The LFTs or liver function tests measure the synthesis of proteins that are manufactured by the liver (clotting factors and albumin) and how effective the liver is in metabolism of drugs. These tests do not signify any specific system or disease process, but are indications of any serious disease or abnormality.
When any underlying abnormality is diagnosed in the liver function tests, then the inherent liver disease needs the primary care. But it is not easy to effectively locate a single abnormality, but the origin of the tissues is determined with the abnormalities of these tests.
But it is to be understood that an abnormal LFT is not necessarily an abnormal function. However, liver diseases are asymptomatic (shows no symptoms) and hence abnormal LFTS are not effectively investigated many times. So there is chance to miss and diagnose the correct treatment of a chronic liver disease.
The Most Common Liver Investigations are
In the reticuloendothelial system when the haem in the RBC is broken down then bilirubin is derived. The liver accepts this unconjugated bilirubin binding it with albumin. After conjugation it becomes water-soluble and gets excreted in the urine. The serum bilirubin is measurable and the conjugated and unconjugated are determined by the proportion of direct and indirect bilirubin respectively.
Low level of albumin is an effect of nutritional issues and marks hepatitic function. There is also protein loss due to a renal disease, protein synthesis fails too and there is a big loss of functioning liver tissues and some inflammatory situations when liver starts making other proteins.
The two main proteins, albumin and globulin are measured by this and is a normal feature of any live disease. When albumin levels fall, globulin levels increase. Acute infection, multiple myeloma and chronic inflammatory disease are symptoms when there is an over activity with the immune system.
Generally either alanine transferase (ALT) or aspartate amino transferase (AST) is measured where due to cell death or inflammation there is a leakage from the damaged cells. Since these proteins are located inside the cytoplasm the increase in levels give rise to hepatocellular damage. ALT is related more to the liver and AST with cardiac and skeletic muscles and RBCs.
Creatinine kinase (CK) establishes the source of elevated transferases. Lover diseases are more prone when the ALT and AST values are higher. The ratios between the two provides extra clues whether its chronic or if cirrhosis is already there.
There is an alteration GGT serum levels for all kinds of liver diseases. There is a bile duct damage and fibrosis when GGT is high in patients with chronic liver disease. To identify the causes of the altered ALP levels, the lack of specificity and sensitivity towards liver diseases are marked.
Alkaline Phosphatase (ALP)
The Alp is generated mainly from the cells lining bile ducts and in the bone too. When there is a marked elevation, it is a typical case of cholestasis and bone disorders. When the GGT concentration is normal but the ALP is high then its surely a bone disease. The analysis of isoenzyme helps to identify the source.