Autoantibodies to nuclear antigens (ANA Screen IFT)
Why this test?
For the diagnosis of systemic connective tissue diseases.
For differential diagnosis of rheumatic diseases.
To evaluate the effectiveness of therapy for autoimmune diseases.
To monitor the course of systemic connective tissue diseases.
In what cases is it prescribed?
With symptoms of an autoimmune disease (long-term fever, joint pain, fatigue, weight loss, skin changes).
When changes characteristic of systemic connective tissue diseases are detected (increased ESR, C-reactive protein level).
Determination of antinuclear factor (ANF) is the gold standard for detection of antinuclear antibodies (ANA) and diagnosis of autoimmune diseases.
The pathogenesis of systemic diseases of connective tissue (SZST) is closely related to disorders in the immune system and increased production of antibodies to the structures of one's own cells. Autoantibodies to the components of the cell nucleus - antinuclear antibodies - interact with nucleic acids and proteins of the nucleus, antigens of the cytoplasm, which is manifested by inflammatory changes in tissues and organs, pain in the joints and muscles, pronounced fatigue, weight loss, skin changes. ANAs are found in many autoimmune diseases, but are most characteristic of systemic lupus erythematosus (SLE). ANA occurs in more than 90% of patients with systemic diseases of the connective tissue, currently about 200 varieties are described, which are united by a single name - antinuclear factor.
When determining ANF by the method of indirect fluorescence, the line of human larynx adenocarcinoma epithelial cells HEr-2 is more often used. НЕр-2 cells are a very convenient substrate for laboratory research, as they have large nuclei and grow in a single layer on glass. ANAs are detected when binding to intracellular antigens of HEr-2 cells.
In the study, epithelial cells НЕр-2 are grown on glass, fixed and incubated with diluted blood serum of the patient. After removal of excess serum, the cells are incubated with fluorescein-labeled antibodies, then washed again and examined using a fluorescent microscope. At the same time, the titer of antibodies and the type of glow are determined. A titer of more than 1:160 is considered diagnostically significant. During an exacerbation of rheumatic diseases, it exceeds 1:640, and during remission it decreases to 1:160-1:320. The more antibodies, the higher the titer. According to the type of glow, it is possible to establish the targets of antinuclear antibodies, which is of important clinical importance and determines the tactics of further examination of the patient. The main ones are peripheral, granular (fine/large), nucleolar, centromeric, and cytoplasmic types of nuclear staining. Each type of glow has very characteristic features that allow you to distinguish one option from another.
Homogeneous (diffuse) staining is associated with the presence of antibodies to double-helical DNA, histones and is characteristic of SLE and lupus drugs.
Peripheral glow is due to the peripheral distribution of chromatin in the nucleus, associated with antibodies to DNA and specific for SLE. It is important to differentiate this type of glow from staining of the nuclear membrane, which occurs in autoimmune liver diseases.
Granular (dotted, reticulated) staining occurs most often and is the least specific, it is found in many autoimmune diseases. Autoantigens in this case are nucleoprotein complexes in the nucleus (Sm, U1-RNP, SS-A, SS-B antigens and PCNA).
Very high titers of ANF with a macrogranular type of glow often indicate mixed connective tissue disease.
Nuclear (nuclear) staining is due to the formation of antibodies to the components of the nucleolus (PC polymerase-1, NOR, U3RNP, PM / Scl), is detected in scleroderma, Sjögren's disease. ANA sometimes increases in endocrine diseases (type 1 diabetes, thyroiditis, thyrotoxicosis, polyendocrine syndrome), skin diseases (psoriasis), during pregnancy, after organ and tissue transplantation, in patients on hemodialysis.
Centromeric glow appears in the presence of antibodies to the centromere of chromosomes and is characteristic of the form of scleroderma - CREST syndrome.
The cytoplasmic type of glow is associated with antibodies to tRNA synthetase, in particular to Jo-1, which is characteristic of dermatomyositis and polymyositis. This type of staining is also determined in the presence of antibodies to other components of the cytoplasm in autoimmune hepatitis, primary biliary cirrhosis.
Simultaneous detection of different types of luminescence indicates the presence of different types of antibodies.
In healthy individuals, a fine-grained glow may be detected with low, moderate, or high ANA titers, but normally coarse-grained or homogeneous types of glow should not be detected.
Depending on the results of the assessment of the type of glow, further patient treatment tactics are developed and additional studies are prescribed to clarify the spectrum of ANA.