If we speak in a language that is understandable to the public, arthritis is damage to the joints. Arthritis can be either an independent disease (for example, rheumatoid arthritis, spondylitis) or a manifestation of another disease (for example, rheumatism).
In rheumatology, it is customary to divide arthritis into two main groups:
1. Inflammatory arthritis
2. Degenerative arthritis - arthrosis
Arthralgia (joint pain) is also considered separately. When palpating the joints, no objective changes are observed in them.
If you suspect any form of arthritis, it is recommended to contact a rheumatologist, who will prescribe the necessary examination to confirm or rule out this disease.
What tests are done for arthritis:
Let's take a closer look at what blood indicators you need to pay attention to in arthritis.
In chronic arthritis, anemia may occur due to prolonged inflammation:
To diagnose rheumatoid arthritis (RA), the severity of this type of anemia corresponds to the severity of the inflammatory process
In patients with Rheumatoid Arthritis with signs of anemia, systemic manifestations are more common than in patients with Reactive Arthritis, although in the latter, anemia is detected more often. Most likely, this is due to the fact that with ReA (reactive arthritis), an acute inflammatory reaction is pronounced and a large number of anti-inflammatory cytokines are released.
ESR is a very important, although not the most important indicator in the diagnosis of arthritis. In a healthy person, ESR should not normally exceed 10 mm/h (in men) and 15 mm/h (in women). In rheumatic diseases, ESR increases very much, up to 40-60 mm/h.
A biochemical blood test for arthritis includes a set of special tests to confirm an autoimmune disease, along with other studies and instrumental diagnostics.
Determining the concentration of CRP in blood serum is an important step in the diagnosis of arthritis. In a healthy person, its concentration does not exceed 0.002 g/l, and in autoimmune pathologies, the value of CRP reaches 0.01 g/l and higher. The concentration of C-reactive protein increases during the activity of ankylosing spondylitis.
During autoimmune inflammatory processes in the blood, the concentration of plasma protein fractions changes - dysproteinemia develops.
A significant increase in the concentration of the β-globulin fraction is observed with the development of:
ELISA and PCR determine the presence of antibodies to previous infections. Thanks to these tests, it is possible with a 100% guarantee to either confirm the presence of infection or refute it, long before the clinical manifestation of the disease. These highly sensitive tests play an important role in the diagnosis of infectious arthritis (eg, Reiter's disease).
What other tests for arthritis need to be taken and what to pay attention to.
The results of this analysis are important for the diagnosis of arthritis. However, it is not always possible to rely only on this analysis. The fact is that changes in the synovial fluid can be a consequence of injuries, bruises of the joints. Therefore, the rheumatologist makes the decision to conduct a study of synovial fluid based on the available results of other studies.
The main thing to pay attention to in the analysis results:
Significant changes in urinalysis parameters are observed only in severe forms of the disease, mainly with prolonged systemic autoimmune inflammatory process.
This disease is characterized by chronic inflammatory processes in the joints and systemic bone erosion with subsequent damage to organs. The disease occurs after chronic infections, due to the weakness of the immune system and genetic characteristics. Most often occurs in women under 55 years of age.
The main problem of this disease is that the immune system mistakenly mistakes body tissues for harmful ones and begins to fight them, as a result of which the initial signs of rheumatoid arthritis appear.
In the early stages, rheumatoid arthritis has no obvious signs, so months may pass from the onset of the disease in the body to its detection. But when the disease becomes more advanced and serious signs begin to appear, it is much more difficult to fight it. For this reason, despite the complexity, one should try to determine the diagnosis at an early stage.
To determine rheumatoid arthritis, it is important to know what the most common signs are:
The presence of one or two of these symptoms cannot be the basis for making a diagnosis. This especially applies to older people, for whom some signs are characteristic based on age. For final conclusions, it is necessary to have a clinical picture that excludes the possibility of other causes of inflammation.
To create this picture, the American College of Rheumatology set out diagnostic criteria for rheumatoid arthritis in 1987. Their accuracy is in the range of 91-93%. At the moment, this is one of the most likely schemes, however, it cannot always determine the diagnosis when the early stage of the disease occurs. The following criteria exist:
Doctors diagnose rheumatoid arthritis only if at least four signs are detected simultaneously. It is also taken into account that other diseases that affect the joints cannot exclude rheumatoid arthritis. Only after this does treatment begin.
Even laboratory diagnosis of this disease cannot be as accurate as possible, but it is precisely in it that there are such concepts as rheumatoid factor, the severity of anemia and ESR in a blood test. Also, studies on ACCP are increasingly being carried out. Taken together, they give a very realistic idea of the disease and a fairly accurate prognosis of its further course. When treatment is carried out, the main indicator of its success is the assessment of the activity and effectiveness of DAS28.
