Lactate Dehydrogenase (LDH) Isoenzymes Test

The lactate dehydrogenase (LDH) isoenzymes test is a laboratory procedure used to measure the levels of different forms of the enzyme lactate dehydrogenase in the blood or other bodily fluids. LDH is an enzyme found in many body tissues, including the heart, liver, kidney, skeletal muscle, brain, red blood cells, and lungs.

What are LDH Isoenzymes?

LDH isoenzymes are different forms of the LDH enzyme, each composed of four subunits. There are five main types of LDH isoenzymes, labeled LDH-1 to LDH-5, which vary in their composition and distribution in the body. Each type of LDH isoenzyme has a specific pattern of distribution in different tissues.

• LDH-1: Found primarily in heart muscle and red blood cells
• LDH-2: Found primarily in reticuloendothelial system
• LDH-3: Found primarily in lungs and other tissues
• LDH-4: Found primarily in skeletal muscle, kidney, and pancreas
• LDH-5: Found primarily in liver and striated muscle

Purpose of the Test

The LDH isoenzymes test is used to help diagnose and monitor a variety of conditions, including:

• Myocardial infarction (heart attack): Elevated levels of LDH-1 may indicate heart damage
• Liver disease: Elevated levels of LDH-5 may indicate liver damage or disease
• Muscle disorders: Elevated levels of LDH-4 and LDH-5 may indicate muscle damage or disease
• Cancer: Some types of cancer, such as testicular cancer, may cause elevated levels of certain LDH isoenzymes

How the Test is Performed

A blood sample is typically drawn from a vein in the arm and sent to a laboratory for analysis. The laboratory uses a technique called electrophoresis to separate the different LDH isoenzymes based on their size and charge. The levels of each LDH isoenzyme are then measured and compared to normal values.

Interpretation of Results

The results of the LDH isoenzymes test are interpreted in conjunction with other laboratory tests, medical history, and physical examination findings. Abnormal results may indicate tissue damage or disease, but must be considered in the context of the individual's overall clinical picture.

Frequently Asked Questions (FAQs)

What is the Lactate dehydrogenase (LDH) isoenzymes test?
A blood test that measures the levels of different LDH isoenzymes in the body.

Why is the LDH isoenzymes test performed?
To help diagnose and monitor various conditions, including tissue damage, cancer, and liver disease.

What are LDH isoenzymes?
Variants of the enzyme lactate dehydrogenase, which are found in different tissues and organs.

How many LDH isoenzymes are there?
Typically, five main isoenzymes are identified, labeled LDH-1 to LDH-5.

Which isoenzyme is typically elevated in heart damage?
LDH-1 and LDH-2 are often elevated in myocardial infarction.

Can the LDH isoenzymes test diagnose cancer?
Elevated levels of certain isoenzymes, such as LDH-4 and LDH-5, may be associated with some types of cancer, but it is not a definitive diagnostic tool.

What are normal ranges for LDH isoenzymes?
Normal ranges vary depending on the laboratory and testing method, typically reported in units per liter (U/L) or international units per liter (IU/L).

How is the test sample collected?
A blood sample is usually drawn from a vein in the arm.

Are there any preparations needed before the test?
Typically, no special preparation or fasting is required before the LDH isoenzymes test.