Behterev's disease: diagnosis

Early diagnostics of Bechterew's disease involves analyzing information about the presence of diseases associated with HLA-B27 in the patient's immediate relatives. And information about the presence of episodes of uveitis, psoriasis, signs of chronic inflammatory bowel diseases in the past is important for conducting a more detailed examination of the patient and determining the form of the disease.

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Clinical diagnostics of Bechterew's disease

Particular attention should be paid to assessing the condition of the spine, joints and entheses, as well as those organs and systems that are usually affected by AS (eyes, heart, kidneys, etc.).

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Diagnosis of Bechterew's disease: examination of the spine

They evaluate posture, curves in the sagittal (cervical and lumbar lordosis, thoracic kyphosis) and frontal planes (scoliosis). They measure the range of motion.

To assess movements in the cervical spine, the patient is asked to consistently perform maximum flexion and extension (the norm is not less than 35°), lateral bends (the norm is not less than 45°) and head turns (the norm is not less than 60°).

Movements in the thoracic spine are assessed using the Ott test: 30 cm are measured down from the spinous process of the 7th cervical vertebra and a mark is made on the skin, then the patient is asked to bend down as much as possible, bending his head, and this distance is measured again (normally the increase is at least 5 cm). The respiratory excursion of the chest is also measured to assess the mobility of the costovertebral joints (the norm for adult men in young and middle age is at least 6 cm and at least 5 cm for women).

The mobility of the lumbar spine in the sagittal plane is assessed using the Wright-Schober test. With the patient standing, mark the point at the intersection of the midline of the back with an imaginary line connecting the posterior superior iliac spines. Then, 10 cm above the first, mark the second point. The patient is asked to bend forward as much as possible without bending the knees. In this position, measure the distance between the two points. Normally, it increases by at least 5 cm. The range of motion in the frontal plane is determined by measuring the distance from the floor to the tip of the middle finger with the patient standing, and then during maximum strict lateral flexion of the torso in both directions (without bending the knees). The distance should decrease by at least 10 cm.

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Examination of joints

Describe the appearance (presence of defiguration), determine pain on palpation and the range of motion in all peripheral joints. Particular attention should be paid to the joints of the lower extremities, as well as the temporomandibular, sternoclavicular, sternocostal joints and the articulation of the manubrium of the sternum with its body.

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Entheses

The attachment sites of tendons and ligaments in the areas where pain is noted are assessed by palpation (the presence of local pain). Enthesitis is most often detected in the area of the iliac crest, ischial tuberosities, greater trochanters of the femurs, tuberosities of the tibia, and the area of the heels (bottom and back).

It has long been noted that in many patients, laboratory parameters traditionally used to assess the activity of systemic inflammation (ESR, CRP, etc.) do not change significantly. For this reason, to assess the activity of this disease, they are mainly guided by clinical parameters: the severity of pain syndrome and stiffness in the spine, joints and entheses, the presence of systemic manifestations, the degree of effectiveness of NSAIDs prescribed in a full daily dose, as well as the rate of progression of functional and radiographic changes in the spine. For a quantitative assessment of the overall activity of AS, the BASDAI index (Bath Ankylosing Spondilitis Disease Activity Index) is widely used. The questionnaire for determining the BASDAI index consists of 6 questions that the patient answers independently. A 100-mm visual analogue scale is provided to answer each question (the left extreme point corresponds to the absence of a given symptom, the right extreme point corresponds to the extreme degree of severity of the symptom; for the last question about the duration of stiffness - 2 hours or more).

1. How would you rate your level of general weakness (fatigue) over the past week?
2. How would you rate the level of pain in your neck, back or hip joints over the past week?
3. How would you rate the level of pain (or degree of swelling) in your joints (other than your neck, back or hips) over the past week?
4. How would you rank the degree of discomfort you experience when touching or pressing on any painful areas (over the past week)?
5. How would you rate the severity of morning stiffness after waking up (over the past week)?
6. How long has your morning stiffness after waking up lasted (over the past week)?

