What are the other Names for this Test? (Equivalent Terms)

• Lactic Acid Test
• L-Lactate Test

What is Lactate Test? (Background Information)

• A Lactate Test (or Lactic Acid Test) measures the level of lactate in blood, cerebrospinal fluid (CSF), pleural fluid, or in peritoneal fluid
• Generally, when carbohydrates are broken down in the presence of adequate oxygen, the by-products are water and carbon dioxide. However, when the carbohydrate breakdown occurs in low oxygen (anaerobic) environment, the end result is a production of lactic acid
• The energy cycle within the cells occurs within the mitochondria, which utilizes glucose and oxygen to generate ATP (adenosine triphosphate). ATP is considered to be the ‘energy currency’ of the human tissue
• Lactic acid that is generated during anaerobic environment is broken down by liver. Persistent increase in lactic acid results in a condition called lactic acidosis, wherein the pH of the individual decreases resulting in a variety of symptoms, such as nausea, vomiting, rapid respirations, and weakness in muscles
• In conditions where significant liver damage is present, the lactic acid levels also increases, due to a decrease in its breakdown. In an individual who is diabetic and taking medication (Metformin), severe lactic acidosis may develop in a background of infection, renal failure, or congestive heart failure

Lactic acidosis can be classified into two categories, namely type A and type B:

• Type A lactic acidosis occurs due to decreased oxygen absorption in the lungs, or due to decreased blood flow, resulting in lack of oxygen to the tissues
• Type B lactic acidosis results in an environment, wherein an increase of lactic acidosis occurs in the blood, but not in a background of decreased oxygen environment

Type B lactic acidosis is caused by clinical conditions, such as acute renal failure, chronic renal failure, severe diabetes, liver failure, and chemotherapy, a variety of tumors, acute lymphoblastic and acute myeloblasticleukemias, severe infections, and excessive exercise. Type A lactic acidosis results from congestive heart failure, acute respiratory failure, sudden and excessive blood loss.

What are the Clinical Indications for performing the Lactate Test?

• The Lactate Test is usually performed to determine the severity of clinical conditions resulting in lactic acidosis
• It can be performed to determine the level of hypoxia (lack of oxygen) and the responsiveness to therapy in congestive heart failure, severe infection, effect of certain drug overdose, and severity of liver disease
• Lactic Acid Test can be performed on cerebrospinal fluid to distinguish between bacterial meningitis (with high lactic acid level) and viral meningitis (in which the lactic acid level is not elevated)

How is the Specimen Collected for Lactate Test?

Specimen required: Blood for blood lactic acid level, cerebrospinal fluid (CSF) for CSF level, pleural fluid for pleural fluid levels, and peritoneal fluid for peritoneal fluid levels.

Process:

• The blood is procured by inserting a needle into a superficial vein of the arm
• For CSF level, a needle is inserted into your spine to collect CSF fluid for analysis
• For pleural and peritoneal levels, a needle is inserted into the pleural cavity (a procedure called thoracentesis), or peritoneal cavity (a procedure called paracentesis), for collecting fluids for analysis

Preparation required: No special preparation is required prior to testing for lactic acid.

Note: It is important not to clinch your fist during the blood sample collection, since it may falsely elevate the level of lactic acid, in the sample.

What is the Significance of the Lactate Test Result?

An elevated lactic acid level can be seen in a variety of clinical conditions, which include:

• Severe congestive heart failure
• Heart attack
• Bacterial meningitis
• Liver failure
• Severe infection
• Overdose from alcohol, methanol, and ethylene glycol (generally found in anti-freeze)
• Inherited metabolic disorders
• Inherited mitochondrial disorders
• Intake of certain medications, such as Glucophage and Isoniazid (used for treatment of tuberculosis)

 The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

• Increased lactic acid levels have been noted with vitamin B1 deficiency
• Sometimes, your physician may order an arterial lactic acid test specifically instead of a venous lactic acid test. This is because the lactic acid measurement from an arterial blood sample is thought to be more reflective, of the actual lactic acid level in blood
• Lactic acid levels in pleural fluid and peritoneal fluid may be performed to determine infection of pleural cavity and peritoneal cavity, respectively

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.