As already mentioned, one of the main indicators is rheumatoid factor. We note that its data cannot be used as the main criteria for making a diagnosis. There is a reason for this: rheumatoid factor can appear simultaneously with other diseases. In addition, it is present in 5% of healthy people, and this figure increases with age. Therefore, only a third of people who have been diagnosed with rheumatoid factor are diagnosed with rheumatoid arthritis. Its presence can be used for prognostic purposes using CRP and ACCP. If a certain titer is high, then the disease is severe, progresses rapidly and has extra-articular manifestations.
In recent years, research on antibodies to cyclic citrullinated peptide has begun to develop. At the moment, this is the most effective method for determining the diagnosis, with a specificity of almost 100%. Of the 100 people who were found to have antibodies to cyclic citrullinated peptide, 80 were actually diagnosed with rheumatoid arthritis.
Diagnosis is made by determining the number of ACCPs that correlate with the main indicators of rheumatoid arthritis. These include:
ESR - erythrocyte sedimentation rate - is an indicator of the level of inflammation in the body. It is determined by the rate of entry of red blood cells into the test tube for measurements. In healthy people, ESR levels are low, but when inflammation occurs, it increases.
CRP is a test for C-reactive protein, which also provides information about inflammation, but is considered more effective than ESR. Patients have high CRP levels. A CRP test can help monitor how treatment is progressing and how the body responds to certain criteria. The DAS28 activity scale is used for CRP calculations.
Based on the fact that according to the DAS28 scale, CRP in sick people was higher by 185%, and ESR by 39.5%, conclusions are drawn that the presence of ACCP is characteristic of high RA activity. DRR has more precise criteria, so it is calculated first.
If the disease becomes severe, normocytic anemia begins. You should get a blood test as soon as possible. Such complications correspond to an increased platelet count and severe anemia. Leukocytes during the illness do not exceed the norm, in rare cases there may be slight leukocytosis, mainly with Felty's syndrome. Possible eosinophilia and increased ESR, which can also be determined by doing a blood test.
When undergoing a biochemical blood test, you need to pay attention to the level of ceruloplasmin and active proteins. Exceeding their norm indicates a high rate of disease progression. This blood test provides auxiliary indicators, without which treatment is less effective.
All changes in synovial fluid are recorded and serve to identify rheumatoid arthritis. With this disease, the fluid is usually cloudy and has low viscosity with elevated protein levels but low glucose levels. In this case, most of the leukocytes consist of neutrophils, the total number of which ranges from 50 μl(-1) to 5,000 μl(-1). The leukocytes themselves are approximately 2,000 μl(-1), but their number is characteristic of different forms of arthritis and is not significant when diagnosing rheumatoid arthritis. In addition, immune complexes are formed in the synovial fluid, which sharply reduce the hemolytic activity of complement and the level of C3, C4.
This diagnostic method is not particularly effective in the initial stages. At this time, x-rays may reveal nothing more than soft tissue swelling or effusion in the joint cavity, but they can also be detected during a physiological examination. To identify early signs of joint damage, you can undergo an MRI examination or caste scintigraphy using 99mTc-distaphonate.
As rheumatoid arthritis progresses, X-ray tests can tell more about the signs and symptoms, but very little about the specific disease due to their lack of specificity. The only thing that can be determined by taking an x-ray is the location of the changes and how symmetrical they are.
The meaning of X-ray diagnostics is different - to examine organs for the presence of bone erosion and the level of cartilage destruction. This serves as an indicator of whether the treatment is proceeding correctly and how to continue it further. X-rays are performed using several methods (Steybrocker, Larsen, Sharp), each of which has certain criteria:
An X-ray is necessary to determine internal abnormalities in order to more accurately prescribe effective treatment.
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Diagnosing rheumatoid arthritis (RA) is a rather difficult task for specialists of any profile. In the typical clinical course of the disease, making a diagnosis usually does not cause difficulties, but the variety of variants of this pathology does not always allow one to suspect and diagnose the disease in a timely manner.
It is especially difficult to diagnose the disease at an early stage, when the symptoms are very nonspecific (for example, a slight increase in body temperature, weakness, fatigue), there is no typical symmetrical polyarthritis and characteristic radiological changes, and laboratory indicators do not always clearly indicate this disease.
Diagnosis in the advanced stage of the disease is based on a combination of a number of signs and criteria. So, first of all, experts pay attention to the combination of chronic symmetrical polyarthritis (that is, damage to several joints at once), characteristic changes on X-rays (erosions, periarticular osteoporosis) and positive laboratory tests.
