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Understanding Liver Tests

Liver function tests (LFT) are screening tools that help your doctor in evaluating your liver functions. As there are several functions that are carried out by the liver, a single test will not be sufficient to detect liver dysfunction. Here is a comprehensive list of liver tests carried out and a detailed procedure on how they will be performed for your better understanding.

Serum albumin:

Serum albumin test is performed to measure the amount of albumin in the clear portion of the blood. Albumin is a protein substance produced in the liver. This test is done by collecting a blood sample. Lower levels of serum albumin may indicate possibility of kidney disease or liver diseases such as hepatitis, cirrhosis, and ascites.

Alkaline phosphatase:

Alkaline phosphatase (ALP) is performed to measure the level of ALP in the blood, which is a protein found in every tissue in the body. This test is also done by collecting a blood sample. Higher levels of ALP are found in the liver, bile ducts and bone. Your doctor will advise you to avoid eating or drinking for about six hours prior to the test. Certain medicines will alter the levels of ALP in the blood. Hence, your doctor will instruct you to discontinue them before the test.

This test helps doctors to diagnose liver or bone disease and monitor the progress of treatment for the same. High ALP levels can indicate biliary obstruction, bone disease, hepatitis, leukemia, liver disease, lymphoma, bone tumors, osteomalacia, rickets, and sarcoidosis. Children during growth spurts and pregnant women will have higher levels of ALP, which is considered normal. Less than normal levels of ALP are mainly because of malnutrition, protein deficiency and Wilson’s disease.

Alanine transaminase:

Alanine transaminase (ALT) is an enzyme mainly found in liver and any injury to liver will lead to the release of this enzyme into the bloodstream. This test helps doctor to find out whether there is damage in the liver. Normal values are influenced by factors such as age, gender and may slightly vary between different laboratories. Your doctor will explain to you about the test results and what they indicate. Higher levels of ALT indicate the presence of liver disease such as cirrhosis, liver necrosis, hepatitis, liver ischemia and liver tumor.

Aspartate aminotransferase:

Aspartate aminotransferase (AST) is an enzyme found in high levels in heart muscle, liver, and muscle cells. This test along with other tests helps doctors to diagnose and monitor liver disease. Increased levels of AST in blood indicate acute kidney failure, cirrhosis, heart attack, hepatitis, hemolytic anemia, liver tumor and liver ischemia.

Alpha-1 antitrypsin:

Alpha-1 antitrypsin test is carried out to measure the amount of alpha-1 antitrypsin (A1AT) in the blood. This test identifies A1AT deficiency, which may lead to rare type of emphysema (lung disease) in adults and liver disease or cirrhosis in children. In the case of A1AT deficiency, liver fails to produce enough protein, essential for the protection of the lungs and the liver. Lower levels of A1AT indicate abnormality in the gene that produces A1AT. Usually, a normal individual will have two copies of the gene. Patients with decreased A1AT will possess one normal and one abnormal gene. Lower than accepted levels of A1AT may be found in conditions such as cirrhosis, emphysema, liver tumors, obstructive jaundice, and portal hypertension.

Gamma-glutamyl Transpeptidase:

Gamma-glutamyl transpeptidase (GGT) test measures the amount of the enzyme GGT in the blood. Prior to this test, your doctor will advise you to discontinue any medicines that may alter the GGT levels. This test is performed along with other tests such as the ALT, ALP, and bilirubin tests to detect liver disease, bile duct disease and bone disease. The results with more than normal levels of GGT may point towards alcohol abuse, cholestasis, heart failure, hepatitis, liver ischemia, liver tumor, cirrhosis and liver necrosis.

Prothrombin time:

Prothrombin time (PT) is a blood test carried out to calculate the time required for the liquid portion (plasma) of the blood to clot. During the test, blood withdrawn from one of the veins will be collected in an airtight container. Certain chemical agents will be added to the blood sample after which the time needed for the plasma to clot will be calculated. This test measures the ability of clotting factors that help in blood clotting.  The normal time required for the blood to clot is between 11 and 13.5 seconds. The PT will be prolonged if the necessary blood clotting factors are deficient or ineffective. Increased PT may indicate bile duct obstruction, liver disease, malabsorption and vitamin K deficiency.

Serum bilirubin:

Bilirubin test measures the amount of bilirubin pigment in the blood, which is usually found in the liver. The liver is responsible for the breakdown of bilirubin formed during the replacement of older red blood cells (RBCs). Your doctor will instruct you to avoid eating or drinking for four hours prior to the test. Inform your doctor about the regular medicines you take as few drugs alter the bilirubin levels in blood. High amounts of bilirubin in the blood indicate jaundice, liver diseases such as hepatitis, cirrhosis, and gallbladder problems such as biliary stricture, gallstones and gallbladder cancer.

Urine bilirubin:

Urine bilirubin helps in diagnosis of liver and gallbladder problems. The test can be performed using any urine sample, i.e. urine passed at any time of the day. However, a 24-hour urine sample is more conclusive. Your doctor may advise you to avoid intake of certain medications that may affect the test results. Normally, there should be no bilirubin found in the urine. Increased amounts of bilirubin in the urine may be due to underlying diseases such as cirrhosis, gallstones, hepatitis, liver tumors, and biliary tract disease.