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Rheumatoid arthritis (RA) can be a difficult disease to diagnose because it often begins gradually and only a few symptoms may be present in the early stages. Compounding the problem is that many diseases, including other types of arthritis and joint conditions, behave in a similar manner.

The following overview demonstrates how many conditions mimic aspects of rheumatoid arthritis. Understanding their differences helps doctors and patients make educated decisions about diagnosis, treatment and other aspects of disease management.

Ankylosing spondylitis is a type of arthritis that affects the spine. It may cause pain and stiffness from the neck down to the lower back.
Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm into the hand, becomes pinched from swelling of the nerve, tendons or both. The symptoms, which usually start gradually, include tingling or itching and numbness in the palm of the hand and the fingers, especially the thumb, index and middle fingers.
Fibromyalgia is characterized by aching and pain in muscles, tendons and joints all over the body, but especially along the spine. The body is also sensitive to pressure in specific areas. These are called trigger points.
Polymyalgia rheumatica is a rare, inflammatory condition that causes pain or aching in the large muscle groups, especially around the shoulders and hips.
Systemic lupus erythematosus (SLE) is an immune disorder that may cause extreme fatigue and painful or swollen joints. It is identified by the presence of a characteristic rash, often brought on by sun-sensitivity, hair loss and abnormalities in multiple organ systems.
Bursitis and tendonitis, also known as soft tissue rheumatic syndromes, are associated with pain, swelling or inflammation in the tendons, ligaments and muscles around a joint. Because these structures are near joints, the pain in these areas may be mistaken for arthritis. However, arthritis includes inflammation inside the actual joint, not just around it.
Tennis elbow, trigger finger and impingement syndrome, which often cause pain in the shoulders and extremities of older adults, are overuse injuries and are commonly mistaken for arthritis.

Differentiating the Signs of Rheumatoid Arthritis
Several types of arthritis are characterized by stiffness of the joints and joint pain, but rheumatoid arthritis is set apart by a few distinguishing features. One is the presence of morning stiffness. It is most pronounced in the morning because fluid in and around the joints redistributes during sleep.

Other inflammatory conditions, including polymyalgia rheumatica and ankylosing spondylitis, can also be accompanied by stiffness. But unlike rheumatoid arthritis, the stiffness is usually relieved by rest and is typically worse after activity or in the afternoon.

Sometimes it is the presence of swelling and inflammation in particular joints that differentiates rheumatoid arthritis from other diseases. For example, osteoarthritis, one of the most common forms of arthritis, usually spares the wrist and what are known as the metacarpophalangeal (MCP) joints, such as the knuckles. Rheumatoid arthritis, on the other hand, is more likely to occur in these joints.

Doctors distinguish rheumatoid arthritis from rheumatic fever because the latter is more likely to be migratory in nature. That simply means the arthritic pain moves from one joint to another.

Gout is frequently confused with rheumatoid arthritis, and it is common for the lumps associated with it to be mistaken for rheumatoid nodules. However, gout usually affects a single joint and can be diagnosed with a test that determines whether crystals are present in the joint fluid.

Chronic Lyme disease also typically involves only one joint, most commonly the knee. It can be ruled out by the presence of a characteristic rash and blood tests.

Arthritis due to bacterial infection, also known as pyogenic arthritis, can be ruled out because it is distinguished by the presence of chills, fever and a test that identifies a specific organism in the joint fluid that causes the infection.

Making a Diagnosis
Because so many diseases are similar, it is important to seek care from a physician who is equipped to make the right diagnosis. That ensures patients avoid unnecessary testing, drug therapy and costs. It also speeds up the process of starting effective treatment, which can stop or slow the progression of long term joint damage.

Since there is no definitive test to positively pinpoint rheumatoid arthritis, the process of diagnosing the disease involves several steps. They include a complete medical history, a comprehensive review of the symptoms, a physical examination, during which physicians look for signs characteristic of the disease, lab tests and X-rays.

Laboratory Tests
Several laboratory tests may be employed to uncover abnormalities that are commonly found in rheumatoid arthritis. Doctors are looking for:

Rheumatoid factor, an antibody that is eventually found in approximately 80 percent of patients with rheumatoid arthritis. Its presence has been correlated with aggressive and erosive disease. It is not a clear cut indicator of disease since as few as 30 percent of patients may have rheumatoid factor in the early stages. Some people test positive for rheumatoid factor, yet never develop the disease.
Citrulline antibody (also referred to as anti-citrulline antibody, anti-cyclic citrullinated peptide antibody and anti-CCP) is present in most patients with rheumatoid arthritis. Its presence is useful in diagnosing rheumatoid arthritis in patients who have unexplained joint inflammation and when rheumatoid factor is not present. In these situations, researchers believe the presence of citrulline antibodies may represent the earlier stages of rheumatoid arthritis.
Antinuclear antibody (ANA) may also be present in patients with rheumatoid arthritis, but it is more commonly associated with other rheumatoid diseases such as lupus.
Erythrocyte sedimentation rate (ESR) or “sed rate” is generally high in people with rheumatoid arthritis. It indicates the presence of an inflammatory process in the body. People with rheumatoid arthritis tend to have elevated ESRs, while people who have other arthritic conditions, such as osteoarthritis, tend to have normal ESRs.
C-reactive protein is another useful measurement of disease activity.

X- rays
Physicians frequently use X-rays to determine the degree of joint destruction, but they are not useful in the early stages of rheumatoid arthritis before bone damage is evident. They can be used to set a baseline, however, and to monitor disease progression in later stages.

Early Treatment is Important
When left untreated or inadequately managed, rheumatoid arthritis patients have been shown to experience increased disability and a somewhat shorter life span as compared to the normal population. The joint damage is persistent and progressive, especially in the first two years of disease. That is why diagnosing the disease and starting treatment at the earliest possible stage is so important.

Research has demonstrated that aggressive, effective treatment significantly reduces the progression of rheumatoid arthritis. Studies have also shown that people who receive early treatment feel better, are more likely to lead an active life and are less likely to experience the type of joint damage that can eventually lead to joint replacement.