Explain the manner in which the isoenzymes of LDH can be used as diagnostic test

Currently, the main use for LDH is as a general indicator of the existence and severity of acute or chronic tissue damage and, sometimes, as a monitor of progressive conditions such as some cancers, kidney disease, and liver disease. It used to be ordered to help diagnose and monitor a heart attack, but the troponin testhas largely replaced LDH in this role. LDH isoenzymes may be used in differential diagnosis to help determine which organs are likely to be involved.

LDH is used in medicinal use as a marker of tissue breakdown and can function as a marker for hemolysis. It can be used as a marker for myocardial infarction, more commonly known as heart attacks. Following a myocardial infarction, levels of LDH peak at three to four days, and remain elevated for up to ten days. In this way, elevated levels of LDH can be useful for determining if a patient has had a myocardial infarction, if they came to a doctor several days after an episode of chest pain. So the presence of elevated levels of LDH can be of great assistance in locating damaged tissue, particularly that of the cardiovascular system.

Lactic dehydrogenase or LDH is an enzyme that is required to catalyze the chemical reaction that results in pyruvic acids getting converted to lactic acids and vice versa. This enzyme is present in almost all the cells of the human body though in different forms. There are 5 main isoenzymes of LDH that are referred to as LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5. In the heart and blood cells, the enothilial cells, the cells making up the lungs, the cells of the kidneys and pancreas and in the cells of the liver the isoenzyme with the highest concentration is LDH-1, LDH-2, LDH-3, LDH-4 and LDH-5 respectively.

The change in concentration of different isoenzymes in each of these cells can be used as a diagnostic tool to identify and prevent injury.

For example, if a test reveals that the LDH-1 concentration is greater than the LDH-2 concentration in blood, it could indicate that the patient had a heart attack in the last week as normally the concentration of LDH-2 is higher than that of LDH-1. It is also possible to detect a heart attack using an ECG but for an accurate diagnosis, the ECG should be conducted within 10 minutes of a person having a heart attack.