Determining the Existence of Tissue Damage with the LDH Blood Test
written by: Leigh A. Zaykoski•edited by: Leigh A. Zaykoski•updated: 4/30/2009
The LDH blood test is one of the lab tests doctors use to determine if muscle damage is present. If damage is detected, this test can also help doctors determine its severity.
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Laboratory tests are used as tools to help doctors and other medical professionals determine what is causing medical symptoms or decide if a treatment has been working properly. Blood tests can also be used to build a picture of the quality of someone's general health. One of the blood tests used by doctors is the LDH blood test. Also known as the LD, LDH isoenzymes, and lactate dehydrogenase test, this test can be ordered to diagnose or monitor progressive conditions.
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Why the Test is Ordered
If a patient exhibits signs or symptoms of having cellular or tissue damage, a total LDH level may be ordered. If this level is abnormally high, LDH isoenzyme levels may be tested along with ALT, AST, and ALP tests. These tests can help doctors determine where the damage is located and how severe the problem has become. Another reason to test LDH levels is to monitor the damage caused by injury to the muscles or to diagnose someone with hemolytic anemia. This type of anemia is caused by the destruction of red blood cells, which can elevate LDH levels. In the past, LDH levels were ordered with cardiac enzyme tests when a patient was suspected of having a heart attack. This test has been replaced with the troponin test, which can more accurately identify damage to the heart tissues.
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LDH Blood Test Results
If LDH levels or the ratio of LDH enzymes in the blood are elevated, this can indicate tissue damage somewhere in the body. These levels typically rise once damage has begun, peak after some tissue damage, and then drop at a later time. For example, someone who has had a myocardial infarction will show rising levels within 24 hours, peak levels within 3 days, and normal levels 10 to 14 days after the cardiac event. LDH levels may be elevated due to several conditions as well as some over-the-counter and prescription medications. Medical conditions that can cause elevated LDH levels include stroke, pernicious anemia, mononucleosis, liver disease, pancreatitis, lymphoma, kidney disease, and muscular dystrophy. Aspirin, pain medications, alcohol, and anesthetic agents can also cause elevated LDH blood test results. Low levels of LDH are usually of no concern and can sometimes occur when someone takes a large amount of Vitamin C on a regular basis.
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Inaccurate Test Results
Some factors can alter your LDH levels, making the test results unreliable. If you have exercised strenuously before completing the test, your LDH levels may be elevated for a short period. If your blood specimen is not handled properly, the sample may become hemolyzed. This can occur if the sample is dropped, stored incorrectly, or left in extreme hot or cold temperatures. If you have a high platelet count, this will increase your LDH level artificially.
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Lab Tests Online. "LDH: The Test." Retrieved 30 April 2009. Available: LDH: The Test