Using a ruler, measure the length of the marked line segments. First, calculate the arithmetic mean of the answers to questions 5 and 6, then add the resulting value to the results of the answers to the remaining questions and calculate the average value of the sum of these five values. The maximum value of the BASDAI index is 100 units. A BASDAI index value of 40 units or more indicates high disease activity. The dynamics of this index is considered a sensitive indicator of treatment effectiveness.

To quantitatively assess the degree of functional impairment in AS, the BASFI (Bath Ankylosing Spondilitis FunctionaІ Index) is used. The questionnaire for determining this index consists of 10 questions, each of which is accompanied by a 100-mm scale. The leftmost point corresponds to the answer "easy", and the rightmost point - "impossible". The patient is asked to answer all the questions, making a mark with a pen on each scale.

During the last week, were you able to do the following?

1. put on socks or tights without assistance or devices (an assistive device is any object or device that is used to facilitate the performance of an action or movement):
2. bend forward, bending at the waist, to pick up the handle from the floor without the help of equipment;
3. reach with your hand, without outside help or devices, UP TO a HIGH shelf;
4. get up from a chair without armrests, without leaning on your hands, without outside help or devices;
5. get up from the floor from a supine position without outside help or any devices;
6. stand without support or additional support for 10 minutes without experiencing discomfort;
7. climb up 12-15 steps without leaning on the railing or cane, placing one foot on each step;
8. turn your head and look behind you without turning your torso;
9. engage in physically active activities (e.g. exercise, sports, gardening):
10. maintain activity throughout the day (at home or at work).

Using a ruler, measure the length of the marked line segments and calculate the arithmetic mean of the answers to all questions. The maximum value of the BASFI index is 100 units. Functional disorders are considered significant if the value of this index exceeds 40 units.

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Laboratory diagnostics of Bechterew's disease

There are no specific laboratory parameters that are important for diagnosing Bechterew's disease. Although HLA-B27 is detected in more than 90% of patients, this antigen is often detected in healthy people (in the Caucasian population in 8-10% of cases), so its determination has no independent diagnostic value. In the absence of HLA-B27, ankylosing spondylitis cannot be ruled out. When HLA-B27 is detected, the probability of the disease increases only in cases where, based on the clinical picture, there are certain suspicions of the presence of this disease (for example, characteristic pain in the spine, family history), but obvious radiographic signs of sacroiliitis are not yet present.

Laboratory diagnostics of Bechterew's disease allows to determine the indicators of activity of the systemic inflammatory process, in particular the content of CRP in the blood and ESR, which are increased less than in patients with a clinically active form of the disease. The degree of increase in laboratory indicators of systemic inflammation is usually small and poorly correlates with clinical indicators of disease activity and the effect of therapy, therefore, for assessing the course of the disease and the results of treatment, laboratory diagnostic data are of only auxiliary importance.

In a certain proportion of patients, an increase in the concentration of IgA in the blood is detected, which does not have significant clinical significance.

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Instrumental diagnostics of Bechterew's disease

Among the instrumental methods, radiography of the sacroiliac joints and spine is of primary importance in diagnosing and assessing the progression of AS. X-ray CT and MRI can be prescribed for early diagnostics of sacroiliitis. These methods are also used to determine the condition of the spine when differential diagnostics are necessary, as well as to detail the condition of individual anatomical structures of the spine when the diagnosis of this disease has already been established. When performing CT, in addition to visualization in the axial plane, it is advisable to obtain reconstructed images in the coronary plane. In MRI, it is recommended to use 3 types of signal: T1, T2 and T2 with signal suppression from adipose tissue.

All patients should have regular ECG. If murmurs are detected in the heart area, echocardiography is indicated.

Early diagnosis of Bechterew's disease

The presence of the disease should be suspected in the following clinical situations (mainly in young people).

• Chronic pain in the lower back of an inflammatory nature.
• Persistent monoarthritis or oligoarthritis with predominant damage to large and medium joints of the lower extremities, especially in combination with enthesitis.
• Recurrent anterior uveitis.

Chronic pain in the lower back is usually considered to be of an inflammatory nature if it lasts for at least 3 months and has the following symptoms:

• Accompanied by morning stiffness lasting more than 30 minutes.
• They decrease after exercise and do not weaken at rest.
• Awakening due to pain at night (exclusively in the second half).
• Alternating pain in the buttocks.

