Lab test Glossary

Lab Test Glossary

Adiponectin: Adiponectin is a hormone produced by adipose (fat) tissue that influences the metabolism of lipids and glucose. Typically, as the amount of adipose tissue increases, the level of adiponectin decreases. Thus, adiponectin levels are usually decreased in individuals who are overweight and normal or elevated in individuals who are lean. Adiponectin has anti-inflammatory effects on the cells lining blood vessels (endothelial cells). Low levels of adiponectin (i.e., <4.0 ug/mL) are associated with low levels of HDL cholesterol, and increased levels of total cholesterol, LDL cholesterol, triglyceride, C-reactive protein, glucose, insulin, C-peptide, blood pressure, body mass index (BMI), tumor necrosis factor alpha and interleukin-8. In fact, research suggests that low adiponectin levels may be an independent risk factor for atherosclerosis. Conversely, high adiponectin levels are associated with a reduced risk of cardiovascular disease.
Alanine aminotransferase (ALT): Alanine aminotransferase (ALT) is an enzyme found predominantly in liver and, to a lesser extent, in the kidneys, heart, and skeletal muscle. Its level may be abnormally high in conditions that cause liver damage or after a heart attack. Serum levels of ALT are normally low; however, liver damage (for example, due to viral hepatitis) releases ALT into the bloodstream, causing its levels to rise. The ALT test is often done to determine liver function in conjunction with other tests, including aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bilirubin. Serum ALT levels are also increased as a result of some medications. ALT was formerly called serum glutamic pyruvic transaminase (SGPT).
Albumin: Albumin is a protein made by the liver and, therefore, is a good measure of liver function. When the liver is injured or diseased, it loses its ability to make albumin, resulting in decreased levels. Decreased levels can also be seen in kidney disease, which allows albumin to escape into the urine, or may be caused by malnutrition or a low-protein diet. Increased levels of albumin can be seen in cases of dehydration.
Albumin/Globulin ratio: The ratio of albumin to globulin in the blood may be abnormal in certain blood and immune system conditions as well as some liver and kidney diseases. A low albumin/globulin ratio may be due to overproduction of gamma-globulin, as seen in monoclonal/polyclonal gammopathy, multiple myeloma or autoimmune diseases. A low ratio could also be due to low levels of albumin, due to low production, as in cirrhosis, or excessive loss, as in nephrotic syndrome or protein-losing enteropathy. A high ratio suggests disorders involving low gamma-globulin production, such as agammaglobulinemia.
Alkaline phosphatase (ALP): Alkaline phosphatase (ALP) is an enzyme found in many tissues, including liver, bile duct, placenta, and bone. Its level may be elevated in conditions that damage or disrupt the liver, bile ducts, or bone. ALP may be increased in some normal circumstances, (e.g., normal bone growth or third trimester pregnancy) or in response to a variety of drugs. The ALP test is often done to determine liver function in conjunction with other tests, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin.
Alpha-1-antitrypsin (A1AT): Alpha-1-Antitrypsin (A1AT) is a protein that circulates in the blood and it is produced mostly by the liver. Its purpose is to protect the tissues in the body from being damaged. In the lungs, for example, low-levels of A1AT can lead to damage of the delicate gas exchange region of the lungs (alveoli), which can lead to the early development of emphysema. A deficiency of A1AT can also lead to liver disease. Low levels can be found in neonatal respiratory distress syndrome and severe protein-losing disorders. In some adults, A1AT deficiency is complicated by cirrhosis, liver cancer, rheumatoid arthritis, and pancreatitis. Increased levels may be associated with inflammation.
Alpha-2-macroglobulin (A2M): Alpha-2-macroglobulin (A2M) is a major blood protein that may be abnormal in certain liver, kidney, and pancreas conditions. Elevated levels are seen in conditions such as cirrhosis, nephrotic syndrome, severe burns, and diabetes. Decreased levels are seen in pancreatitis, fibrinolysis, and liver disease.
