LDBF - Clinical: Lactate Dehydrogenase (LD), Body Fluid

Test Catalog

Test Name

Test ID: LDBF    
Lactate Dehydrogenase (LD), Body Fluid

Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of exudative pleural effusions

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Lactate dehydrogenase (LD) activity is present in all cells of the body with highest concentrations in heart, liver, muscle, kidney, lung, and erythrocytes.


Pleural Fluid:

Measurement of LD in body fluids is primarily indicated to aid in the differentiation of transudative and exudative effusions as LD activity is considered an indicator of the extent of inflammation. Dr. Richard Light derived criteria in the 1970s for patients with pleural effusions that are still used today.(1)


The criteria include the measurement of total protein and LD in pleural fluid and serum. Exudates are defined as meeting 1 of the following criteria:

1. Pleural fluid-to-serum protein ratio above 0.5

2. Pleural fluid LD above two-thirds the upper limit of normal serum LD

3. Pleural fluid-to-serum LD ratio above 0.6


Pericardial fluid:

The routine analysis of LD to differentiate exudative and transudative pericardial effusions is not considered helpful.(2)


Peritoneal fluid:

Ascitic fluid LD has reported utility in differentiating secondary bacterial peritonitis from spontaneous bacterial peritonitis when at least 2 of 3 criteria are met in ascites fluid: total protein above 1.0 g/dL, glucose below 50 mg/dL, and LD above the upper reference limit for serum.(3)


Spinal fluid (CSF):

LD is not measured in CSF routinely. Release of LD into CSF occurs as a consequence of cell death. Therefore, LD is a nonspecific marker of cell necrosis and may be raised in a number of pathologic conditions, including meningitis(4) with normal concentrations reported as less than 24 U/L. CSF LDH is also increased in primary brain tumors, central nervous system metastases, hydrocephalus, and cerebral ischemia.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


Interpretation Provides information to assist in interpretation of the test results

Elevated lactate dehydrogenase in pleural fluid is consistent with exudative effusions.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Lactate dehydrogenase activity may be falsely elevated in samples that contain blood due to trauma during collection.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Light RW: The Light criteria: the beginning and why they are useful 40 years later. Clin Chest Med 2013 Mar;34(1):21-26

2. Ben-Horin S, Bank I, Shinfeld A, et al: Diagnostic value of the biochemical composition of pericardial effusions in patients undergoing pericardiocentesis. Am J Cardiol 2007 May 1;99(9):1294-1297

3. Soriano G, Castellote J, Alvarez C, et al: Secondary bacterial peritonitis in cirrhosis: a retrospective study of clinical and analytical characteristics, diagnosis and management. J Hepatol 2010;52:39-44

4. Knight JA, Dudek SM, Haymond RE: Early (chemical) diagnosis of bacterial meningitis: cerebrospinal fluid glucose, lactate, and lactate dehydrogenase compared. Clin Chem 1981;27:1431–1434