There are so-called diagnostic criteria for rheumatoid arthritis that allow you to reliably make this diagnosis. These criteria are:
The presence of a MINIMUM 4 of the 7 presented criteria makes the diagnosis of RA reliable! In addition, criteria 1-4 inclusive must be observed in the patient for AT LEAST 6 weeks!
More modern and reliable are the 2010 American College of Rheumatology (ACR) diagnostic criteria for rheumatoid arthritis, which are a scoring system where each symptom and sign is assigned a score, which are then summed up. These criteria are:
A. Joint damage:
B. RF and ACDC tests:
C. Increased ESR and C-reactive protein:
D. Duration of presence of symptoms:
The presence of at least 6 points from all categories (AD) makes the diagnosis reliable!
These diagnostic criteria “work well” in the presence of extensive, pronounced symptoms of the disease. But it has long been proven that the most effective treatment results can be achieved precisely at the early stages of RA. For this reason, diagnosing the early signs of this pathology is one of the most important and difficult tasks of modern rheumatology. However, “working” criteria for diagnosing early rheumatoid arthritis have been developed:
In the diagnosis of rheumatoid arthritis, both instrumental and laboratory examination methods are important. The most important and modern marker of this pathology is the determination of ACCP (antibodies to cyclic citrullinated peptide). The discovery of this indicator in patients with RA was an important milestone in the development of effective diagnosis of the disease, therefore today it is ACCP that is the most sensitive and specific laboratory criterion for the disease.
Great importance is attached to the determination of ACCPs also because they are very useful in diagnosing the early manifestations of arthritis. ACCP have a high specificity for this disease, so a positive test for ACCP is highly likely to support this diagnosis, while other markers, which will be discussed below, may give a false positive result in other diseases or be completely negative. An increase in ACCP of more than 5 Units/ml reliably indicates in favor of RA (confidence of about 70-80%).
It is necessary to pay attention to changes in tests for rheumatoid arthritis, an increase in ESR, C-reactive protein, changes in the general blood test are important (pay attention to the following indicators: the number of red blood cells and hemoglobin, leukocytes, platelets). All these changes are nonspecific, that is, they indicate the presence of some kind of inflammatory process (any) in the body and can only lead to the idea of arthritis.
More informative in diagnosis is the determination of rheumatoid factor (RF) in blood serum and joint fluid. However, it should be remembered that RF may be absent (seronegative form of RA) or appear later, at later stages. In addition, it can give a false positive result in older people and in other chronic diseases (for example, chronic hepatitis, thyroiditis, etc.). The presence of only a positive rheumatoid factor does not give the doctor the right to unambiguously diagnose rheumatoid arthritis, however, if there is also a corresponding clinical picture in the form of typical polyarthritis, it makes this diagnosis reliable.
Other indicators of inflammation such as antinuclear antibodies and LE cells may also be detected in some patients. When examining synovial (joint) fluid, pay attention to the following changes: increased leukocyte content, increased protein, decreased glucose concentration.
Among the methods of instrumental diagnostics, radiography of the affected joints is important. X-ray changes are quite typical, which made it possible to distinguish the so-called X-ray stages of rheumatoid arthritis:
Determining the radiological signs of arthritis allows you to prescribe appropriate treatment and predict the prognosis of the disease. However, the most reliable method of visualizing joints is, of course, magnetic resonance imaging (MRI). Thus, MRI can detect signs of rheumatoid arthritis even before pronounced changes on X-ray (the so-called pre-radiological stage). The study reveals a kind of “bone edema”, which is a harbinger of erosions in this disease.
Ultrasound examination of joints is most informative in the presence of fluid (effusion) in the joints, that is, synovitis.
With the development of extra-articular lesions in this disease, the following diagnostic methods are important: ultrasound of internal organs, echocardioscopy, radiography or CT of the chest, etc.
Rheumatoid arthritis is differentiated from other inflammatory diseases of the joints (reactive arthritis and arthropathy, spondyloarthritis), systemic lupus erythematosus, systemic scleroderma, osteoarthritis, gout. If you suspect rheumatoid arthritis, you should immediately consult a rheumatologist.
Rheumatoid factor (RF) is a group of autoantibodies of various classes (IgA, IgM, IgG) that interact with the Fc fragment of the human IgG immunoglobulin molecule. In some pathological conditions, human immune cells produce antibodies against their own IgG class immunoglobulins. This ultimately leads to the formation of immune complexes that attack the layer of the joint capsule.
