Before
understanding when the test would be required, it is important to know the
importance of the enzyme lactate dehydrogenase. LDH is required when sugar is
being turned into energy in the cells. This enzyme can be found in lots of
organs and tissues and throughout the body. It is quite common in the skeletal
muscles, the kidneys, heart, pancreas, liver, blood cells and even the lymph
tissues.
The LDH might be released into the bloodstream when there is an injury
in these tissues or organs. Thus the level of LDH in the blood would rise. The
high levels of the enzyme in the blood would mean that there has been some form
of chronic or acute cell damage. Though the LDH test would be able to tell if
there has been some form of damage, additional tests would be required to find
out the actual source of the problem. Very low levels of the enzyme can occur
but only in rare cases and that is not harmful.
Are there any subtypes
of the LDH enzymes?
The LDH is
available in five different forms and these forms are called isoenzymes. They
can be distinguished from the slight difference that exists in their
structures. They are termed as LDH-1, LDH-2, LDH-3, LDH-4 and the last one is
LDH-5. The different forms are found in different tissues. The areas where each
type has the highest concentrations are as follows:
LDH-1 - heart and the
red blood cells
LDH-2 - same as LDH-1
LDH-3 - lungs,
pancreas, lymph tissues and the platelets
LDH-4 - liver and the
skeletal muscles
LDH-5 - same as LDH-4
What is the role of
the LDH test and how would it proceed?
Through the test,
the doctors can measure the levels of LDH in the patient's blood. The doctors
can even measure the LDH levels in cerebrospinal fluid or the urine. The
technician would be drawing the blood from a vein at the elbow crease. The back
of the hand is also preferred at times. The technician would be cleaning the
area with antiseptic and tie the elastic band for easy drawing of blood.
The
needle would then be inserted into the vein and blood is drawn. The needles and
elastic bands are removed after successful withdrawal of blood. The process is
quite similar to the test measuring the t3 normal range. A sharp tool called a
lancet might be used for infants to receive blood samples. A bandage might be
placed over the cut.
Certain medications
and drugs can interfere with the results of the LDH test. For instance, a large
amount of ascorbic acid or vitamin C might lower the levels of LDH. Aspirin,
aesthetics, procainamide, alcohol and narcotics might raise the levels. The
same can happen through strenuous exercise. The clotting time should be
analysed as well. The doctor should be asked about the medications to be
avoided before the test.
What is indicated
by the test results?
The levels of LDH
vary with age. The LDH levels would be quite high in small children and
infants. The results are generally reported in units per litre. The normal
ranges are as follows:
0 - 10 days: 290 - 2000
U/L
11 days - 2 years: 180
- 430 U/L
2 - 12 years: 110 - 29
U/L
More than 12 years: 100
- 190 U/L
The doctors are
able to evaluate the medical conditions depending on the LDH values. The normal
ranges can vary with age. The usefulness of monitoring the LDH values in
certain disorders and conditions are increasing with increasing research in the
field.
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