Rheumatoid factor in the blood - what does it mean: increased, decreased, normal

Detailed description of the study

Rheumatoid factor (RF) is a group of antibodies to human tissues that are formed as a result of disorders in the immune system. The name of these antibodies explains their frequent detection in rheumatoid arthritis. However, RF may be elevated in other rheumatic and inflammatory diseases. Detection of RF is an important part of the diagnostic search when determining the causes of joint inflammation and confirming the presence of rheumatoid arthritis. This disease of an autoimmune nature develops mainly in women over 40-50 years of age. The reasons for it have not yet been sufficiently studied. The role of genetic and hormonal factors in combination with the adverse effects of the external environment is assumed. The formation of various antibodies to joint tissues leads to inflammation in them. Mostly small joints of the hands and feet are affected, inflammation is accompanied by redness and pain, and impaired motor activity. An important diagnostic sign of rheumatoid arthritis is stiffness in the limbs after waking up, which goes away within an hour. Chronic inflammation of the joints ultimately leads to their destruction and deformation of the hands and feet. RF is detected in more than 75% of patients with rheumatoid arthritis. Its titer weakly correlates with disease activity, but patients with high titers tend to have more severe rheumatoid arthritis. Sjögren's syndrome is a disease in which there is also an increase in RF levels. It is based on progressive damage to the salivary and lacrimal glands due to their erroneous destruction by the human immune system. Violation of salivary secretion is manifested by dry mouth, destruction of the lacrimal glands - dry eyes. There is insufficient hydration of the skin and mucous membranes. In addition, high RF titers can be found in a number of other diseases, which include: systemic lupus erythematosus, polymyositis, tuberculosis, syphilis, viral hepatitis, infectious mononucleosis, subacute septic endocarditis, autoimmune hepatitis and other autoimmune liver lesions. An increase in RF titer is sometimes observed among healthy people over 60 years of age, as well as during pregnancy and after blood transfusions (especially in the case of frequent blood transfusions). For a more accurate diagnosis of rheumatoid arthritis, it is recommended to determine not only the RF, but also the antibody titer to the cyclic citrulline-containing peptide. The use of both tests increases diagnostic sensitivity.

How to prepare for research

Basic rules of preparation:

• Blood is donated from a vein in the morning on an empty stomach; before the test you must refrain from eating for 8-12 hours.
• Do not drink any drinks (coffee, tea, etc.). Before the analysis, you can only drink clean water.
• Avoid alcohol and smoking for 24 hours before blood collection;
• Do not eat fatty, spicy, smoked, or other “heavy” foods the day before the test.
• Be sure to inform your doctor about the drugs you are constantly using, as they may affect the test result.

References

1. Chaltsev, B. D., Vasiliev, V. I., Palshina S. G. [etc.]. Clinical guidelines for the diagnosis and treatment of Schörgen's disease with anticentromere antibodies. Scientific and practical rheumatology, 2019. 2. Rheumatoid arthritis. Clinical recommendations. approved Ministry of Health of Russia, 2021. - URL: https://legalacts.ru/doc/klinicheskie-rekomendatsii-revmatoidnyi-artrit-utv-minzdravom-rossii/ (access date: 02/11/2021). 3. Croia, C, Bursi, R, Sutera, D, One year in review 2021: pathogenesis of rheumatoid arthritis. Clinical Experience in Rheumatology, 2021.

Rheumatoid factor in the blood - what does it mean?

In medicine, rheumatoid factor is a collection of abnormal antibodies (immunoglobulins) that are produced by the cells of the intraarticular membrane and synovial fluid of the joints. Later, the spleen, lymphoid tissue and bone marrow are connected to the synthesis. The pool of abnormal immunoglobulins is 90% represented by IgM-RF. The remaining 10% includes IgA-RF, IgE-RF and IgG-RF.

The pathological mechanism of RF synthesis is triggered by certain diseases and malfunctions of the immune system. Having formed in the joints, rheumatoid factor penetrates into the blood, where it begins to behave like an antigen. It binds to its own class G immunoglobulins, forming immune complexes with them.

The resulting compounds penetrate the bloodstream into the joint cavities, where they settle on the synovial membranes. There they cause the development of cytotoxic reactions, causing inflammation and leading to the gradual destruction of the joints. RF tends to settle on the vascular endothelium, causing damage. RF levels in blood and synovial fluid usually correlate.

Qualitative determination of rheumatoid factor is based on the ability of abnormal antibodies to react with the Fc fragment of IgG. The latter is a unique marker of chronic inflammatory processes, past infections, autoimmune disorders, and cancer.

Almost all healthy people have a small amount of abnormal antibodies in their blood. They are not detected by qualitative tests, which are positive only when the RF is above 8 IU/ml. According to various sources, a level of rheumatoid factor in the blood of less than 10-20 U/ml is considered normal.

Normal RF values ​​may vary slightly between laboratories. This is due to the use of various equipment and chemical reagents. Therefore, each laboratory indicates reference indicators on the forms. These are the ones you need to focus on when assessing the results of the analysis.