In laboratory diagnostics, manufacturing companies mainly produce kits that determine the IgM class. Recently, tests have appeared that determine rheumatoid factor using immunoglobulin A (RF IgA, Rheumatoid factor IgA, RF IgA). It is believed that a comprehensive determination of rheumatoid factor by IgM and IgA increases the specificity of the study aimed at diagnosing rheumatoid arthritis. The definition of rheumatoid factor as one of the criteria for diagnosing rheumatoid arthritis was introduced already in 1958. In this case, any method for determining the RF was used. This was the first (until recently) and main test in the laboratory diagnosis of rheumatoid arthritis. Biochemical testing for RF has always been considered important, especially in the early stages of the disease, when detection of this factor was the only objective way to confirm clinical data. Sometimes a relatively long period passes before the onset of pronounced clinical manifestations of rheumatoid arthritis, and the atypical course makes diagnosis difficult. In such cases, laboratory diagnosis of RA represents an important tool for differential diagnosis.
The test for rheumatoid factor is considered negative if the results do not exceed the established norm. If the results exceed the norm, but do not exceed it 3 times, then the test is considered low positive and is scored 2 points. Exceeding results by more than three times is interpreted as highly positive and is assessed with 3 points. A high content of RF factor indicates a high risk of erosive arthritis. It is believed that rheumatoid factor has high sensitivity in advanced rheumatoid arthritis (about 90%), but low specificity - about 60%.
After numerous studies, it turned out that rheumatoid arthritis can occur in both seropositive and seronegative forms. This means that the production of rheumatoid factor does not always accompany the course of RA. It has been shown that rheumatoid factor appears in the blood of sick people in 60-80% of cases (seropositive form). At the same time, the absence of RF in the presence of clinical signs does not exclude the presence of rheumatoid arthritis (seronegative form). In modern criteria used in the differential diagnosis of RA, the definition of rheumatoid factor has not lost its significance; it is only strengthened by new modern achievements in biochemistry and immunology. These new tests are anti-citrullinated peptide antibodies (ACCP), anti-citrullinated vimentin antibodies (anti-MCV) and anti-keratin antibodies (AKA). The determination of antibodies to citrullinated peptide, along with the determination of RF, was included in the international criteria for diagnosing RA, adopted in 2010.
It should be taken into account that the appearance of RF in 5% of cases is recorded in healthy individuals. This trend increases with patient age. The mechanism of these processes is not clear. The rather low specificity of the test (about 60%) must be taken into account. This means that approximately 40% of the tests will be positive in the absence of rheumatoid arthritis. In some cases, the appearance of rheumatoid factor may result from other diseases - cancer, inflammatory diseases caused by viruses and bacteria (infectious mononucleosis, hepatitis C, syphilis, tuberculosis, cytomegaly), other autoimmune diseases (Sjögren's syndrome, systemic lupus erythematosus), diffuse connective tissue diseases (dermatomyositis, scleroderma), autoimmune liver diseases.
Federal clinical guidelines
Laboratory diagnosis of rheumatic diseases
Definition of rheumatic diseases
Laboratory markers of inflammation
Methods used to collect/select evidence:
search in electronic databases
Description of methods used to collect/select evidence:
The evidence base for recommendations is systematic reviews in the latest available version of The Cochrane Library, Medline database, PubMed (systematic reviews (meta-analyses), randomized clinical trials, cohort studies or case-control studies, review articles. Search depth 10 years.
Methods used to assess the quality and strength of evidence
Rating of importance according to the rating scheme
Levels of evidence adopted in developing these recommendations
a high-quality meta-analysis, systematic review of RCTs, or a large RCT with a very low likelihood of bias, the results of which can be generalized to the relevant Russian population.
high-quality (++) review or systematic review of cohort or case-control studies, or
high-quality (++) cohort or case-control study with very low levels of bias, or
RCT with a low (+) risk of bias, the results of which can be generalized to the relevant Russian population.
cohort study or case control study or controlled study without randomization with a low level of systematic error (+), the results of which can be generalized to the relevant Russian population or
RCTs with a very low or low (+) risk of bias, the results of which cannot be directly generalized to the relevant Russian population.
description of a case series or
uncontrolled study or
Clinical informativeness of laboratory tests
The clinical informativeness of laboratory tests is determined by calculating the operational characteristics of the test (diagnostic sensitivity and specificity - DC and DS, predictive value of positive and negative results, likelihood ratio of positive and negative results - LPR and LPR) and using ROC analysis. The most useful laboratory tests for diagnosing RD are those with LRPR>5 and LRLR<0.2; useful – with OPPR>2 and ?5, OPPR>0.2 and ?0.5; those with no benefit - with OPPR?2 and OPPR>0.5.
