Rheumatoid arthritis: diagnosis

Currently, the diagnosis of rheumatoid arthritis is based on classification criteria (1987).

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Indications for consultation with other specialists

Elderly patients, as well as when risk factors for the development of cardiovascular pathology are identified in patients of any age, are advised to consult a cardiologist.

In case of intercurrent diseases and complications of the disease or treatment (infections, diabetes, kidney pathologies with the need (biopsies, etc.) a consultation with an infectious disease specialist, purulent surgeon, endocrinologist, nephrologist, otolaryngologist and other specialists is necessary.

If there is a suspicion of the development of systemic manifestations of RA that require verification (scleritis, neurological manifestations, lung damage), a consultation with an ophthalmologist, neurologist, or pulmonologist is indicated.

An orthopedic surgeon is invited to plan prosthetics or other types of surgical treatment.

Diagnostic criteria for rheumatoid arthritis

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Morning stiffness

Morning stiffness in the joints or periarticular areas lasting at least 1 hour until maximum improvement (for 6 weeks or more)

Arthritis of three or more joint areas

Soft tissue swelling or effusion (but not bony growths) determined by a physician in three or more of the following 14 sites: proximal interphalangeal, metacarpophalangeal, wrist, elbow, knee, ankle, metatarsophalangeal joints (for 6 weeks or more)

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Arthritis of the joints of the hands

Swelling in the area of the proximal interphalangeal, metacarpophalangeal, or wrist joints (for 6 weeks or more)

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Symmetrical lesion

Simultaneous (on both sides) damage to the same joint areas of the 14 named (proximal interphalangeal, metacarpophalangeal, wrist, elbow, knee, ankle, metatarsophalangeal joints) (for 6 weeks or more)

Rheumatoid nodules

Subcutaneous nodules located over bony prominences, extensor surfaces of the limbs, or periarticular areas, as determined by the physician

Rheumatoid factor

Elevated level of RF in blood serum (determined by any method that gives a positive result in no more than 5% of healthy people)

Radiographic changes

Changes characteristic of rheumatoid arthritis on radiographs of the hands and wrists in the AP projection, including bone erosions or significant decalcification of bones in the affected joints or periarticular areas (isolated changes characteristic of osteoarthritis are not taken into account)

A patient is diagnosed with rheumatoid arthritis if at least 4 of the 7 criteria listed above are present, and it should be emphasized that the first 4 criteria must be present for at least 6 weeks.

These criteria were developed for epidemiological and clinical studies. Therefore, they lack sensitivity and specificity and cannot be used for early diagnosis of rheumatoid arthritis.

It should be noted that 5 of the 7 criteria are clinical and are identified during examination of the patient. At the same time, the need for an objective approach is clear: the swelling must be distinct, it is assessed by a doctor, while anamnestic indications and patient complaints of pain are clearly not enough.

Early diagnosis of rheumatoid arthritis

The development of a subclinical immunopathological process occurs many months (or years) before the appearance of obvious signs of the disease. According to the synovial membrane biopsy, signs of chronic synovitis are detected at the very beginning of the disease not only in inflamed but also in "normal" joints. In "conditionally" healthy people who subsequently develop rheumatoid arthritis, various immunological disorders characteristic of RA (increased levels of RF, anti-CCP antibodies, CRP) are detected long before the appearance of the first clinical symptoms of the disease.

In 2/3 of patients, structural changes (erosions) occur very quickly, already within the first two years from the onset of the disease. It has been established that preventing structural damage at the onset of RA helps to maintain the functional activity of patients in the long term. However, the period of time when active DMARD therapy can effectively slow down the progression of the lesion (the so-called "window of opportunity") is very short and sometimes amounts to only a few months from the onset of the disease.

It is obvious that rheumatoid arthritis is a striking example of a disease in which the long-term prognosis largely depends on how early the correct diagnosis was made and how early active pharmacotherapy was started. In this regard, RA to a certain extent resembles such diseases as diabetes mellitus and arterial hypertension. However, if early diagnosis of arterial hypertension and diabetes mellitus in the vast majority of cases does not present any difficulties, since it is based on the assessment of clinical manifestations well known to general practitioners and the use of available laboratory and instrumental methods, then diagnosis of rheumatoid arthritis at the onset of the disease is a much more difficult (sometimes insoluble) task. This is due to a number of objective and subjective circumstances. Firstly, the symptoms of early RA are often nonspecific, they can be observed in an extremely wide range of both rheumatic and non-rheumatic diseases, and the generally accepted classification criteria for reliable RA are not suitable for early diagnosis. Secondly, to establish such a diagnosis, special knowledge and skills in assessing clinical and radiological signs of damage are required, as well as the ability to interpret laboratory (immunological) tests, which general practitioners are not very familiar with.