In the presence of any two of these signs, the probability of inflammatory spinal lesion (in patients with chronic pain in the lower part of the splint) is 10.8%, in the presence of three or four signs - 39.4%.

The likelihood of a diagnosis of AS in these patients also increases if such manifestations of ankylosing spondylitis as asymmetric arthritis of large and medium joints of the lower extremities, heel pain, dactylitis (sausage-shaped swelling of the finger due to inflammation of the tendons of the toe or hand), anterior uveitis, psoriasis, nonspecific ulcerative colitis are detected during examination or in the anamnesis, as well as upon receipt of information about the presence of AS or other seronegative spondyloarthritis in direct relatives.

Of decisive importance in the diagnosis of Bechterew's disease are the signs of sacroiliitis detected during radiography of the sacroiliac joints. The first radiographic changes characteristic of sacroiliitis are considered to be the loss of continuity (blurring) of the end plate in one or more areas of the joint, individual erosions or areas of widening of the joint space (due to osteitis), as well as strip-like or spotty periarticular osteosclerosis (excessive bone formation in areas of osteitis). The combination of these signs is of diagnostic importance. Almost always the first disorders are noted on the part of the ilium. It should be taken into account that the width of the sacroiliac joint space during radiography in the norm (after the completion of pelvic ossification) is 3-5 mm, and the width of the end plate is no more than 0.6 mm in the second ilium and no more than 0.4 mm in the sacrum.

When sacroiliitis is detected, it is recommended to determine the presence of the so-called modified New York criteria for ankylosing spondylitis

• Clinical criteria.

Pain and stiffness in the lower back (for at least 3 months) that improves with exercise but persists with rest.

Limitations of movement in the lumbar spine in both the sagittal and frontal planes (to assess movements in the sagittal plane, the Wright Schober test is used, and in the frontal plane, lateral torso tilts are used).

Limitations of respiratory excursion of the chest compared to nagels in healthy individuals (depending on age and gender).

• Radiological criterion of sacroiliitis [bilateral (stage II and higher according to the Kellgren classification) or unilateral (stage III-IV according to the Kellgren classification)].

If there is a radiological and at least one clinical criterion, the diagnosis is considered reliable.

It should be taken into account that these criteria are considered indicative and when diagnosing Bechterew's disease, it is necessary to exclude other, similarly occurring diseases. X-ray stages of sacroiliitis according to the Kellgren classification are presented below.

• Stage 0 - no changes.
• Stage I - suspicion of the presence of changes (absence of specific changes).
• Stage II - minimal changes (small, localized areas of erosion or sclerosis in the absence of narrowing of the gap).
• Stage III - unconditional changes: moderate or significant sacroiliitis with erosions, sclerosis, expansion, narrowing or partial ankylosis.
• Stage IV - advanced changes (complete ankylosis).

Radiographic signs of sacroiliitis may appear with a "delay" of 1 year or more. In the early stages of ankylosing spondylitis, especially before the complete closure of the growth buds in the pelvic bones (at the age of 21), difficulties in interpreting the condition of the sacroiliac joints often arise. These difficulties can be overcome with the help of CT. In those cases when there are no radiographic signs of sacroiliitis, but the suspicion of the presence of the disease remains, MRI diagnostics of the sacroiliac joints is indicated (using T1, T2 modes and T2 mode with signal suppression from fat tissue), which reveals signs of edema of various structures of the sacroiliac joints before the development of visible radiographic changes.

In situations where the clinical picture is dominated by symptoms of peripheral arthritis, the same signs, classification criteria and diagnostic methods for sacroiliitis as those listed above are used to diagnose Bechterew's disease. It should be taken into account that typical peripheral arthritis in children and adolescents may not be accompanied by sacroiliitis and spondylitis for many years. In these cases, the determination of HLA-B27 is of additional importance; its detection, although not of absolute diagnostic value, nevertheless indicates a high probability of seronegative spondyloarthritis, including AS. In these cases, the diagnosis is clarified only during subsequent observation of the patient with regular targeted examination.

