Serum LDH

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

To help identify the cause and location of tissue damage in the body, and to monitor its progress. LDH is elevated in a wide variety of conditions reflecting its wide spread tissue distribution. Historically, has been used to help diagnose and monitor a heart attack, but troponin has replaced LDH in this role.

When this test is required

A total LDH level may be used with other tests, as a screening test when your doctor suspects some kind of cellular or tissue damage. If the total LDH is elevated, then the doctor may request LDH isoenzymes, or more commonly other tests such as ALT, AST or ALP to help diagnose the condition and to help determine which organs are involved. Once the acute or chronic problem is diagnosed, total LDH levels may be used at regular intervals to monitor its progress and/or resolution.LDH levels may also occasionally be used to monitor damage caused by muscle trauma or injury and to help identify haemolytic anaemia (anaemia caused by the breakdown of red blood cells – either because the cells are unusually fragile or because something is mechanically damaging them, such as an artificial heart valve).When a patient has symptoms of a heart attack, troponin levels are used instead of LDH.

What the Test Detects

Lactate dehydrogenase (LDH, or LD) is an enzyme found in almost all body tissues. Usually the concentration of LDH in the blood is low, because it usually stays contained within the tissues’ cells. When cells are damaged or destroyed, however, they release LDH into the bloodstream, causing blood levels to rise. For this reason, LDH is used as a general marker of injury to cells; it is not useful for determining which…Lactate dehydrogenase (LDH, or LD) is an enzyme found in almost all body tissues. Usually the concentration of LDH in the blood is low, because it usually stays contained within the tissues’ cells. When cells are damaged or destroyed, however, they release LDH into the bloodstream, causing blood levels to rise. For this reason, LDH is used as a general marker of injury to cells; it is not useful for determining which specific cells are damaged. Elevations of LDH may be measured either as a total LDH or as LDH isoenzymes. Isoenzymes are slightly different molecular versions of the same enzyme. A total LDH level is an overall measurement of five different LDH isoenzymes. A high total LDH level reflects tissue damage but it is not specific to any one type of tissue, and so, by itself, it cannot be used to identify the underlying cause or its location. Although there is some overlap, each of the five LDH isoenzymes tends to be concentrated in specific body tissues. Because of this, measurements of the individual LDH isoenzyme levels can be used, along with other tests, to help determine the disease or condition causing cellular damage and to help identify the organs and tissues involved. In general, the isoenzyme locations tend to be:LDH-1 – heart, red cells, kidney, germ cells LDH-2 – heart, red blood cells, kidney (lesser amounts than LDH-1) LDH-3 – lungs and other tissues LDH-4 – white blood cells, lymph nodes; muscle, liver (smaller amounts than LDH-5) LDH-5 – liver, muscle While all of the isoenzymes are represented in the total LDH, LDH-2 usually makes up the greatest percentage. See MoreSee Less

Preparation for the Test

None

Sample Requirements

A blood sample taken from a vein in your arm

Additional Notes

Many things can affect LDH results that are not necessarily a cause for concern. For example: Strenuous exercise can cause temporary elevations in LDH. Haemolysis of the blood specimen can cause false positives (“haemolysis of blood” refers to breakage of red blood cells in the blood sample which may happen if the specimen is handled roughly, stored in extreme temperatures or if the specimen was difficult to collect). If your platelet count is increased, serum LDH will be artificially high and not reflective of the LDH actually present.

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