How is Rheumatoid Arthritis (RA) Diagnosed, Evaluted & Monitored

by Dr. Arvind Chopra

The diagnosis of rheumatoid arthritis (RA) is essentially clinical. A typical picture is that of a woman who is near menopause and develops slowly progressive pain and swelling in small joints of the hands and feet with feeling of stiffness and slowness of body movement( especially in the joints) on awakening in the morning. Other joints that are commonly affected are knees, wrists, shoulders,elbows and ankles. The pattern of joint affection is usually symmetrical. Though neck pain and stiffness often accompanies arthritis, back ache is not a feature of RA. When chronic and progressive, the patients often develop deformities of the joints,especially those of hands and feet. RA is predominantly a woman's disease but men also suffer from severe RA and no age is exempt. Uncommonly, the patient complains of small firm nodules (marble size) under the skin near elbows or over hands and feet. It is this kind of a clinical picture that should ring the first bell to announce the disease.

Thus the doctor ought to carefully review the patient's narration of symptoms and examine the joints for features of inflammation and deformity. The clinical examination must include all systems like cardiovascular, pulmonary and nervous system. Certain blood and X-ray tests are often required. An early disease is often a challenge and several visits may be necessary before the doctor can be certain of the diagnosis. As an important guidance, patients suffering from multiple joint pain and swelling (called polyarthritis) need to be carefully observed for 6 weeks or so following the onset of disease before making a definite diagnosis of RA. Several viruses (such as respiratory illness, mumps, and hepatitis) can cause a RA like polyarthritis that completely subsides within 6 weeks or so.

Blood is often tested for erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to measure the extent of disease activity and progression. Routine blood testing may also reveal anemia (low hemoglobin) which can be due to either nutrition deficiency (especially iron and folic acid) and/or severe RA (effects bone marrow). Several other routine blood tests are ordered to evaluate blood sugar, liver and kidney functions, and lipids (cholesterol) which are relevant to assessing the patient's general health and look for any other occult disease complication. It is prudent to add that patients of RA are prone to hyperlipidemia (increased cholesterol) related thickening of blood vessel walls (atherosclerosis) and attendant cardiac and other circulatory complications (ischemic heart disease, strokes). The blood tests are also required to assess the patient's fitness for medications [ in particular potent anti-rheumatoid drugs like methotrexate, leflunomide, sulfasalazine and the newer biologic agents (such as rituximab, infliximab and tocilizumab]. It is prudent to remember that though RA is predominantly an arthritis, it is actually a systemic disorder that can also uncommonly affect other body systems such as lungs and nerves.

Rheumatoid factor (RF) antibody and cyclic citrulline peptides antibody (anti-CCP antibody) are often present (over 70%) in blood/serum of RA patients. Presence of RF and anti-CCP strengthen the diagnosis. RF is generally the preferred test and can be easily carried out in all laboratories. Anti-CCP is a more expensive test but provides a stronger diagnostic clue especially when the clinical picture is not typical. Certain other antibodies like ANA (antinuclear antibody) are also tested to screen other related complex rheumatic disorders. ANA can be infrequently positive in patients with RA but in an atypical clinical situation would need to be followed by more specific blood antibody tests ( such as antids DNA and anti nuclear RNP) to exclude complex rheumatic disorders (like lupus and mixed connective tissue disease). It must be borne in mind that several antibodies like RF and ANA are also present to a limited extent (under 10%) in normal healthy people and several other systemic disorders. These antibodies ought to be tested with care and expertise in standardized labs. Often the techniques are complex. While reporting these antibodies, labs must indicate their quantitative values, type of method used and controls. Finally, none of these antibodies are a substitute for a good clinical evaluation of RA by a competent doctor. Do not rush into making a diagnosis based only on the presence of these antibodies. A clinical correlation is mandatory. Though there are few genetic tests that indicate susceptibility and severity of RA (such as HLA DR typing), they have not been found useful in routine clinical practice. Also, genetics may differ in different ethnic populations.

One need not test synovial fluid from a joint to diagnose RA but the same is useful to exclude infections (in particular tuberculosis in our country). On similar grounds, arthroscopy (a surgical procedure used to examine joint and perform some limited surgery) is not required to diagnose RA but can be a useful tool to carry out a synovial tissue biopsy in rare instances of a difficult to diagnose chronic affection of a single large joint (usually knee).What is the role of X-Rays? One need not take an X-Ray of every painful joint. Radiological changes of significance often take time to show. Initially, an X-Ray may only show soft tissue swelling of a joint which can be anyway appreciated better by the eye, and further evaluated on clinical examination. However, X-Rays of hands and wrists are important in RA and may begin to show changes consistent with the diagnosis as early as 6-8 weeks after the onset of the disease. A critical finding in the X-Ray is that of early joint damage which is often reported as 'erosion' near the joint margin. Erosive arthritis is always a serious finding because it invariably means a severe disease which is likely to be progressive and lead towards early joint deformities. A normal XRay of a painful joint does not exclude the possibility of RA. X-rays can also be helpful in monitoring the progression of disease and joint damage over time. X-Rays would also be required when surgical correction is being considered. In atypical clinical situations, usually marked by affection of fewer large joint (usually lower limb) involvement and back aches, X-Rays of the spine and pelvis are often taken to exclude inflammatory disorders of the spine/axial skeleton (such as ankylosing spondylitis).

There are several other radiology imaging modalities which are infrequently indicated and required but can be crucial to diagnosis (including that of RA complications) in certain difficult clinical situations. Sometimes when a patient continues to suffer from joint aches and pains without showing any clear cut clinical evidence, a radioactive bone scan can show evidence and extent of arthritis which helps in the overall diagnosis. MRI and CT scan can show great anatomical detail of an affected joint especially with reference to complications and need for surgery. MRI scan is of outstanding value with regards to diagnosing chronic back ache and other disorders of spine and sacroiliac joint (hall mark of ankylosing spondylitis like disorders). Osteoporosis (thinning of bones) is an important accompaniment and or complication of RA which can be due to age,menopause, poor physical activity and drugs (especially steroids). Bone mineral density (BMD) is measured by DEXA (a radiology imaging machine somewhat similar to CT scan) to diagnose osteoporosis. Newer techniques in ultrasonography are now being made available to quickly diagnose early arthritis and joint damage in RA and other inflammatory disorders.

In conclusion, the diagnosis of RA needs much care, attention and expertise from the doctor. A wrong diagnosis, which is not too infrequently seen in my referral practice, leads to unfortunate psychological stress and avoidable finance losses. Every investigation carried out must be supported by good clinical reasoning and interpreted in a clinical context. RA is a lifelong disease which requires careful selection of several drugs to treat and regular supervised medical care and monitoring. Therapy often requires changes. Sometimes, the disease is progressive despite optimum therapy. All this would mean, that patients of RA need repeated investigations to ensure good control of disease and timely detection of complications. Patients must try and understand the logic and reasoning of carrying out the investigations required to make a proper diagnosis of RA. And it is equally important, that doctors make themselves responsible to explain to the patients as to why so many investigations are required? Effective management, which includes diagnosis and treatment, of RA actually begins when the patient first steps into the doctor's room. Diagnosis is never a one point event. It is actually a continuous process of confirmation, monitoring and fine tuning so as to relieve the patient of the suffering. RA is no exception.