Good Practice Points ( GPPs )
Recommended good practice is based on the clinical experience of members of the guideline development group
No economic analysis was carried out and publications on pharmacoeconomics were not analyzed
Recommendation validation method:
External peer review
Internal peer review
Definition of rheumatic diseases
According to the modern classification, rheumatic diseases (RD) belong to the continuum of human immunoinflammatory diseases, in the pathogenesis of which autoimmunity and autoinflammation associated with genetically determined and induced environmental factors (infections, smoking, etc.) defects in the activation of the acquired and innate immune response play a key role.
1. The main goal of laboratory diagnosis of RD is to obtain objective information about the presence and nature of immunopathological changes in the examined patient, which is an important tool for early diagnosis, assessment of activity, severity, prognosis of the disease and the effectiveness of therapy ( A )*.
3. An important task of standardization of laboratory diagnostics of RD is the comparison and harmonization of immunological tests with international and national reference materials (certified reference materials) and research methods, databases on reference limits of analyzed biomarkers, algorithms for assessing the results obtained ( A ).
4. A central place in the laboratory diagnosis of RD is occupied by serological tests associated with the detection of circulating autoantibodies ( A ). A comment. Positive autoantibody results are among the diagnostic criteria for systemic RD; used to assess the activity and prognosis of these diseases; play an important role in diagnosing RD at an early stage; allow identification of individual clinical and laboratory subtypes of RD; serve as predictors of the development of autoimmune RD in asymptomatic patients.
5. In autoimmune RDs, autoantibody testing is carried out primarily to confirm the diagnosis in patients with an insufficient number of clinical manifestations. Detection of autoantibodies in the absence of clinical signs is not sufficient to make a diagnosis of an autoimmune disease (A) . A comment. There has been an increase in the frequency of detection of autoantibodies in elderly and senile people, while taking medications, with viral and bacterial infections, malignant neoplasms, and in healthy relatives of patients with autoimmune diseases .
6. When assessing the clinical significance of autoantibodies, it is necessary to take into account the persistence and severity of their overproduction ( D ) . A comment. In infections, moderate transient formation of autoantibodies is observed, and in autoimmune diseases, persistent, pronounced overproduction is observed.
7. Autoantibodies specific to only one RD are very rare. Autoimmune diseases are characterized by the simultaneous presence of several types of autoantibodies in one serum, the so-called autoantibody profile, the assessment of which significantly increases the diagnostic value of determining these biomarkers ( B ) . A comment. Standard autoantibody profiles have been developed for the diagnosis of systemic RD (Table 2).
Standard autoantibody profiles for the diagnosis of systemic RDs
Antinuclear factor (ANF), aDNA, aSm, aRo/SS-A, aLa/SS-B, aRNP, antibodies to cardiolipin – aCL, aC1q
IgM/IgA RF, antibodies to citrullinated proteins - ACCP, AMCV, AKA, ACE, antifilagrin antibodies, antibodies to Ra 33, BiP (P-68)
IgG/IgM aCL, IgG/IgM antibodies to ? 2 -glycoprotein I – huh? 2 -GPI, lupus anticoagulant - VA)
aScl-70, anticentromere antibodies (ACA), antinucleolar antibodies (aTh/To, aRNA polymerase III, aPM-Scl, aU1 RNP, antibodies to fibrillarin - aU3 RNP)
Antibodies to tRNA aminoacyl synthetases - Jo-1, PL-7, PL-12, EJ, OJ, KS; antibodies to SRP, Mi-2, PM-Scl, KJ)
tsANCA, pANCA, antibodies to proteinase 3 and myeloperoxidase
ANF, antibodies to smooth muscle (SMA), liver and kidney microsomes type I - LKM1, liver cytoplasmic antigen LC-1, soluble liver/pancreas antigen SLA/LP, mitochondria - AMA-M2
Inflammatory bowel diseases (Crohn's disease, ulcerative colitis)
IgG/IgA antibodies to Saccharomyces Cerevisiae – ASCA, pANCA, atypical ANCA
8. Nonspecific immune disorders (hyperimmunoglobulinemia, decreased complement concentration) may indirectly indicate the development of systemic RD and serve as indications for the study of autoantibodies (C) .
9. The main diagnostic laboratory markers of RD are antinuclear antibodies (ANA), rheumatoid factor (RF), antibodies to citrullinated proteins (ACP), antineutrophil cytoplasmic antibodies (ANCA), antiphospholipid antibodies (APL) (A) . A comment. A list of primary (screening), secondary (confirmatory) and additional serological tests for the diagnosis of autoimmune RDs has been developed (Table 3). C screening tests should have a high DC, and confirmatory tests should have a high DC.
