Test ID LD_I Lactate Dehydrogenase (LD) Isoenzymes, Serum
Useful For
Investigating a variety of diseases involving the heart, liver, muscle, kidney, lung, and blood
Differentiating heart-synthesized lactate dehydrogenase (LD) from liver and other sources
As an aid in the diagnosis of myocardial infarction when used in combination with total creatine kinase (CK) and CK-MB
Investigating unexplained causes of LD elevations
Detection of macro-LD
Profile Information
Test ID | Reporting Name | Available Separately | Always Performed |
---|---|---|---|
LD | Lactate Dehydrogenase (LD), S | Yes | Yes |
LDI | LD Isoenzymes, S | No | Yes |
Method Name
LDI: Electrophoresis Densitometry
LD: Photometric Rate
Reporting Name
Lactate Dehydrogenase Isoenzymes, SSpecimen Type
SerumContainer/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 2 mL divided into 2 tubes each containing 1 mL
Additional Information: Patient's age is required.
Specimen Minimum Volume
0.75 mL
Specimen Stability Information
Specimen Type | Temperature | Time |
---|---|---|
Serum | Ambient (preferred) | 7 days |
Refrigerated | 48 hours |
Clinical Information
Total Lactate Dehydrogenase (LD):
LD activity is present in all cells of the body with highest concentrations in heart, liver, muscle, kidney, lung, and erythrocytes. As with other proteins used as tissue-function markers, the appearance of LD in the serum occurs only after prolonged hypoxia and is elevated in a number of clinical conditions including cardiorespiratory diseases, malignancy, hemolysis, and disorders of the liver, kidneys, lung, and muscle.
Isoenzymes:
LD is a tetrameric cytoplasmic enzyme, composed of H and M subunits. The most usual designation of the isoenzyme is LD-I (H4), LD-II (H3M), LD-III (H2M2), LD-IV (HM3), and LD-V (M4). Tissue specificity is derived from the fact that there is tissue-specific synthesis of subunits in well-defined ratios. Most notably, heart muscle cells preferentially synthesize H subunits, while liver cells synthesize M subunits nearly exclusively. Skeletal muscle also synthesizes largely M subunits so that LD-V is both a liver and skeletal muscle form of LD. The LD-I and LD-V forms are most often used to indicate heart or liver pathology, respectively.
LD-I appears elevated in the serum about 24 to 48 hours after a myocardial infarction (MI), but is generally not as useful as troponin or creatine kinase-MB (CK-MB) for detection of MI, unless the MI occurred at least 24 hours prior to testing. Normally, LD-II is greater than LD-I; however, when a MI has occurred, there is a "flip" in the usual ratio of LD-I/LD-II from <1 to >1 (or at least >0.9). Use of the ratio for evaluation of patients with possible cardiovascular injury has largely been replaced by TPNT / Troponin T, Serum.
The LD-V form is pronounced in patients with either primary liver disease or liver hypoxia secondary to decreased perfusion, such as occurs following an MI. However, LD-V is usually not as reliable as the transaminases (eg, aspartate aminotransferase, alanine aminotransferase) for evaluating liver function. LD-V also may be elevated in muscular damage and diseases of the skin.
Although it does not appear to cause or be associated with any symptoms or particular diseases, the presence of macro-LD (LD combined with an immunoglobulin) can cause an idiosyncratic elevation of total LD.
Reference Values
LD
1-30 days: 135-750 U/L
31 days-11 months: 180-435 U/L
1-3 years: 160-370 U/L
4-6 years: 145-345 U/L
7-9 years: 143-290 U/L
10-12 years: 120-293 U/L
13-15 years: 110-283 U/L
16-17 years: 105-233 U/L
≥18 years: 122-222 U/L
LD ISOENZYMES
I (fast band): 17.5-28.3%
II: 30.4-36.4%
III: 19.2-24.8%
IV: 9.6-15.6%
V (slow band): 5.5-12.7%
Cautions
A hemolyzed specimen is not acceptable as red blood cells contain much more lactate dehydrogenase (LD) than serum. Causes of hemolysis can include transportation via pneumatic tube, vigorous mixing, or traumatic venipuncture. Tubes should be void of air bubbles to prevent minor hemolysis. LD activity is one of the most sensitive indicators of in vitro hemolysis. Hemolysis causes anomalous elevation of LD-I such that any ex vivo hemolysis must be strictly avoided.
Freezing or prolonged storage at 4° C (>12 hours) causes LD-V to be lost.
Elevations of intermediate forms, LD-II through LD-IV, are rarely used to define a tissue of origin and such reports are largely anecdotal.
While increases in serum LD also are seen following an myocardial infarction, the test has been replaced by the determination of troponin (TPNT / Troponin T, Serum).
Day(s) Performed
LD: Monday through Sunday; Continuously
LD isoenzymes: Tuesday, Thursday, Saturday; 10 a.m.
Report Available
1 day-LD Total ; 3 days- LD IsoenzymesPerforming Laboratory

Test Classification
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
83615-LD
83625-LD isoenzymes