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Laboratory: Clinical Biochemistry
Test Name:
Test Code: LD
Clinical Information:
Test Indications: Lactate dehydrogenase (LD or LDH) is an enzyme that is present in almost all body tissues. Elevated LDH is observed with liver disease, anemia, heart attack, bone fractures, muscle trauma, cancers, and infections such as encephalitis, meningitis, encephalitis, and HIV. Because LDH is non-specific, its measurements provide limited information, and alternate assays such as CK for muscle, ALT for liver, troponin for heart diseases, etc. are needed. LDH is also a non-specific marker of tissue turnover, which is a normal metabolic process.
Main clinical utility of LDH is in the areas of hematology and oncology. Marked increases (50x ULN) are seen in megaloblastic anemias. In addition, it is used as in vivo hemolysis marker in HELLP syndrome or to predict disease activity in leukemia. LDH serves as a robust predictor of poor outcomes in many neoplastic conditions.
LDH activity is affected by hemolysis of the blood sample (RBCs contain LDH) leading to falsely elevated results. Additionally, any cellular necrosis can lead to elevated plasma concentrations, and its ubiquitous tissue distribution limit its clinical utility as biomarker.
Collection Devices:
Specimen Required:

Plasma: 2.0 mL
Pediatric Plasma: 200.0 ┬ÁL

Pediatric: minimum volume for pediatric samples: plasma 200 uL

Stability 7 days at room temperature. LDH-4 & LDH-5 isoenzyme associated with liver and skeletal muscle are unstable in cooled and frozen samples. This may lead to incorrect LDH values in patients with liver or skeletal muscle disease or malignant tumors.
Serum: 2.0 mL

Do not refrigerate or freeze.

Samples must be transferred to an aliquot tube and stored at room temperature if analysis will not be complete within 48 hours (#110-10-05 Serum / Plasma Separation Procedure & Transport)
Reference Values:
0 - 4 wk: 290-800 U/L                                     
5 wk - 12 mo: 180-450
13 mo - 8 y: 190-400
9 - 14 y: 190-325   
15 - 16 y: 130-280
≥17 y:  100-250
Stat or Routine
See Also:
More Information:
Stability of LDH is 7 days at 15 - 25°C.  Samples must not be refrigerated or frozen due to instability of LDH-4 and LDH-5 at these temperatures. 
Method of Analysis: Enzymatic rate (NADH formation, spectrophotometric)