10. The most useful markers of the acute phase response in RD are ESR and C-reactive protein (CRP) (A) . A comment. According to RCT data, cohort and descriptive studies, ESR and CRP allow one to evaluate the inflammatory activity of the disease, the nature of progression and prognosis of the outcomes of the chronic inflammatory process, as well as the effectiveness of anti-inflammatory therapy .
Algorithm for laboratory diagnosis of autoimmune rheumatic diseases
11. Other laboratory biomarkers of RD (cytokines, markers of endothelial activation, immunoglobulins, immune complexes, cryoglobulins, components of the complement system, lymphocyte subpopulations, genetic markers, indicators of bone and cartilage metabolism, markers of apoptosis, etc.) have less clinical significance compared to autoantibodies and indicators of the acute phase of inflammation ( C ). A comment. May be useful for monitoring disease activity and response to treatment (descriptive studies)
Antinuclear antibodies (ANAs) are a heterogeneous group of autoantibodies that react with various components of the nucleus.
The “gold standard” and primary screening method for determining ANA in blood serum is the indirect immunofluorescence reaction (IDIF) using cryostat sections of mouse or rat liver (kidneys) or HEp-2 cells (human epithelial laryngeal cancer epithelial cells) as a substrate. . When ANAs are tested by NRIF, they are traditionally designated as antinuclear factor (ANF). Evaluation of the results of NRIF is carried out indicating the maximum titer of detection of ANF in the test sera, as well as the intensity and type of immunofluorescence. The nature of the glow reflects the presence of various types of ANA, to a certain extent specific for a number of autoimmune diseases (Table 4) (A) .
Association with diseases
Antibodies to DNA (double and single stranded), DNP, histones (H1, H2A, H2B, H3, H4)
SLE, drug-induced lupus, any autoimmune rheumatic diseases and non-rheumatic diseases
Antibodies to double-stranded, native DNA (aDNA)
Antibodies Sm, RNP, SS-A/Ro, SS-B/La, Jo-1
SLE, CTD, Sjögren's syndrome, PM/DM
Antibodies to Scl-70
SSD (diffuse form)
Anticentromere antibodies (ACAs)
CREST syndrome, Raynaud's syndrome
Antibodies to RNA polymerase 1, PM/Scl, U3RNP
Other screening methods for determining ANA (enzyme-linked immunosorbent assay - ELISA, new methods of solid-phase analysis, including multiplex diagnostic platforms based on microparticles), which establish the presence of antibodies to a mixture of nuclear antigens in sera, increase the percentage of false-negative and false-positive results and cannot replace ANA testing using NRIF (A) .
In patients with positive results of ANF determination, it is recommended to conduct confirmatory tests for specific ANAs to individual nuclear antigens (nDNA, Sm,SSA/Ro,SSB/La,Scl-70, RNP), using ELISA, immunoblot (IB), double immunodiffusion methods ( DID), counter-immunoelectrophoresis (CIEF), etc. (A) . Some types of ANA (anticentromere, PCNA, antibodies to the mitotic apparatus of the cell - NUMA) are detected only by the NRIF method on HEp-2 cells, which eliminates the need for their further study using confirmatory tests (A) .
3. Normal serum ANF titers are <1:40 when using cryostat sections of the liver or kidneys of laboratory animals and <1:160 when using HEp-2 cells (A) .
3. ANF testing is very useful for the diagnosis of SLE (DS: 93%, DS: 57%, LRPR: 2.2, LR: 0.11) (positive detection of ANF serves as a diagnostic criterion for SLE) (A) and SSc (DS: 85%, DS:54%, LR:1.86, LR:0.27) (A) , useful for diagnosing SS associated with SLE (A) (DS:48%, DS:52%, LR:0, 99, ORR: 1.01), and less useful for the diagnosis of PM/DM (DS: 61%, DS: 63%, ORR: 1.67, ORR: 0.61) (A) . ANF positivity is considered as a diagnostic criterion for drug-induced lupus, CTD, and autoimmune hepatitis (A).
4. ANF is a very useful marker for assessing the prognosis and monitoring the course of juvenile chronic arthritis in combination with uveitis (A) and secondary Raynaud's phenomenon associated with systemic RD (A) .
5. Positive results of ANF determination have no proven diagnostic and prognostic value in RA, multiple sclerosis, thyroid diseases, infections, idiopathic thrombocytopenic purpura and fibromyalgia (A/B) . .
