If your doctor suspects you have polymyositis, he or she might suggest some of the following tests:
June 24, 2014
- Blood tests. A blood test will let your doctor know if you have elevated levels of muscle enzymes, such as creatine kinase (CK) and aldolase. Increased CK and aldolase levels can indicate muscle damage. A blood test can also detect specific autoantibodies associated with different symptoms of polymyositis, which can help in determining the best medication and treatment.
- Electromyography. A doctor with specialized training inserts a thin needle electrode through the skin into the muscle to be tested. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles.
- Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle.
- Muscle biopsy. A small piece of muscle tissue is removed surgically for laboratory analysis. A muscle biopsy may reveal abnormalities in your muscles, such as inflammation, damage or infection. The tissue sample can also be examined for the presence of abnormal proteins and checked for enzyme deficiencies. In polymyositis, a muscle biopsy typically shows inflammation, dead muscle cells (necrosis), and degeneration and regeneration of muscle fibers.
- NINDS polymyositis information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/polymyositis/polymyositis.htm. Accessed April 11, 2014.
- Goldman L, et al. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.clinicalkey.com. Accessed March 25, 2014.
- Imboden JB, et al. Current Rheumatology Diagnosis & Treatment. 3rd ed. New York, N.Y.: The McGraw-Hill Companies; 2013. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=809. Accessed March 25, 2014.
- Oddis CV, et al. Rituximab in the treatment of refractory adult and juvenile dermatomyositis and adult polymyositis: A randomized, placebo-phase trial. Arthritis and Rheumatology. 2013;65:314.
- Miller ML. Diagnosis and differential diagnosis of dermatomyositis and polymyositis in adults. http://www.uptodate.com/home. Accessed March 25, 2014.
- Miller ML, et al. Initial treatment of dermatomyositis and polymyositis in adults. http://www.uptodate.com/home. Accessed March 27, 2014.
- Miller ML, et al. Treatment of recurrent and resistant dermatomyositis and polymyositis in adults. http://www.uptodate.com/home. Accessed March 27, 2014.