
- thrombocytopenia (decreased platelet production);
- lymphoproliferative pathologies (tumors in the lymphatic system);
- myasthenia gravis (muscle fatigue);
- thymoma (thymus tumor).
Immunoglobulin Level
Simultaneously with the assessment of the level of antinuclear antinuclear antibodies, the level of immunoglobulins: IgM, IgA, IgG is assessed during the analysis. The detection of such components in the blood may indicate a high risk of collagenosis and rheumatic diseases.
In cases where the relationship between the level of antibodies and the symptomatology of the patient is detected, the presence of antinuclear antibodies in the blood itself is a diagnostic sign and may affect the choice of a therapeutic technique for a particular disease. Maintaining a high concentration of antinuclear antibodies with a long course of therapy indicates an extremely poor prognosis for the patient. A decrease in values against the background of ongoing therapy may indicate a period of remission or an approaching death.
In addition, antinuclear antibodies can be fixed in healthy 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
Investigate the antinuclear factor 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 selection of therapeutic tactics and making a prognosis;
- in the diagnosis of drug lupus;
- during preventive examination of patients with lupus erythematosus;
- in the presence of specific symptoms: prolonged fever for no specific reason, pain and aching in the muscles, joints, skin rashes, high fatigue, etc .;
- in the presence of 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, since there is a chance of red blood cell.
The doctor's consultation
In addition to a general practitioner, it is possible to consult and get directions for research from such narrow specialists:
- dermatovenerologist;
- rheumatologist;
- nephrologist.
What is the norm of antinuclear antibodies?
Interpretation of results, pathological and normal indicators
Normally, antinuclear antibodies in the plasma, as a rule, are absent or are determined in small quantities. The result depends on the test execution method:
1. IFA method:
- less than 0.9 points - the norm (negative);
- 0.9-1.1 points - a dubious result (it is recommended to conduct a second test after 14 days);
- more than 1.1 points - a positive result.
2. For a RNIF analysis, a titer of less than 1: 160 is considered a normal result.
3. In 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 standards for preparation for analysis or venipuncture algorithm;
- taking pharmacological preparations (Methyldopa, Carbamazepine, Penicillamine, Nifedipine, Tokainid, etc.);
- the presence of uremia in a patient often gives a false negative result.
The interpretation of the results is comprehensive. It is impossible to determine the exact diagnosis based on a single diagnostic study.
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. Before blood sampling, it is not recommended to use nicotine substitutes and smoke. On the eve and on the day of the study, you can not drink energy and alcoholic beverages, engage in physical work and worry. 15 days before the test, in consultation with the doctor, the medication (antiviral and hormonal drugs, 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 antinuclear antibodies.