LFT's are a group of blood tests that provide information regarding the state of a Pt's liver.

The liver is involved with:

• Detoxification of blood:
  • Decomposes RBC
  • Plasma protein synthesis
• Stores glycogen
• Synthesizes:
  • Proteins
  • Hormones
  • Bile (to aid digestion)

• Albumin, a protein made specifically by the liver, and main constituent of total protein. Decreased in chronic liver disease (e.g. cirrhosis), nephrotic syndrome (lost through urine)
  • Protein gap, which is Total protein - Albumin, indicates loss of protein other than the major protein albumin, which is usualy Ig loss, e.g. in sepsis, chronic infection, cancers, autoimmune
• Bilirubin, including Total bilirubin, as well as Unconjugated bilirubin (aka Indirect) is a breakdown product of heme (in Hb of RBC's), and Conjugated bilirubin (aka Direct) (as the Liver conjugates bilirubin). SBR is an abbreviation for serum bilirubin. The types of bilirubin can differentiate between:
  • Prehepatic (e.g. hemolytic anemia), with normal Conjugated bilirubin, but elevated Unconjugated bilirubin - or Total bilirubin since Unconjugated = Total - Conjugated, indicating Liver is able to conjugate. Conjugated bilirubin is normally 0-0.3 mg/dL. Total bilirubin is usually 0.3-1.9 mg/dL
  • Hepatic (e.g. cirrhosis, viral hepatitis), with decreased Conjugated bilirubin, indicating Liver is unable to conjugate properly
  • Posthepatic (e.g. Bile duct obstruction), with elevated Conjugated bilirubin, indicating Liver is conjugating properly, but unable to excrete
• Liver enzymes (all ending in the suffix "-ase", which are leaked from the liver into blood, thereby being elevated in liver damage:
  • Liver transaminases, which are leaked by damaged liver cells (hepatocellular injury), thereby testing the integrity of liver parenchymal cells, indicating liver cell necrosis over cholestasis (bile blockage), including due to alcohol toxicity, viral hepatitis, drug induced, hepatitis, or if very shock. It includes:​
    • AST (Aspartate transaminase), which is not only found in the liver, but also heart, skeletal muscle, kidney, brains and RBC's. Thus, it is less specific for liver inflammation. Normal levels are 5-40 U/L. Especially if there is a high AST/ALT ratio, a muscle source should be considered, so check CK levels
    • ALT (Alanine transaminase), which indicates hepatocellular injury, including due to alcohol. Normal levels are 7-56 U/L
  • LDH (Lactate dehydrogenase), which is found in many body tissues including the liver. Elevated levels may indicate liver damage. Normal levels are 140-280 U/L
  • GGT, ALP, which provide information regarding the biliary tract (i.e. post-hepatic)
    • GGT (Gamma glutamyl transpeptidase) is found in many tissue, including the kidneys, bile duct, pancreas, gallbladder, spleen, heart, brain, and seminal vesicles. It is however, elevated in disease of the liver, biliary system, and pancreas. Normal range in adults is 8-65 U/L
    • ALP (Alkaline phosphatase), is present in all tissues throughout the entire body, but is particularly concentrated in the liver, bile duct, kidney, bone, intestinal mucosa and placenta (so elevated in pregnancy). Other LFT's should be also noted, because of its wide presence. Normally, it is 44-147 IU/L, but is significantly higher in kids and pregnant women

Patient information

These LFT's are EVERYWHERE Some are up, some are down. How do I know what is abnormal?!!
When the liver's not feeling too well, it can do one of two things - it can stop creating the things it's supposed to create. Or it leaks things it's supposed to retain.

What does the liver make. And what does it retain?
Enzymes (all ending in "-ase" is what the liver is supposed to retain, so it will all be up when the liver damaged. So I'm talking AST, ALT, GGT, ALP, and LDH). And things that the liver makes, like albumin, or conjugated bilirubin, will be down.

OK, but these liver enzymes can be divided into damage at the liver. And post-liver?
Yes, AST and ALT is at the liver. They both start with an A. GGT and ALP is after the liver, which you can memorize with the mnemonic that the Labor Party was started to put people 1st, but often puts the union leaders 1st, and the people last...

Urinalysis can also test for bilirubin.

It is useful to detect liver disease early, even though it may only cause mild Sx initially. These tests can help detect liver disease, distinguish the different types of liver disorders, gauge the extent of liver damage, and responses to taking certain medications to ensure the medications aren't damaging the Pt's liver.

• Lung function test (another abbreviation of LFT)
• Blood clotting testing
• Jaundice