As PMR is a diagnosis of exclusion, patients may have to through extensive workup to rule out other conditions before receiving the diagnosis. If a patient reports symptoms characteristic of PMR, a physician will review the medical history and perform a physical examination. Among the signs that the physician looks for is a decrease in the active range of motion in the neck, shoulders and hips. The physician may also check for muscle tenderness, but this is not a prominent feature of PMR. When it does occur, the tenderness is usually due to inflammation. The diagnostic procedure for PMR may be lengthier in patients who do not exhibit characteristic symptoms or presentations (e.g., patients younger than 50).

Laboratory and clinical tests follow the physical examination. Although no single test can be used to positively identify PMR, findings of multiple tests help to rule out other conditions that may be causing the signs and symptoms displayed. Tests that may be performed include:

• Blood tests. A number of tests may be used to detect abnormal levels of blood chemicals. In PMR:
  
  
• • Sed rates are elevated.
    
    
  • A C-reactive protein test reveals high levels of C-reactive protein (produced by the liver in response to injury or infection).
    
    
  • An enzyme test reveals high levels of liver enzymes and normal levels of creatine kinase (a muscle enzyme).
    
    
  • A complete blood count reveals high levels of platelets due to inflammation and low levels of red blood cells indicating mild anemia.
    
    
  • Serologic tests (such as an ANA test for antinuclear antibodies) are negative.
    
    
  • Rheumatoid factor (RF) tests are negative.
    
    
• Biopsies. Small tissue samples are removed for laboratory examination. Results are usually normal in PMR, but biopsies may be used to detect the presence of other conditions. Muscle biopsies reveal no damage that may cause the characteristic pain and stiffness. Temporal artery biopsy may be used to detect the presence of temporal arteritis, a condition that causes arteries, particularly those in the head, to swell.

Imaging tests may also be used to assist in ruling out other conditions. However, most physicians employ imaging tests only if the diagnosis remains uncertain. Tests that may be performed include:

• MRI (magnetic resonance imaging). Uses powerful magnets to produce images of internal structures. An MRI may confirm inflammation in the more distant joints (such as hands or feet) that is not restricted to the synovium.
  
  
• Ultrasound. Uses sound waves to create images of internal tissues. Ultrasound may reveal effusions (accumulation of fluid) in the shoulder. There is good correlation of results between ultrasound and MRI, so in most cases only one is used. Cost considerations typically favor ultrasound, but many physicians prefer MRI.
  
  
• X-ray. Images are produced using low doses of radiation. X-rays may be routine tests on inflamed joints. These rarely reveal any abnormalities in PMR.
  
  
• Electromyograms. Graphic records of electrical activity in the muscle. These show no abnormalities.

Many conditions mimic the symptoms of PMR and may explain the findings. The presence of another disease excludes a diagnosis of PMR. For an accurate diagnosis of PMR, these conditions are usually excluded:

• Rheumatoid arthritis. A type of chronic inflammation that may disfigure joints. There may be some overlap between PMR and rheumatoid arthritis, particularly due to the age of the patients involved. However, rheumatoid arthritis is only partially responsive to low doses of corticosteroids. Fewer joints are swollen in PMR, and the swelling subsides completely with low doses of corticosteroids. Also, RF tests are positive in rheumatoid arthritis and negative in PMR. In the instances where patients have both rheumatoid arthritis and PMR, the two conditions will be treated separately.
  
  
• Hypothyroidism. Insufficient thyroid function. Some instances of this condition may result in swelling suggestive of PMR. Certain characteristics of hypothyroidism are not seen in PMR, such as the slow relaxation of deep tendon reflexes, low concentrations of an amino acid called tyrosine (T4) and high serum concentrations of a hormone called thyrotropin (also called thyroid-stimulating hormone, TSH).
  
  
• Infective endocarditis. Inflammation of the membrane surrounding the heart due to infection. A persistent fever accompanying the criteria for PMR may suggest infective endocarditis. Physicians may check for heart murmur, positive blood cultures and growth of bacteria on a heart valve (using echocardiogram).
  
  
• Fibromyalgia. A chronic condition involving widespread musculoskeletal pain. Many instances of fibromyalgia pain are similar to the pain associated with PMR. Most fibromyalgia patients are under age 50. Physical examination reveals no obvious abnormalities. Sed rate is normal.
  
  
• Cancer. There is no association between PMR and cancer, but malignancy can mimic the diffuse (scattered) muscle and joint pains of PMR. Cancer pain will not resolve with the use of corticosteroids.
  
  
• Polymyositis. Muscle inflammation and weakness. Proximal muscle weakness (in and around the torso) is associated with polymyositis, but prominent shoulder and/or hip pain is not. Diagnosis of this condition may be established by elevated muscle enzymes (e.g., creatine kinase), abnormal electromyogram and evidence of myositis (muscle swelling) on muscle biopsy.
  
  
• Bursitis or tendinitis. Inflammation of the bursae (fluid-filled cavities between tendons and bones) or tendons. PMR symptoms in the shoulders may be similar to those of bursitis or tendinitis. However, tenderness is minimal in most cases of PMR. Bursitis and tendinitis do not tend to affect both shoulders and there is no elevated sed rate. Some researchers, however, believe that a form of bursitis may be involved in the stiffness of the shoulders in PMR.

Certain disorders may coexist with PMR. A physician will usually test for:

• Temporal arteritis (also known as giant cell arteritis). A chronic disorder that results in the swelling of the arteries of the head, neck and arms. The temporal arteries, located on the temples on each side of the head, are most commonly affected. The exact nature of the relationship between temporal arteritis and PMR is not understood, but some evidence suggests that the conditions may represent a single disease spectrum. Both conditions affect the same demographic (white, over age 50) more often than others.
  
  Symptoms of temporal arteritis that do not occur with PMR alone include headache, jaw pain, loss of vision and tenderness of the temporal arteries. Because of potentially serious complications of temporal arteritis, which can include blindness and stroke, physicians may actively monitor PMR patients for signs of the disease. According to the National Institutes of Health, about 15 percent of PMR patients also develop temporal arteritis, either at onset or after PMR symptoms disappear. If temporal arteritis is suspected, testing should include an eye exam. Treatment of temporal arteritis should be started earlier to prevent serious complications.
  
  Corticosteroids are very effective in the treatment of both of these conditions, but temporal arteritis requires a higher dose. To determine the presence of temporal arteritis, a biopsy on a blood vessel in the scalp is usually performed. A small piece of the artery is removed and examined under a microscope.
  
  
• Remitting seronegative symmetrical synovitis with pitting edema syndrome (RS3PE). Typically marked by a sudden onset of arthritis in patients who are frequently over age 50 and do not possess factors of rheumatoid arthritis. The signs and symptoms of RS3PE are frequently mistaken for those of PMR. RS3PE generally responds well to corticosteroids, the predominant drugs used in the treatment of PMR. Some physicians consider this a variant of PMR with prominent edema.