clinical biochemistry

testing for biomarker (3)

1. take sample

2. chemical and biochemical analysis to detect biomarkers

3. compare to references

plasma vs. serum

serum has clotting factors,

plasma has been treated with anticoagulants

• serum = plasma - fibrinogen

Blue cap

reversible inhibition of clotting

clotting tests

yellow cap

allows clots,

serum for analysis of soluble components

pink/ purple cap

irreversible inhibition of clotting

blood cell/ plts analysis

green cap

anticoagulant

hormone/chromosome analysis

Grey cap

halts metabolism

analysis of energy sources, glucose

diagnostic biomarkers

they detect disease/ conditions

monitoring biomarkers

to assess status of disease

prognostic biomarkers

they predict disease progression

risk biomarkers

to see the transition from healthy to diseased

how do biomarkers levels change with extensive cell damage?

intracellular molecules (cell type specific) released

how do biomarkers levels change with cell proliferation?

increased markers of cell growth / rapid proliferation produced by cells

how do biomarkers levels change with enzyme induction?

increased expression of cell specific membranes

how do biomarkers levels change with duct obstruction?

blocked flow of molecules

increased in blood

spectroscopy with analysis of markers

colorimetric assays, chemical rxns, increased enzyme activity

chromatography with analysis of markers

molecule separation based on size

mass spectrometry with analysis of markers

molecule identification based on mass

immunoassays with analysis of markers

molecule identification based on molecular sequence/strructure

detected w/ antibodies

molecular techniques with analysis of markers

DNA/RNA sequencing to identify infection and genetic markers

POCT

point of care testing

patient present

rapid turnaround

non-laboratory

Clinical Biochemistry Department

labs

greater range of test

automated

Good Biomarkers should have:

• specificity

• biological understanding

• reproducibility

• efficient

• cost effective

• feasible sample collection

• better than gold standard

• sensitivity

pre- analytical factors affecting test result

• technical - correct patient and correct labelling of sample

• biological - age, gender, mass, ethnicity

analytical factors affecting test result

accuracy and precision

post analytical factors affecting test result

reporting, transmission, transcript, clinical decision

how is reference range calculated

$\mu$ ± 2SD

Liver Functions (4)

• blood proteins production- albumin, clotting factors

• bile production

• bilirubin excretion- haem breakdown

• phagocytosis of bacteria- via kupffer cells

metabolism and detox in the liver

• glycogen → glucose

• fatty acid metabolism -ketone production

• a.a. metabolism - ammonia→ urea

pre-hepatic with bilirubin as a biomarker

• high serum of unconjugated bilirubin

• other LFT normal

• eg. haemolytic disease

hepatic with bilirubin as a biomarker

• high serum of conjugated bilirubin

• liver enzymes elevated, liver damage

• eg. hepatitis

post-hepatic with bilirubin as a biomarker

• high serum of conjugated bilirubin

• blockage of bile flow-cholestasis

• eg. gallstones

LFT meaning

liver function test

elevated unconjugated bilirubin means…

• increased bilirubin synthesis

• haemolytic disease

• decreased conjugation by liver → genetic disease

• neonatal jaundice

elevated conjugated bilirubin means…

• hepatocellular disease → liver damage

• cholestasis → blockage to flow of bile

• decreased transport of conjugated bilirubin

acute liver disease is…

viral, toxic, due to alcohol consumption

liver inflammation

rapid onset

chronic liver disease is …

alcoholic hepatitis/cirrhosis, non-alcoholic steatohepatitis, autoimmune disorders, genetics

slow progression

causes of acute hepatitis

hep A, hep B, Hep C (viral)

Paracetamol (toxins)

causes of chronic hepatitis

ongoing hepatic necrosis & liver inflammation

ongoing over consumption of alcohol, some medications, recreational drugs

acute and chronic hepatitis change levels of:

• increased ALT (alanine aminotransferase)

• increased AST (aspartate aminotransferase)

• increased conjugated bilirubin

what is cholestasis

a blockage in the bile duct, meaning bile flow is obstructed into duodenum

results in bile (w/ conjugated bilirubin) is absorbed into the blood →obstructive jaundice

intrahepatic cholestasis

• structural liver tissue damage

• decreased bile flow in absence of overt bile duct obstruction

• accumulation of bile constituents in liver and blood

extrahepatic cholestasis

• bile duct obstruction, eg. gallstones, malignancies, pancreatitis

• increased ALP

• increased conjugated bilirubin

Alkaline Phosphatase (ALP) found where

• surface of hepatocyte

• microvilli of bile canaliculi

• ducts

Alkaline phosphatase (ALP) why would it be raised?

• cholestasis

• hepatic injury

• infiltrative diseases, w/ tumours

• growth spurts in adolescents

• broken bones