LDH is a blood test that measures the amount of an enzyme in the blood called "lactate dehydrogenase" (LDH). Chemically, LDH is involved in the conversion of pyruvate and lactate in the body. For example, the accumulation of lactate is the cause of sore muscles after a heavy workout.
LD, lactate dehydrogenase, lactic dehydrogenase, total LDH, LDH isoenzymes
Why the Test Is Performed
In general, the LDH level is measured in order to check for tissue damage, especially to the heart, liver, kidney, skeletal muscle, brain, and lungs — all of which elevates the normally low LDH level in the blood. For patients with melanoma, it is used to determine if the cancer has metastasized (spread) to organs beyond the skin or lymph nodes; this usually occurs in the liver or lungs. Although LDH is not specific for melanoma, it may be useful at diagnosis or to monitor post-surgery (adjuvant) treatment. The staging system for melanoma uses the LDH level to subdivide patients with stage IV disease.
How the Test is Performed
The healthcare provider draws blood from a vein or from a heel, finger, toe or earlobe. The laboratory then quickly spins (centrifuges) the blood to separate the serum (liquid portion) from the cells. The LDH test is done on the serum.
How to Prepare for the Test
Your healthcare provider may ask you to stop taking drugs that may affect the test. Drugs that can increase LDH measurements include alcohol, anesthetics, aspirin, clofibrate, fluorides, mithramycin, narcotics, and procainamide. Ascorbic acid (vitamin C) can lower levels of LDH.
Normal values may vary depending on your age, sex, and the specific method used in the laboratory. A typical range is 105-333 IU/L (international units per liter). The total LDH is often further separated into five components (called isoenzymes) -- LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5 -- that are specific to certain regions of the body and are expressed as percentages of the total.
What Abnormal Results Mean
LDH level can be elevated in many conditions, not just metastatic melanoma. Higher-than-normal levels may also indicate:
- heart attack
- various kinds of anemia
- low blood pressure
- liver disease (for example, hepatitis)
- muscle injury
- muscular dystrophy
Falsely elevated results can result if the blood specimen was handled roughly, stored in extreme temperatures, or if the sample was difficult to collect.
Multiple prior studies have shown that an elevated LDH level can predict survival in patients with advanced melanoma. For this reason, it was included in the 2002 staging system for melanoma. Patients with stage IV melanoma and elevated LDH have the worst prognosis of any stage of the disease.
Beyond categorizing patients with stage IV disease, the LDH test is actually not very specific or sensitive for detecting melanoma metastases in the first place. For example, a recent study followed patients with melanoma for 2.5 years after surgery. The results showed that LDH level was not a good marker for "in transit metastasis" (stage IIIC melanoma that has spread beyond the skin lesion but not to the lymph nodes) or spread to local lymph nodes. Furthermore, it only accurately identified distant metastasis in a minority of patients. A test for another blood protein called S-100B is emerging as a better marker than LDH and so may be incorporated into future staging systems.
If your doctor has ordered a test for LDH, or even if the results come back and the level is high, there is no reason to panic. LDH is not a reliable marker of metastatic melanoma, so a high level is only a "head's up" for the doctor to investigate the situation further with a CT/PET/MRI scan or sentinel lymph node biopsy. If you have any questions or concerns about interpreting your LDH test results, be sure to discuss them with your doctor.
Egberts F, Hitschler WN, Weichenthal M, Hauschild A. "Prospective monitoring of adjuvant treatment in high-risk melanoma patients: lactate dehydrogenase and protein S-100B as indicators of relapse" Melanoma Research 2008. 26 February 2009.
Chun YS, Wang Y, Wang DY, et al. "Prognostic value of S100B levels and LDH levels in melanoma patients" J Clin Oncol 2008 26(May 20 suppl; abstr 9002). 26 February 2009.
Eggermont AMM. "Reaching First Base in the Treatment of Metastatic Melanoma" J Clin Oncol 2006 24(29):4738-45. 26 February 2009.