Clinical Chemistry Flashcards
What does haemocrit level tell us?
The % of the whole blood that is made up of RBCs
E.g. Raised in dehydration
What may cause an increase in RBCs due to decreased oxygen supply to the kidneys (which produce EPO) ?
- smoking
- altitude
- COPD
- blood loss
What is ESR a marker of ?
- inflammation
- anaemia
- cancer
- the higher the ESR the worse the disease/inflammation
What blood markers are included in the inflammation triad?
CRP, ESR and plasma viscosity
ALP levels can indicate damage where ?
Biliary tree
ALT, AST, GGT give info from where in the liver ?
Inside the liver
What can be measured in the blood to give information about pre hepatic problems ?
Bilirubin
What does the ratio of indirect bilirubin:direct bilirubin tell us
Evaluate liver plumbing and performance
Reasons for low albumin?
- nutritional problems
- protein loss through renal disease
- failure of protein synthesis due to loss of functioning liver tissue
- inflammatory conditions (liver switches to maki diff proteins)
What do alanine aminotransferase (ALT) and aspartate aminotransferase (AST) indicate ?
- indicate leakage from damaged cells due to inflammation or cell death
- normally inside cells so raised levels indicates hepatocellular damage
Which is more specific to the liver AST or ALT ?
ALT
* AST also found in cardiac and skeletal muscle and RBCs
Which other measurement can help localise source of raised transferases ?
- Creatinine kinase (CK), raised will confirm muscle damage
- troponin will confirm myocardium damage
*liver more likely if both AST and ALT are raised
Which rises more in acute liver damage, ALT or AST ?
ALT
- very high levels suggest drug toxicity or viral or autoimme hepatitis
Once cirrhosis is established in liver disease what is the AST:ALT ratio ?
AST>ALT
AST:ALT ratio >2 suggests what ?
Alcoholic liver disease
Raised GGT in patient with chronic liver disease is associated with what ?
Bile duct damage and fibrosis
Where does alkaline phosphatase (ALP) come from ?
- Cells lining the bile ducts
- bone
Raised ALP and normal GGT suggests what ?
Bone disorders
What test is useful in distinguishing alcoholic and non alcoholic fatty liver disease ?
AST:ALT ratio
>2 = alcoholic
Causes for raised unconjugated bilirubin
- increased bilirubin production (e.g. Haemolysis)
- decreased hepatic uptake or conjugation or both
Causes of conjugated hyperbilirubinaemia
- liver disease
- cholestatic drug reactions
- immune cholestatic disease
- biliary obstruction
Raised bilirubin with raised ALP and GGT higher than rise in aminotransferases suggests what ?
- Biliary Obstruction
- cholestatic disease
- liver injury with cholestatic pattern (less common)
Isolated rise in GGT suggests what ?
- Alcohol abuse
- enzyme inducing drugs
Varying degrees of ALP In those with ulcerative colitis suggests what ?
Primary sclerosing Cholangitis
Raised ALP in middle aged women with history of pruritis and autoimmune disease is suspicious of what ?
Primary biliary cirrhosis
Elevated GGT, MCV very high and very low folate suggests what ?
Excessive alcohol intake
High GFR has what result on sodium loss ?
Increased sodium loss
Causes of hypernatraemia
- hyperaldosteronism
- diarrhoea and vomiting,dehydration(fluid loss without replacement)
- diabetes insipidus
- iatrogenic e.g. Incorrect IV fluid replacement
Presentation of hypernatraemia ?
- thirst, polydipsia, polyuria
- CNS dysfunction: lethargy, weakness, confusion, Irritability, seizure
- dehydration + hypovolaemia: dry mouth, abnormal skin turgor, tachycardia etc
Symptoms of hyponatraemia
Mild: anorexia, headache, vom, lethargy
Mod: personality change, muscle cramps, weakness, confusion. Ataxia
Severe: drowsiness
Causes of hyponatraemia ?
- SIADH
- diuretics
- renal failure
- vom/diarrhoea
- sweat, burns
Causes of hyperkalaemia ?
- renal: AKI, CKD,
- Mineralocorticoid deficiency
- rhabdomyolysis
- drugs
- DKA
Drugs that can cause hyperkalaemia ?
- ciclosporin
- tacrolimus
- pentamidine
- ketoconaole
- NSAIDS
- Spironolactone
Signs of hyperkalaemia
- muscle weakness and flaccid paralysis
- depressed/absent tendon reflexes
- tall tented t waves, small p waves and wide QRS on ECG
- arrhythmias, palpitations, fast irregular pulse, chest pain
Interpret ABG:
- pH: 7.05
- CO2: 2.0kPa
- HCO3: 8.0 mmol/L
Metabolic acidosis:
There is an acidosis as pH
Causes of metabolic acidosis ?
- lactic acid
- urate (renal failure)
- ketones
- Addison’s
- diarrhoea
- drugs
Causes of metabolic alkalosis ?.
- vomiting
- burns
- ingestion if base
- potassium depletion e.g. Spironolactone
Causes of respiratory acidosis ?
- type 2 resp failure e.g. COPD
Causes of resp alkalosis
- hyperventilation
- mild/mod asthma
- PE
- drugs
- stroke
Signs and symptoms of hypokalaemia
- muscle weakness
- hypotonia
- hyporeflexia
- cramps
- tetany
- small/inverted t waves, prominent u wave , long PR, depressed ST
Causes of hypokalaemia
- diuretics
- vomiting and diarrhoea
- alkalosis
- Cushing’s
- Conns syndrome
Overall affect of PTH on calcium and phosphate ?
Increase calcium and decrease phosphate
How does PTH control calcium and phosphate levels ?
- Secretion of PTH triggered by low serum levels of ionised calcium
- PTH causes increased osteoclast activity, releasing Ca and PO from bones
- causes increased Ca and decreased PO reabsorption in kidney
- increasing renal production of D3
Where is vitamin D turned in to its active form?
Kidney
1,25-dihydroxy vit D aka calcitriol
What stimulates calcitriol production ?
- Low calcium and phosphate
- PTH
What are the actions of calcitriol?
- increased calcium and phosphate absorption from gut
- inhibits PTH release
- enhanced bone turnover
- increased calcium and phosphate reabsorption from kidneys
What is cholecalciferol?
D3 from animal source
What is ergocalciferol?
D2 from vegetables
What is calcitonin ?
Made in C cells of thyroid- causes decreased calcium and phosphate
- marker for recurrence/metastasis in medullary carcinoma of thyroid
How might magnesium cause hypocalcaemia
Low levels of magnesium prevent the release of PTH (which increases levels of calcium)
Symptoms of hypercalcaemia
bones, stones, groans, psychic moans, sitting on the throne
- bone pain
- renal calculi
- abdo pain, nausea and vomiting
- depression, anxiety, insomnia
- polyuria, constipation
Signs and symptoms of hypocalcaemia?
- cramps
- perioral numbness
- carpopedal spasm (trousseaus sign)
- tetany
- chvosteks sign
What does the mean cell volume (MCV) tell us?
What size are the RBCs e.g. Macrocytic?
