The Antinuclear Antibody (ANA) test is used as the primary test to assess the patient's condition for autoimmune connective tissue disorders. These are disorders that affect many tissues and organs throughout the body. What do the test results show? What are ANAs? What diseases can the ANA test detect?

Contents:

  1. ANA test - what are antinuclear antibodies?
  2. ANA test - use in diagnostics
  3. ANA test - the presence of ANA in the blood of he althy people
  4. ANA test - what is the name?
  5. ANA test - when should the ANA test be done?

The abbreviationANAcomes from the English name anti-nuclear antibodies, which translates into Polish as "antinuclear antibodies". These molecules belong to proteins called autoantibodies, i.e. those that attack the organism that produces them.

ANA test - what are antinuclear antibodies?

The human body has many defense mechanisms against pathogens. One of them is humoral immunity. It is based on the production of protective antibodies. In he althy people, the immune system produces antibodies to foreign antigens.

Sometimes, however, there are situations where autoantigens are produced, which are directed against proteins in our own body. This process is essential for the genesis of autoimmune diseases.

Antinuclear antibodies attack proteins and other molecules that make up the nucleus.

There are many different types of ANA. The breakdown of these antibodies is based on the types of nuclear components against which these molecules are directed. Depending on the type, ANAs can bind to both single proteins and complex complexes.

For example, there are antibodies against nuclear channels and histones, i.e. molecules on which DNA is wound.

The attacking ANA can be distinguished:

  • DNA
  • histony
  • ribonucleoproteins
  • Nuclear RNA
  • non-histone proteins

All these components are specific to the cell nucleus.

ANAs are present in the blood during various diseases. This includes autoimmune disorders, cancer, and some types of infections. This allows forthe use of antinuclear antibodies in the diagnosis of certain disease states.

ANA test - use in diagnostics

The ANA test is used to detect antinuclear autoantibodies in the patient's blood. This test is important for the diagnosis of diseases such as:

  • systemic lupus erythematosus
  • Sjögren's band
  • scleroderma
  • polymyositis
  • dermatomyositis
  • autoimmune hepatitis
  • drug reaction-induced rolling

A positive ANA test result is diagnostic only if there are clinical signs that confirm it. Antinuclear antibody testing may also be useful for monitoring disease progression.

Typical tests used to detect and evaluate ANA are:

  • indirect immunofluorescence
  • ELISA-enzyme immunosorbent test

Indirect immunofluorescence method

Indirect immunofluorescence is one of the most widely used tests for the presence of ANA. Typically, this test uses Hep-2 cells. They are applied in the form of a thin layer on microscope slides. Then the serum collected from the patient is placed on them and incubated with Hep-2 cells.

If ANA is present in the sample taken, it is detected after the incubation period in a form associated with the antigens in the cell nucleus. This can be seen by adding a fluorescent label that binds to the antibodies.

Fluorescein or rhodopsin B isothiocyanate (FITC) or rhodopsin B are most often used for this purpose. A molecule fluoresces when it is hit by a beam of light of a specific wavelength. A microscope is used to observe and evaluate the fluorescence.

Different patterns of fluorescence can be observed depending on the type of antibody present in human serum and the antigen localization in HEp-2 cells. Their analysis allows to determine the types of antibodies present in the sample.

Antibody levels are determined by making serial dilutions of blood serum. The ANA test is considered positive if fluorescence is observed at a titer of 1:40/1: 80. However, a result greater than 1: 160 is of significant diagnostic importance.

Enzyme-linked immunosorbent assay (ELISA)

The enzyme immunoassay (ELISA) uses microtiter plates in which antigens for the detection of ANA are placed. Each well of the plate is coated with either one or more antigens. This is to detect specific antibodies.

The blood serum is incubated inplate wells and then rinsed out of them. If antinuclear antibodies were present in the sample, they will remain bound to the appropriate antigens on the microtiter plate after washing.

In the next step of the test, a second enzyme-bound antibody is added to the well in the plate. The enzymatic reaction causes the color of the solution to change.

The difference in color is proportional to the amount of antigen-bound antibody in the well of the plate. The color of the obtained solution can be assessed by the spectrophotometric method, i.e. by measuring the intensity of the light beam transmitted through the solution.

ANA test - the presence of ANA in the blood of he althy people

It is estimated that in 5% of the human population, antinuclear antibodies are present in the blood at concentrations considered to be diagnostically significant, regardless of the presence of the disease state.

As the frequency of ANA increases with age, as many as 10-37% of he althy people over the age of 65 test positive for the presence of ANA. Such cases are more common in women than in men.

ANA test - what is the name?

The characteristic value for the ANA test is the titer. It indicates the degree of dilution of the serum at which the antinuclear antibodies become undetectable. The higher the concentration of ANA in the blood, the higher the titer present in the test results.

If the titer is above 1: 160, it is advisable to perform a specificity test of the antinuclear antibodies. These additional tests should be performed in conjunction with the patient's clinical history analysis and physical examination. The goal of these steps is to diagnose or rule out autoimmune disorders.

It should be noted, however, that such a result occurs in 5% of patients, regardless of the disease state. The test result is diagnostic only when there are other disease symptoms.

A negative ANA test result indicates that the patient is unlikely to have lupus or other autoimmune disease.

ANA test - when should the ANA test be done?

The ANA test is ordered when the patient's symptoms indicate a systemic autoimmune disorder. They can be very non-obvious and nonspecific, as well as change over time.

Examples of symptoms are:

  • Low fever
  • Persistent fatigue
  • Arthritis-like pain
  • Red rash
  • Skin sensitivity to light
  • Hair loss
  • Muscle pain
  • Numbness or tingling in the hands or feet
  • Inflammation of organs and tissues (kidneys, lungs, heart, heart lining, central nervous systemnerve or blood vessels)
About the authorSara Janowska, MA in pharmacyPhD student of interdisciplinary doctoral studies in the field of pharmaceutical and biomedical sciences at the Medical University of Lublin and the Institute of Biotechnology in Białystok. A graduate of pharmaceutical studies at the Medical University of Lublin with a specialization in Plant Medicine. She obtained a master's degree defending a thesis in the field of pharmaceutical botany on the antioxidant properties of extracts obtained from twenty species of mosses. Currently, in his research work, he deals with the synthesis of new anti-cancer substances and the study of their properties on cancer cell lines. For two years she worked as a master of pharmacy in an open pharmacy.

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