Thus, one of the reasons for the unfavorable prognosis in RA is the long period of time between the onset of the disease and the patient's admission to the rheumatologist's observation. It is obvious that an important factor contributing to the improvement of the prognosis in patients with rheumatoid arthritis is the active diagnosis of this disease at the outpatient stage by general practitioners.

A group of European and American rheumatologists (under the auspices of the European League Against Rheumatism) has developed an algorithm that allows for more active detection of patients with early RA at the outpatient stage. The duration of morning stiffness (more than 10 minutes) is taken into account as a diagnostic sign of early RA (as well as an indicator of disease activity), and when examining patients, the "lateral compression test" of the metacarpophalangeal and metatarsophalangeal joints. Positive results reflect the occurrence of joint inflammation. Despite the fact that rapid progression of the lesion is more likely with high titers of rheumatoid factor, an increase in ESR and CRP levels, it should be remembered that these indicators are often normal at an early stage of the disease. In this regard, negative results of laboratory diagnostics do not exclude the diagnosis of rheumatoid arthritis, and, therefore, suggest the need to refer patients for consultation with a rheumatologist.

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Anamnesis

When collecting anamnesis, it is necessary to clarify the following information.

• Duration of symptoms.
• Duration of morning stiffness (for RA, a duration of 1 hour or more is typical; in the early stages of the disease, 30 minutes or more).
• The presence of a daily rhythm of joint pain with a characteristic increase in the early morning hours.
• Persistence of signs of damage (6 weeks or more).
• In addition, information about concomitant pathology, previous treatment, and bad habits (smoking, alcohol abuse, etc.) should be obtained. These data can influence the choice of treatment methods for rheumatoid arthritis and long-term prognosis.

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Physical examination

During a physical examination of the joints, the following parameters should be assessed.

• Signs of inflammation (swelling, deformity due to effusion, local hyperthermia of the skin).
• Pain on palpation and movement.
• Range of motion.
• The occurrence of persistent deformation due to tissue proliferation, subluxations, contractures.

Laboratory diagnostics of rheumatoid arthritis

Objectives of laboratory research.

• Confirmation of diagnosis.
• Exclusion of other diseases.
• Assessment of disease activity.
• Forecast assessment.
• Evaluation of treatment effectiveness.
• Identification of complications of the disease.

Changes in laboratory parameters detected in rheumatoid arthritis.

• Anemia (hemoglobin level less than 130 g/l in men and 120 g/l in women). An indicator of disease activity. Anemia is detected in 30-50% of cases. Any form of anemia occurs, but most often it is anemia of chronic inflammation and, less often, iron deficiency anemia. If this condition is detected, gastrointestinal bleeding must be excluded.
• Increased ESR and CRP levels. Criterion for differential diagnosis of rheumatoid arthritis and non-inflammatory joint diseases. Allows to assess the activity of inflammation, treatment effectiveness, severity of the disease, risk of progression of destruction.
• Hypoalbuminemia. Often caused by nephrotoxicity of drugs used to treat RA.
• Increased creatinine levels. Caused by nephrotoxicity of drugs used to treat RA.
• Leukocytosis (thrombocytosis, eosinophilia). An indicator of severe RA, often with extra-articular (systemic) manifestations. A combination with a high RF level is noted. Considered an indication for the appointment of GC. If this condition is detected, it is necessary to exclude the development of an infectious process.
• Neutropenia. A sign of the development of Felty's syndrome.
• Increased liver enzyme levels. An indicator of disease activity. The change may also be due to hepatotoxicity of drugs used for treatment or associated with infection with hepatitis B or C viruses.
• Increased glucose levels. Associated with the use of GC.
• Dyslipidemia. Associated with GC use, but may be due to inflammatory activity.
• Increased RF levels. Detected in 70-90% of patients. High titers at the onset of the disease correlate with the severity, rapidity of progression of the pathological process and development of systemic manifestations. However, titer dynamics do not always reflect the effectiveness of treatment. Nevertheless, the RF level is not a sufficiently sensitive and specific marker of the early stage of RA (detected at the onset in approximately 50% of patients). Specificity is also low in elderly people.
• Increased level of anti-CCP antibodies. A more specific marker of RA than the level of RF. Increased titers of both RF and anti-CCP antibodies allow diagnosing RA with higher sensitivity and specificity than an increase in the level of only one of these indicators. Detection of anti-CCP antibodies is considered a criterion for the differential diagnosis of RA at an early stage with other diseases occurring with polyarthritis (primary Sjogren's syndrome, SLE, viral hepatitis B and C, etc.). In addition, the risk of developing destruction in patients with early RA is predicted by an increase in the level of anti-CCP antibodies.
• Increased ANF levels. Detected in 30-40% of cases, usually in severe RA.
• Increased levels of immunoglobulins (IgC, IgM, IgA), concentrations of complement components. CIC. The changes are non-specific, and therefore it is not recommended to use the determination of these indicators as routine studies.
• Determination of HbA CD4. A marker of severe RA and unfavorable prognosis.
• Detection of markers of hepatitis B, C and HIV viruses. In this case, it is necessary to avoid prescribing hepatotoxic drugs.
• Changes in cerebrospinal fluid (decreased viscosity, loose mucin clots, leukocytosis (more than 6-109 l), neutrophilia (25-90%). The study has an auxiliary value. It is used for differential diagnostics of RA and other joint diseases. First of all, microcrystalline and septic inflammatory processes.
• Changes in pleural fluid | protein over 3 g/l (exudate), glucose over 8 mmol/l, lactate dehydrogenase over 1000 U/ml, pH = 7.0, RF titer over 1:320, complement level (CH50) decreased, lymphocytes (neutrophils, eosinophils)]. The study is necessary for differential diagnosis with other diseases of the lungs and pleura.

