After conducting an oral interview with the patient, the doctor will conduct several studies to find out exactly which condition is present.
Interview with the patient: During the interview, the patient will explain the symptoms related to muscle weakness. Besides, the conditions of other body areas such as skin, heart, lungs and joints might be also reviewed so that examinations on these and other systems can be conducted. The doctor will measure the strength of the muscles closest to the trunk of the body, the abnormal elevation of muscles enzymes, the electromyograph (EMG) and magnetic resonance imaging (MRI) findings and if specific abnormalities detected with muscle biopsy are present.
Blood testings: The results of blood test help the doctor to find out if there are conditions of muscle damage by taking a look at the enzymes. Specifically, the tests reveal the presence of abnormally high levels of muscle enzymes, CPK or creatinine phosphokinase, aldolase, SGOT, SGPT, and LDH. If the muscle is damaged by inflammation, these enzymes are released into the blood. These enzymes can also be used as a measure of the activity of the inflammation. Second, blood in combination with urine tests help to reveal if internal organs became abnormal. In order to get a clear picture, some other tests may be considered such as chest X-rays, mammograms, PAP smears and other screening tests. Third, blood tests reveal the presence of Autoantibodies (antinuclear antibodies and myositis specific antibodies such as Jo-1 antibody) which are a sign of polymyositis.
Electromyograph (EMG) and nerve conduction velocity: These are electrical tests of muscle and nerves that help showing abnormal findings belonging to polymyositis. Further, they help excluding other nerve-muscle diseases. The test is conducted by inserting a thin needle electrode through the skin into the muscle. Electrical activity is measured as the muscle is being relaxed or tightened. In this way, the presence of a muscle disease is confirmed by finding changes in the pattern of electrical activity. The doctor can determine the distribution of the disease by testing different muscles.
MRI scanning: An MRI is a type of radiology test, which creates scanned images of the muscles in a cross-sectional way using a powerful magnetic field and radio waves. This test is very useful since it can assess inflammation over a large area of muscles.
Muscle biopsy: During this test a small piece of muscle tissue is surgically removed and analysed in a laboratory. In general the muscle sample is taken from the quadriceps muscle of the front of the thigh, the biceps muscle of the arm, and the deltoid muscle of the shoulder. The results show if the muscle is inflamed, damaged or if there is a deficiency of certain proteins or enzymes.