6. The recommended frequency for determining ANF is once every 6 months – 1 year ( D ) .
Antibodies to deoxyribonucleic acid (DNA) are divided into two main types: antibodies that react with double-stranded (native) DNA (dsDNA) and antibodies that react with single-stranded (denatured) DNA (ssDNA).
1. Antibodies to DNA are a serological marker of SLE. Antibodies to dsDNA are more specific for the diagnosis of SLE than antibodies to ssDNA, which are present in the sera of patients with other cancers and do not have significant diagnostic value (A).
2. Standard methods for determining antibodies to dsDNA in blood serum are ELISA, NRIF using Crithidialuciliae as a substrate, and RIA (Farr test) (A) . The primary screening test for detecting antibodies to dsDNA is the ELISA (A) . Using ELISA, both low and high avidity antibodies to dsDNA are determined, which causes less specificity of this test compared to other methods. Along with this, a large number of false-positive results when using ELISA can be caused by contamination of dsDNA with ssDNA molecules and spontaneous denaturation of dsDNA to form sDNA. ELISA detects IgG and IgM antibodies to dsDNA, with IgG antibodies to dsDNA having the greatest clinical significance. If anti-dsDNA antibody ELISA results are positive, confirmatory tests are recommended, including NRIF and the Farr method, which have lower sensitivity but higher specificity for diagnosing SLE (A) . The NRIF method using the simplest flagellated microorganism Crithidialuciliae is based on the interaction of antibodies to dsDNA with the kinetoplast of the flagellum, which has a giant mitochondrion containing a large number of circular dsDNA molecules not associated with histone proteins. The NRIF method detects IgG and IgM antibodies to dsDNA with medium avidity. The Farr method, based on the precipitation of [3H]-DNA labeled with anti-dsDNA antibodies using a saturated ammonium sulfate solution, allows the measurement of high avidity anti-dsDNA antibodies.
3. The normal level of antibodies to dsDNA when testing sera using ELISA is < 10-20 IU/ml (depending on the manufacturer of commercial reagent kits), NRIF with Crithidialuciliae - < 1:10, Farr method < 7 IU/ml (B) .
4. Anti-dsDNA antibody testing is very useful for diagnosing SLE in patients with positive ANF results (DS: 57.3%, DS: 97.4%, LRPR: 44.6, LRPR: 0.49) (A) . The presence of antibodies to dsDNA is a mandatory diagnostic criterion for SLE.
5. Determination of antibodies to dsDNA in SLE is useful for assessing the activity of the pathological process (DP: 66.0%, DS: 66.0%, ODPR: 4.14, OPPR: 0.51) (A) and kidney damage (DS - 86.0%, DS - 45.0%, OPPR - 1.7, OPOR - 0.3) (A) .
6. Positive results of detection of antibodies to dsDNA do not reliably predict exacerbations of SLE (A) .
7. In other diseases, testing antibodies to dsDNA is not useful, since they are detected very rarely (≤5% of cases) and in low titers (A) .
8. The recommended frequency for determining antibodies to dsDNA is once every 3 months (B) .
Antibodies to histones
Histones are the main protein components of the cell nucleus, which are divided into 5 classes (H1, H2A, H2B, H3, H4).
1. Standard methods for determining antibodies to histones in blood serum are ELISA and IB ( B ).
2. The ULN of antibodies to histones when testing sera using ELISA is ? 40 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).
3. Determination of antibodies to histones is in some cases useful for diagnosing drug-induced lupus ( D ). A comment. According to descriptive studies, antibodies to histones are most often detected in drug-induced lupus induced by procainamide and hydralazine (DI: 50-100), but can be detected in patients taking these drugs but without symptoms of lupus (DI: 44%), and in patients with SLE (DC: 50-80%). The DS of antibodies to histones is 86% [29-31].
4. The recommended frequency for determining antibodies to histones is once every 6 months to 1 year.
Antibodies to nucleosomes (antichromatin antibodies, antibodies to DNP, LE-cell factor) interact with epitopes of the H2A-H2B-DNA complex.
1. Standard methods for determining antibodies to nucleosomes in blood serum are ELISA, IB, LE-cell test (B).
2. The ULN of antibodies to nucleosomes when testing sera using ELISA is ? 20 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).
3. Determination of IgG antibodies to nucleosomes can be useful for the diagnosis of SLE (DS: 46-81%, DS: 95-100%) (C) and drug-induced procainamide-induced lupus (DS: 77%, DS: 86-99% ) (WITH) . Detection of antibodies to nucleosomes is associated with kidney damage in SLE (C) and the development of autoimmune hepatitis type 1 (C) .