It is important to remember that laboratory tests specific for the diagnosis of rheumatoid arthritis have not been developed.

Instrumental diagnostics of rheumatoid arthritis

Instrumental diagnostics are important for confirming the diagnosis and differential diagnosis of rheumatoid arthritis.

X-ray diagnostics. X-ray of the hands and joints is necessary to confirm the diagnosis of RA, establish the stage and assess the progression of destruction. Changes characteristic of RA in other joints (at least in the early stages of the disease) are not observed. To assess the progression of joint destruction by X-ray signs, the modified Sharp method and the Larsen method are used.

Experts from the European League Against Rheumatism recommend the Parsen method when changes are assessed by several researchers. If the destruction is assessed by one specialist, it is better to use the modified Sharp method (more sensitive).

To detect subluxation of the atlantoaxial joint or cervical spondylolisthesis, it is advisable to perform an X-ray of the cervical spine.

Doppler ultrasonography. More sensitive than radiography for detecting synovitis of the knee, but not for diagnosing synovitis of small joints of the hands and feet.

MRI diagnostics. A more sensitive method for detecting synovitis at the onset of RA than radiography. Changes detected by MRI (synovitis, edema and erosion of bone tissue) allow predicting the progression of joint destruction (according to X-ray examination data). However, similar changes are sometimes detected in clinically "normal" joints, so the value of MRI for early diagnosis and prognosis of RA outcomes requires further study. In addition, MRI can be used for early diagnosis of osteonecrosis.

CT diagnostics. To detect lung lesions, it is advisable to use high-resolution CT.

Arthroscopy. Necessary for differential diagnostics of rheumatoid arthritis with nodular synovitis, arthrosis, traumatic joint injuries, etc.

Chest X-ray. Used to detect and differentiate rheumatoid lesions of the chest organs from sarcoidosis, tumors of the same localization, tuberculosis and other infectious processes.

Esophagogastroduodenoscopy. Performed in patients receiving NSAIDs and when anemia is detected.

EchoCG. Used to diagnose rheumatoid arthritis complicated by pericarditis and myocarditis, heart lesions associated with the atherosclerotic process.

Biopsy. Tissue samples (gastrointestinal mucosa, subcutaneous fat layer, gums, kidneys and other organs) are taken for examination if amyloidosis is suspected.

X-ray absorptiometry. The method is used to diagnose osteoporosis. It is used to determine the MGTC. The study of the BMD is advisable when identifying the following risk factors for the development of osteoporosis.

• Age (women over 50 years old, men over 60 years old).
• High disease activity (persistent increase in CRP level over 20 mg/l or ESR over 20 mm/h).
• The corresponding functional status is Steinbrocker stage III-IV or the HAQ (Health Assessment Questionnaire) index value of more than 1.25.
• Body weight less than 60 kg.
• Reception of GC.

The sensitivity (when three of the five criteria are detected) for the diagnosis of osteoporosis in rheumatoid arthritis is 76% in women and 83% in men, and the specificity is 54 and 50%, respectively.

Rheumatoid arthritis: differential diagnosis

The range of diseases with which rheumatoid arthritis must be differentiated is very wide.

Most often, the need for differential diagnostics arises at the onset of the disease with joint damage in the form of mono- and oligoarthritis. In this case, it is necessary, first of all, to pay attention to such typical signs of RA as the symmetry of arthritis, predominant damage to the joints of the hands with impairment of their functions, the development of an erosive process in the joints of the hands, detection of RF and, especially, anti-CCP antibodies.