In patients with recurrent anterior uveitis, in the absence of signs of ankylosing spondylitis and other seronegative spondyloarthroses during targeted examination, determination of HLA-B27 is indicated. If this antigen is detected, further observation of the patient by a rheumatologist is indicated (although isolated HLA-B27-associated uveitis is possible), and the absence of HLA-B27 is considered a sign of the etiology of uveitis.

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Bechterew's disease: differential diagnosis

In children and adolescents, pain in the spine and movement disorders in it, similar to those in AS, are noted in Scheuermann-Mau disease (juvenile kyphosis), osteoporosis, and severe juvenile osteochondrosis of the spine. In these diseases, characteristic radiographic changes in the spine are detected, confirmed by osteodensitometry in the case of osteoporosis. When conducting differential diagnostics, two circumstances should be taken into account.

1. In childhood, the disease often begins not with damage to the spinal column, but with peripheral arthritis and/or enthesitis. Spondylitis usually joins only after the age of 16, i.e. AS is a rare cause of isolated pain in the spine in children.
2. In patients with a confirmed disease, radiographic changes in the spine are often detected, characteristic of Scheuermann-Mau disease (anterior wedge-shaped deformity, Schmorl's nodes), which can be an additional cause of pain and movement limitations.

Differential diagnostics of Bechterew's disease is carried out with infectious spondylodiscitis. Radiological manifestations of spondylodiscitis of infectious and non-infectious (for example, with AS) genesis in the early stages may be similar: rapid development of destruction of the bodies of adjacent vertebrae and a decrease in the height of the intervertebral disc located between them. The main differential diagnostic value is a tomographic study (mainly MRI), which can detect the formation of "stool deposits" in the paravertebral soft tissues, which is typical of spinal infections. Also important are measures to identify the entry "gates" of tuberculosis or other bacterial infections. Among chronic infections that occur with damage to the musculoskeletal system, brucellosis should be singled out. This disease causes spondylitis, arthritis of large peripheral joints and often sacroiliitis (usually unilateral), which can be the cause of erroneous diagnosis of Bechterew's disease. In most cases, brucellosis spondylitis and arthritis are caused by hematogenous spread of infection with the development of spondylodiscitis. High cytosis and neutrophilia in the cerebrospinal fluid are noted. An increase in body temperature is typical. The diagnosis is established on the basis of laboratory tests (serological reactions).

Individual clinical and radiographic manifestations of the spine, similar to the symptoms of AS, are possible in Forestier's disease (idiopathic diffuse hyperostosis of the skeleton), acromegaly, axial osteomalacia, fluorosis, congenital or acquired kyphoscoliosis, pyrophosphate arthropathy, ochronosis. In all these cases, the criteria for AS are not noted, and the radiographic changes, as a rule, only resemble the changes that occur in AS, but are not identical to them.

X-ray picture of sacroiliitis is found in various diseases, including rheumatic ones, such as RA (usually in the late stages of the disease), gout, SLE, BD, sarcoidosis and other diseases, as well as in the case of inspection damage to these joints. X-ray changes resembling sacroiliitis are possible in osteoarthrosis of the sacroiliac joints, pyrophosphate arthropathy, condensing ileitis, Paget's disease of bone, hyperparathyroidism, osteomalacia, renal osteodystrophy, polyvinyl chloride and fluoride intoxication. In paraplegia of any genesis, ankylosis of the sacroiliac joints develops.

Bechterew's disease diagnostics allows to classify this disease into the group of seronegative spondyloarthritis, which also includes reactive arthritis, psoriatic arthritis, spondylitis in nonspecific ulcerative colitis and undifferentiated spondyloarthritis. All these diseases are characterized by common clinical and radiological manifestations. Unlike other seronegative spondyloarthritis, AS is characterized by persistent and progressive inflammation of the spine, prevailing over other symptoms of ankylosing spondylitis. However, any other seronegative spondyloarthritis can sometimes proceed in a similar way, and in such cases, ankylosing spondylitis is considered to be one of the manifestations of these diseases.

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