4. The recommended frequency for determining antibodies to nucleosomes is once every 6 months to 1 year ( D ) .
Antibodies to extractable nuclear antigens (ENA) bind to water-soluble nuclear antigens and are divided into antibodies to Sm, U1RNP, Ro/SSA, La/SSB, Scl-70 and Jo-1.
1. As a primary screening test for identifying antibodies to EJA, it is recommended to determine ANF using the NRIF ( A ) . According to international standards, if the results of the ANF study are positive, two or more confirmatory tests are carried out for the presence of antibodies to EJA, including ELISA, DID, CIEF and IB ( A ) . ELISA has high sensitivity, but lacks specificity and is used to screen for antibodies to EJA in ANF-positive patients, followed by testing of sera using less sensitive but more specific methods (IB, CIEF, DID) ( A ) . The disadvantage of the IB method is its lower sensitivity compared to ELISA and CIEF, as well as the ability to detect antibodies predominantly to linear epitopes ( A ) .
Sm antigen consists of 5 small nuclear (sn) RNAs (U1, U2, U4, U5, U6) associated with 11 or more polypeptides (70kd, A, B/B?, C, C?, D, E, F, G ). In SLE, do antibodies to Sm react with B/B? and D polypeptides common to U1, U2, U4/U6 snRNPs involved in pre-mRNA splicing.
1. Standard methods for determining antibodies to Sm in blood serum are ELISA, IB, DID and CIEF.
2. The ULN of antibodies to Sm when testing sera using ELISA is ? 25 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).
3. Positive results for the determination of antibodies to Sm are a specific serological marker and diagnostic criterion for SLE (DS: 8-20%, DS: 99%) (A), but are not useful for assessing the activity and characterization of disease subtypes (A) .
4. A single determination of antibodies to Sm ( D ) .
Antibodies to U 1RNP react with the protein components (70kDa, A and C) of U1 small nuclear ribonucleoprotein (U1 snRNP).
1. Standard methods for determining anti-U1RNP antibodies in blood serum are ELISA, IB, DID and CIEF (A).
2. The ULN of antibodies to U1RNP when testing sera using ELISA is ? 25 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).
3. Detection of antibodies to U1RNP in high titers is useful for diagnosing CTD (DC: 95-100%, DS: 98%) (A) ; less useful for diagnosing SLE (DC - 30%, DS - low) (B) ; useful for predicting the unfavorable course of SLE with the development of severe damage to internal organs (B). In the sera of 60% of patients with positive results for determining antibodies to U1RNP, antibodies to Sm are detected.
4. The recommended frequency for determining antibodies to U1RNP is once every 3 months (B) .
SS-A/Roantigen – polypeptides of 60kDa and 52kDa, forming a complex with RoRNA (hY1, hY3 and hY5).
1. Standard methods for determining anti-SS-A/Ro antibodies in blood serum are ELISA, IB, DID and CIEF (A).
2. The ULN of antibodies to SS-A/Ro when testing sera using ELISA is ? 25 units/ml; antibodies to SS-A/Ro-52kDa and SS-A/Ro-60kDa? 10 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).
3. Antibodies to SS-A/Ro are found in the sera of 40-80% of patients with SS and 30-50% of patients with SLE. In 50% of patients with SS and SLE, antibodies react with the 60kDa and 52kDa proteins, in 40% of patients with SS - only with the 52kDa protein, and in 20% of patients with SLE - only with the 60kDa protein of the SS-A/Ro (B/C) .
4. Positive results of detection of antibodies to SS-A/Ro are diagnostic criteria for primary and secondary SS (A) .
5. During pregnancy, a study of the serum level of antibodies to SS-A/Ro-52kDa and SS-B/La-48kDa is useful for predicting the risk of developing complete transverse heart block in the fetus, antibodies to SS-A/Ro– to predict the risk of developing neonatal lupus-like syndrome in newborns (B) .
6. In patients with SLE, positive results of testing antibodies to SS-A/Ro are associated with photosensitivity, SS, and hyperproduction of RF (B) .
7. The recommended frequency for determining antibodies to SS-A/Ro is once every 3 months ( D ) .
SS-B/La antigen is a nucleocytoplasmic complex of 48kDa phosphoprotein cRoRNA (hY1-hY5), which is a terminal transcription factor for RNA polymerase III.
1. Standard methods for determining antibodies to SS-B/La in blood serum are ELISA, IB, DID and CIEF (A).
2. The ULN of antibodies to SS-B/La when testing sera using ELISA is ? 25 U/ml (depending on the recommendations of the manufacturer of commercial reagent kits) ( C / D ).