Alpha-fetoprotein (AFP): Alpha-fetoprotein (AFP) is produced by the fetus and, thus, is present in the mother’s blood during pregnancy. Levels in adult males and non-pregnant females are normally very low. High levels of AFP can be seen in people with liver cancer and in men with early stage testicular cancer. Less frequently, high levels are seen in other malignancies such as stomach, biliary and pancreatic cancer.
Amylase: Amylase is a digestive enzyme produced in the salivary glands and pancreas. Its levels may be elevated if the pancreas is inflamed or damaged. High levels are seen in both acute and chronic pancreatitis as well as other diseases such as gall bladder disease, ectopic pregnancy and pulmonary infarction.
Androstenedione: Androstenedione is a steroid hormone that is modified within the body to produce the male sex hormone testosterone and the female sex hormone estrogen. Taken orally, androstenedione will increase blood levels of testosterone. Increased levels can be seen in adrenal tumors, Cushing’s syndrome, and polycystic ovarian syndrome. Decreased levels can be seen in some glandular conditions such as hypogonadism and adrenal insufficiency.
Anti-nuclear antibody (ANA): Anti-nuclear antibodies (ANA) can bind to certain structures within the nuclei of our cells. In the blood, ANAs may be detected in a variety of autoimmune diseases and arthritis conditions or even in some people who do not have any specific disease. ANAs are helpful in the evaluation of systemic lupus erythematosus (SLE) and drug induced lupus. Elevated levels may also be positive in cases of scleroderma, Sjogren’s syndrome, Raynaud’s disease, juvenile chronic arthritis, rheumatoid arthritis, antiphospholipid antibody syndrome, autoimmune hepatitis, type 1 diabetes, and many other autoimmune and non-rheumatological conditions associated with tissue damage. Due to the many potential causes of a positive result, additional testing is often needed.
Anti-Sa charomyces cerevisiae antibody (ASCA): Anti-Saccharomyces cerevisiae antibody (ASCA) testing may be useful in the evaluation of suspected inflammatory bowel disease, including Crohn’s disease and ulcerative colitis.
Apolipoprotein A1 (Apo A1): Apolipoprotein A1 (Apo A1) is the major component of HDL or “good cholesterol”. Apo A1 is instrumental in promoting the transfer of cholesterol to the liver, where it is metabolized and then excreted from the body. Very low levels of Apo A1 are associated with a higher risk for cardiovascular disease because of the decreased ability to clear cholesterol from the body. High levels are considered somewhat protective because of the increased ability to clear cholesterol from the body. Apo A1 is considered to be a better indicator of cardiovascular risk than HDL cholesterol.
Apolipoprotein CIII (Apo CIII): Apolipoprotein CIII (Apo CIII) is made in the liver and is found in very-lowdensity lipoprotein (VLDL) and high-density lipoprotein (HDL) particles. Very low levels of Apo CIII may be associated with a higher risk of coronary heart disease. Apo CIII has been recognized as an emerging risk biomarker that may play a role in more effective coronary artery disease (CAD) risk assessment.
Apolipoprotein H (Apo H): Apolipoprotein H (Apo H) is made primarily by the placenta and is also called beta-2 glycoprotein. A major role of this biomarker is to protect against the formation of blood clots. Thus, some people who possess decreased levels of this biomarker may have an increased risk of developing a blood clot (thrombus). Decreased levels of apo H are most often due to an autoantibody directed against this biomarker. This autoantibody is referred to as beta-2 glycoprotein antibody, and individuals who have this antibody may possess the antiphospholipid syndrome. The antiphospholipid syndrome is a blood clotting disorder, which can cause recurrent miscarriage. It is also associated with an increased risk of venous and arterial blood clotting.
Aspartate aminotransferase antigen (AST Ag): AST antigen (AST Ag) is an enzyme present in liver and muscle cells. Its levels are elevated in conditions affecting the heart and liver, such as viral hepatitis, hepatic congestion, myocarditis and myocardial infarction.
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