The liver, located in the right upper portion of the abdominal cavity just beneath the right side of the rib cage, has many vital functions. Briefly, some of these functions are:

  • Detoxification of blood
  • Production of important clotting factor and other important proteins
  • Metabolizing (processing) medications and nutrients
  • Processing of waste products of hemoglobin
  • Storing of vitamins, fat, cholesterol, and bile
  • Production of glucose

In general, liver blood tests are used to detect an injury or an inflammation to the liver. These tests are commonly ordered and performed in many situations, such as in routine health screening, evaluation of abdominal pain, or suspected liver disease. The liver blood tests are typically done as a part of the comprehensive metabolic panel which also includes electrolyte levels and kidney function.

Liver blood tests are some of the most commonly performed blood tests. These tests can assess liver functions or liver injury. An initial step in detecting liver damage is a simple blood test to determine the presence of certain liver enzymes (proteins) in the blood.

Under normal circumstances, these enzymes reside within the cells of the liver. But when the liver is injured for any reason, these enzymes are spilled into the blood stream. Enzymes are proteins that are present throughout the body, each with a unique function. Enzymes help to speed up (catalyze) routine and necessary chemical reactions in the body.

Among the most sensitive and widely used liver enzymes are the aminotransferases. They include aspartate aminotransferase (AST or SGOT) and alanine aminotransferase (ALT or SGPT). These enzymes are normally contained within liver cells. If the liver is injured or damaged, the liver cells spill these enzymes into the blood, raising the enzyme levels in the blood and signaling liver disease.

The main values measured in liver blood tests are the aminotransferases (alanine aminotransferase or ALT and aspirate aminotransferase or AST). The other measurements include alkaline phosphate, albumin, and bilirubin. It is important to note that these tests are commonly referred to as “liver function tests”, but this term is misleading as the aminotransferases and alkaline phosphatase do not reflect the function of the liver. Strictly speaking, the true liver function tests (LFT’s) include albumin, bilirubin, blood coagulation panel, and glucose.

More specifically, AST, ALT, and alkaline phosphatase are called the liver enzymes and they typically are used to detect damage or injury to the liver (not its function)

AST (SGOT) is normally found in a variety of tissues including liver, heart, muscle, kidney, and brain. It is released into the serum when any one of these tissues is damaged. For example, its level in serum rises in heart attacks or with muscle disorders. It is therefore, not a highly specific indicator of liver injury as it can occur from other injured tissues.

ALT (SGPT) is, by contrast, normally found largely in the liver. This is not to say that it is exclusively located in liver, but that is where it is most concentrated. It is released into the bloodstream as the result of liver injury. Thus, it serves as a fairly specific indicator of liver status.

Abnormal liver tests may be detected in the blood in a variety of liver conditions:

  • Mild to moderate elevations of the liver enzymes are common.
  • Chronic hepatitis B and hepatitis C is a cause of chronic mild to moderate liver enzyme elevations.
  • Chronic and acute alcohol use is also a common cause of abnormal liver tests.
  • Some medications can cause mild to moderate increase in the liver enzymes.

A monospot test is a blood test that is used to help diagnose mononucleosis, also known as “mono. It is frequently ordered along with a CBC (complete blood count). The CBC is used to determine whether the number of white blood cells (WBCs) is elevated and whether a significant number of reactive lymphocytes are present.

The test works by detecting certain proteins called heterophile antibodies. The body makes these proteins to fight the Epstein-Barr virus (EBV) or cytomegalovirus (CMV) — the two viruses that cause mono.

A strep test may also be ordered with the mono test to determine whether a person’s sore throat is due to strep throat, a streptococcal infection instead of or in addition to mononucleosis.

If the mono test is initially negative, the doctor still suspects mono, he may order a repeat test in a week or so to see if heterophile antibodies  have developed and/or order one or more EBV antibodies to help confirm or rule out the presence of a current EBV infection.

Additional tests that can help your doctor make a mononucleosis diagnosis include:

  • A complete blood count (CBC) to see if your blood platelet count is lower than normal and if your lymphocytes (lymph cells) are abnormal
  • A chemistry panel to see if your liver enzymes are abnormal.

Epstein-Barr virus test is a blood test to detect antibodies to the Epstein-Barr virus (EBV) antigens. Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Epstein – Barr virus (EBV) antibodies are used to help diagnose Mono if you are symptomatic but have a negative Mono test. The Centers for Disease Control and Prevention (CDC) recommend ordering:

  • Viral capsid antigen (VCA)-IgM, VCA-IgG and D early antigen (EA-D) — to detect a current or recent infection
  • VCA-IgG and Epstein Barr nuclear antigen (EBNA) — to detect a previous infection

In pregnant women with symptoms of a viral illness, one or more of these EBV antibodies may be ordered along with tests for CMV, toxoplasmosis, and other infections (sometimes as part of a TORCH screen) to help distinguish between EBV and conditions that may cause similar symptoms.

Occasionally, a VCA-IgG or other EBV antibody may be repeated 2-4 weeks after the first test, either to see if a test changes from negative to positive or to measure changes in antibody concentrations to see if they rise or fall.

A VCA-IgG test, and sometimes an EBNA test, may be ordered on an asymptomatic patient to see if that person has been previously exposed to EBV or is susceptible to a primary EBV infection. This is not routinely done, but it may be ordered when a patient, such as an adolescent or an immune compromised patient, has been in close contact with a person who has Mono.