Lactate Dehydrogenase: Definition, Mechanism, Analysis and Meaning of Results

Also known as LD or LDH, it is an enzyme involved in energy production that is found in almost every cell in the body.

It has its highest levels in the cells of the heart, liver, muscles, kidneys, lungs and blood cells.

Bacteria also produce LD. This test measures the level of LD in blood or other body fluids.

LD and sangre

Usually only a small amount of LD is detected in the liquid portion of the blood (serum or plasma). LD is released from cells into serum when cells are damaged or destroyed.

Therefore, an LD blood level is a non-specific marker for the presence of tissue damage somewhere in the body.

On its own, it cannot be used to identify the underlying cause or location of cell damage . However, it can be used, in conjunction with other blood tests, to help evaluate and / or monitor conditions that lead to tissue damage, such as liver or blood disease or cancer.

net LD

Sometimes when there is an injury, inflammation, or infection within a specific area of ​​the body, such as the brain, heart, or lungs, the fluid builds up or the components of the fluid present change.

The level of LD present in the fluid can be helpful in determining the cause. For example, LD is typically high in cerebrospinal fluid when an individual has bacterial meningitis.

The LD test can also be used, in conjunction with other tests, to determine whether fluid build-up, for example around the heart or lungs or in the abdominal cavity, is due to injury or inflammation (exudate) or due to an imbalance of the pressure of the fluid within blood vessels and the level of protein in the blood (transudate).

Common questions about LD testing

How is the test used?

A lactate dehydrogenase (LD or LDH) test is a non-specific test that can be used in the evaluation of a number of diseases and conditions.

An LD blood test can be used:

  • As a general indicator of the existence and severity of acute or chronic tissue damage.
  • To detect and monitor progressive conditions such as anemia, including hemolytic anemia and megaloblastic anemia, or severe infections.
  • To help stage, determine prognosis, and / or monitor treatment (i.e. chemotherapy) for cancers, such as germ cell tumors (eg, some types of testicular and ovarian cancer), lymphoma, leukemia, melanoma and neuroblastoma.

An LD test is done on body fluids for different reasons:

  • To help evaluate cerebrospinal fluid and distinguish between bacterial and viral meningitis.
  • Assess other body fluids such as pleural, peritoneal, or pericardial fluid and help determine whether the fluid build-up is due to injury and inflammation (exudate) or due to an imbalance of pressure within the blood vessels and the amount of protein in the blood (transudate) This information is useful to guide treatment.

When is it ordered?

Blood test

An LD level, along with other tests, such as a complete metabolic panel (CMP), may be ordered when a health professional suspects that a disease or condition is causing some degree of cell or tissue damage.

If LD is elevated, more specific tests, such as ALT, AST, or ALP, can help diagnose the condition and help determine which organs are involved.

Once the acute or chronic problem is diagnosed, total LD ​​levels can be ordered at regular intervals to monitor its progress and / or resolution.

LD levels can also occasionally be ordered when an individual has experienced muscle trauma or injury or when a person has signs and symptoms of hemolytic anemia.

LD tests can be ordered regularly when a person has been diagnosed with cancer.

Body fluid test

This test may be ordered, for example, when a person has signs and symptoms of meningitis or when someone has a buildup of fluid around the heart, lungs, or abdomen.

What does the test result mean?

Blood test

Elevated levels of LD generally indicate some type of tissue damage. LD levels will generally rise when cell destruction begins, peak after a period of time, and then begin to drop.

LD levels are elevated in a wide variety of conditions, reflecting its generalized tissue distribution.

An elevated level of LD can be observed with:

  • Hemolytic anemia .
  • Pernicious anemia (megaloblastic anemia).
  • Infections such as infectious mononucleosis (mono), meningitis, encephalitis, HIV.
  • Septicemia.
  • Intestinal, myocardial (heart) and lung (pulmonary) infarction.
  • Acute kidney disease
  • Acute liver disease.
  • Acute muscle injury.
  • Pancreatitis.
  • Bone fractures
  • Testicular cancer, lymphoma, or other types of cancer.
  • Severe shock
  • Lack of oxygen ( hypoxia )

A high LD in the blood may indicate that cancer treatment (eg, chemotherapy) has not been successful. A high level is predictive of a poorer survival outlook for people with cancer.

With some chronic and progressive conditions, moderately elevated blood levels of LD may persist.

Low and normal LD ​​levels generally do not indicate a problem. Low levels are sometimes seen when someone ingests large amounts of ascorbic acid (vitamin C).

Body fluids:

Cerebrospinal fluid : A high LD indicates that meningitis is likely caused by bacteria, while a low or normal level indicates that viral meningitis is more likely.

A high LD indicates that the pericardial fluid, peritoneal or pleural fluid is an exudate, while a low level indicates that it is transudate. Transudates are usually caused by congestive heart failure or cirrhosis.

Exudates have several possible causes and generally require additional tests to determine the cause.

Is there anything else I need to know?

Many things can affect LD results that are not necessarily a cause for concern. For instance:

Strenuous exercise can cause temporary elevations in LD.

Hemolysis of the blood sample can cause falsely elevated results. This can happen if the specimen is roughly handled, stored in extreme temperatures, or if the sample was difficult to collect.

If a person’s platelet count rises, the serum LD may be artificially high and not reflect the LD actually present in the circulation.