Latex test

The simplest, cheapest and fastest test for which an RF latex reagent containing human IgG is used. Blood serum is taken as the test material. The abnormal immunoglobulins it contains react with the Fc fragments of IgG that are in the reagent.

If the serum contains more than 8 U/ml of rheumatoid factor, a pronounced agglutination reaction occurs (the gluing of normal and pathological immunoglobulins to each other). Visually it can be seen as a positive test. The duration of the study is about 15-20 minutes.

The latex test has its drawbacks. These include low information content and a high frequency of false positive results. Unlike quantitative methods, the latex test does not make it possible to detect the level of RF in the blood plasma.

How to get tested for rheumatic tests

Blood for rheumatological examination is taken from a vein. To determine the three main markers (rheumatic factor, ASLO and C-reactive protein), it is enough to submit biological material once. The serum is divided into several parts to determine all the necessary parameters. If there are changes in the ASLO marker (suspicion of rheumatism), the test must be taken again after 7 days (the dynamics of the disease are monitored).

If necessary, a study of additional indicators (albumin, total protein, CEC) may be prescribed. In this case, you will need to donate blood several times - separately for a rheumatic test and for an additional biochemical test.

How long the analysis is done depends on the laboratory. Typically, the results are prepared within 1 working day, and the patient can find out them the next day after the material is collected.

Norms by age

When assessing indicators, international units (IU) are used for each milliliter of blood. For brevity, they are simply called units.

Adequate values ​​depend on gender, general health, and age. The issue should be considered in more detail.

For the female part of humanity, the results vary within small limits, as shown in the table:

Over the years, the rate of rheumatoid factor in women becomes slightly higher. But at the level of statistical error.

For adult men, everything is about the same:

During childhood, norms vary quite a lot:

You won't be able to decipher the results yourself. Since an increase in the concentration of rheumatoid factor is possible in healthy people. Spontaneously, for no apparent reason.

For example, after intense physical activity. There are many options. It is worth entrusting the interpretation to doctors.

Determination methods

Methods for determining RF are divided into qualitative and quantitative . The first include the latex test and the classical Waaler-Rose reaction, which is practically no longer used. These tests make it possible to detect with some certainty an increase in rheumatoid factor.

To accurately detect the level of RF, quantitative determination (nephelometric or turbidimetric) is used. An even more advanced test is ELISA - enzyme-linked immunosorbent assay. It allows you to detect the concentration of not only IgM-RF, but also other pathological immunoglobulins. This opens up new diagnostic possibilities and makes the analysis more informative.

Indications for biochemical blood test for Russian Federation

An RF test is necessary for people whose doctors suspect the presence of joint diseases, systemic connective tissue diseases, immune disorders, chronic inflammatory processes, malignant neoplasms, and helminthic infestations. In children, determination of RF is necessary if juvenile rheumatoid arthritis is suspected.

Before donating blood, you should consult with your doctor. He will clarify the price of the study and tell you how much it takes to complete, what it shows. Having received the results, he will decipher them and choose tactics for further action. Perhaps the doctor will make a final diagnosis or prescribe additional tests.

Chronic pain is a direct indication for testing.

Determination of RF is indicated when the following symptoms appear:

• periodic arthralgia - pain in the joints of any localization;
• constant increase in body temperature to 37-38 degrees;
• daily morning joint stiffness;
• causeless pain in muscles, abdomen, lower back;
• the appearance of minor hemorrhages or rashes of a non-allergic nature on the skin;
• hyperkeratosis - excessive thickening of the skin in different parts of the body;
• pathological dryness of the skin, eyes, oral mucosa;
• sudden loss of body weight, constant weakness and apathy.

The listed symptoms may indicate degenerative-destructive joint diseases or systemic autoimmune diseases. Rash and petechiae on the skin are common signs of vasculitis; pathological dryness of the skin and mucous membranes often indicates Sjogren's syndrome.

In addition to a blood test for rheumatoid factor, doctors may order other tests. A complete examination of the patient includes general and biochemical blood tests, urinalysis, fluorography, and x-ray examination of the joints in which the person feels stiffness or pain.

Reasons for a negative result

There are situations when the Russian Federation is not detected at all. From a formal point of view, this is the norm. Exactly the same as the minimal deviations in clinical indicators.

On the other hand, there are cases when the pathological autoimmune process has already begun, but there are no changes in the laboratory analysis. This is how rheumatoid arthritis manifests itself in the early stages.

The first indications may appear after several weeks or even months. Up to six months. Only then does gradual or rapid growth begin.

The absence of rheumatoid factor in the blood (negative result) is a variant of the clinical norm. There is no need to worry about this, quite the contrary.

Rheumatoid factor for rheumatism

In almost all patients with rheumatism, the amount of rheumatic factor in the blood is within normal limits. Its increase can be observed with the development of secondary infective endocarditis. There are cases where an increase in the level of RF occurred several years before the appearance of rheumatism. A reliable connection between these two events has not yet been established.

In ankylosing spondylitis and systemic scleroderma, the RF is usually within normal limits. In rare cases, its concentration in the blood may increase: this occurs with massive damage to peripheral joints.