• How to make use of biochemical testing to aid in a diagnosis

Liver function tests (LFTs) are used to aid in determining if there may be a problem with an individuals liver, they test for things that are associated with liver function e.g. billirubin

the Fife LFT panel: Alb, ALT, ALP, Bil test for those only, however you can request for more tests e.g. Available separately: ygT, AST.

Alb (Albumin)

Pros

Main plasma protein

produced by liver

used as an assessment of liver synthetic function

ALT & AST

Pros

Cytoplasmic enzymes which are sensitive markers of acute damage to hepatocytes.

ALP (Alkaline phosphate)

Pros

Used to look for biliary epithelial damage & obstruction • increased in liver disease due to increased synthesis in response to cholestasis

ygT

Pros

Also used to look for biliary epithelial damage & obstruction. • “Super”-sensitive!

Billirubin

Pros

Breakdown product of haemoglobin: Unconjugated bilirubin taken up by liver & conjugated then excreted in bile. • Raised bilirubin results in clinical jaundice. • Used as an indicator of cholestasis.

overall LFT

Pros

Advantages -cheap, widely available, interpretable -direct subsequent investigation (e.g. imaging)

Cons

low albumin is normally found in some conditions, such as Post OP (due to redistribution)

significant malnutrition

nephrotic syndrome

Cons

Non-specific: found in cardiac muscle & erythrocytes as well as the liver • Also raised in e.g. – skeletal muscle disorders, – MI

Cons

ALP isoenzymes also present in bone, gut & placenta. • Raised in – physiological states e.g., pregnancy, childhood – bone is broken or in some bony diseases. – Induced by some drugs

Cons

Also present in bone, biliary tract, pancreas & kidney. • Affected by ingestion of alcohol and drugs such as phenytoin • May be over-sensitive?

Cons

Also raised in: – haemolysis – Hereditary hyperbilirubinaemias e.g. Gilbert’s syndrome.

Cons

Disadvantages – Do not assess liver “function” – Lack of complete organ specificity – Lack of disease specificity – May be “over-sensitive” – >40 years old, many newly discovered diseases for which they have no diagnostic value

• Highlight the limitations of biochemical testing which are useful but seldom diagnostic.

pros and cons above, they are useful tests but often not nearly specific enough, plus there are so many new diseases out now that these tests are N/A for

• Understand why good practice includes taking a good clinical history.

good clinical history is paramount as we require it to allow us to know what to explore next

also rem the golf ball toxicity licking story