Biochemistry Flashcards
What is biochemistry?
- Measurement of concentration or activity of important biological substances in bodily fluids
- Measure ions and molecules
What are the positives of in house testing?
- Results same day
What are the positives of commercial lab testing?
- Can test wide range parameters
- Gold standard testing
- Cheaper per parameter
What are the negatives for in house testing?
- Equipment to buy
- Consumables to buy
- Staff training
- Staff time
- Not all parameters measurable
What are the negatives for commercial lab testing?
- Wait for result
- Abnormal results
What is the difference between plasma and serum?
- Plasma is from unclotted blood and serum is from clotted blood
When would you use an orange top tube (heparin anticoagulant)?
- Plasma
When would you use a white top tube (no anticoagulant)?
- Serum
When would you use a brown top tube (no anticoagulant, has gel)?
- Serum
What does biochemistry measure?
- Electrolytes
- Total protein
- Kidney parameters
- Liver parameters
- Pancreas parameters
- Hormones
- Other muscle and heart parameters
What are electrolytes in biochemistry?
- Major cations (sodium and potassium)
- Major anions (chloride and bicarbonate)
- Also measures calcium and phosphate
What do changes in sodium (cation) show?
- Increase: dehydration
- Decrease: over-hydration
What do changes in potassium (cation) show?
- Increase: Cell lysis, hypoadrenocorticism and renal insufficiency
- Decrease: Diabetic ketoacidosis
What do changes in bicarbonate (anion) show?
- Increase: alkalosis
- Decrease: acidosis
What do changes in calcium show?
- Increase: issues with parathyroid or neoplasia
What do changes in phosphate show?
- Increase: Diet or decrease in renal function
What does an increase of lactate show?
- Suggest lactic acidosis, which can show an issue with oxygen saturation in tissues
What does the liver make when metabolising?
- Protein
- Albumin
- Cholesterol
What happens when the liver detoxifies product?
- Converts ammonia into urea
- Excretes bilirubin into bile
When is liver function lost?
- When 70% of tissue is non-functional
How does liver damage occur via bile stasis/cholestasis?
- If bile not flowing due to inflammation/obstruction, ALP and GGT increase in blood
How does liver damage occur via cell death?
- ALT and AST get released whrn hepatocytes burst
What are the secondary factors that increase liver enzymes?
- Increase in corticosteroids/cushings disease
- Hyperthyroidism
- Daibetes mellitus
- Pancreatitis
- Obesity
- Starvation
- Various drugs
How does the liver function with the circulation of bile acids?
- 90% of bile acids reabsorbed from intestine and recycled by the liver
- If not functioning well, bile acids can’t be reabsorbed
- Biliary system needs to have free flow of bile or bile backs up into blood
What is a common liver damage test and what is it?
- Bile acid stimulation test
- Detects abnormal increase in bile acids; compare fasting blood sample and fed blood sample
What other levels can be tested to look for liver damage except bile acids?
- Bilirubin
- Albumin
- Glucose
- Clotting factors
- Ammonia
What is the function of the kidney?
- Excretes waste products such as urea, creatinine and SDMA
- Controls hydration
- Balance electrolytes
- Produces erythropoietin
What is the glomerular filtration rate?
- The volume of filtrate produced in the Bowman’s capsule in unit time
- Useful measure of kidney function
How can the glomerular filtration rate be measured?
- Inject a harmless, freely filtered chemical and measure how much remains in the blood overtime
- Estimate GFR using creatinine and SDMA, can stage CKD
How can the kidney be investigated?
- Look at GFR
- Increase in waste products in the blood
- Loss of ability to concentration urine, causing PUPD (when this happens 2/3 of renal function lost)
What does an increase in urea show?
- Alone, elevation unlikely to be a renal cause
- Related protein metabolism, so affected by diet and liver as well as the kidney
What does an increase in creatinine show?
- Alone, elevation unlikely to be renal cause, as creatinine increases at 75% loss of kidney function
- Muscle metabolism
What does an increase in SDMA show?
- Elevation suggests renal damage (elevate at 40% renal loss)
Why is creatinine isn’t great to estimate GFR?
- When there is a large change in GFR, there is a little change in creatinine levels in early renal disease and vice versa in advanced renal failure
What is azotaemia?
- Abnormal increase in concentrations of non-protein nitrogenous wastes in blood
What is uraemia?
- Adverse clinical signs due to severe azotaemia
What are the clinical signs in the pre-renal stage?
- Low volume and very concentrated urine
- Dehydration
- Hypovolaemia
What are the clinical signs of renal stage?
- Dilute, large volume urine that may contain protein
- PUPD
- Hypertension
- Anaemia
What are the clinical signs at post-renal stage?
- No urine if urethra blocked, concentrated, may contain blood
- Dysuria
What are the pre-renal insufficiency factors?
- Dehydration
- Cardiac failure
- Haemorrhage
What are the renal insufficiency factors?
- Toxins
- Infections
- Crystals
- Cysts
What are the post-renal insufficiency factors?
- Stone
- Tumour
- Prostate affecting ureter/bladder/urethra
What are other renal disease tests other than examination of waste product levels?
- Ultrasonography
- Radiography
- Blood pressure assessment
- Proteinuria
- Urine specific gravity
What are the two types of dynamic tests?
- Stimulation test
- Suppression test
What do stimulation tests do?
- Gives exogenous form of stimulating hormone and measures level of hormone in response; should expect an increase
What do suppression tests do?
- Gives exogenous form of hormone and measures level of endogenous hormone in response; should expect a decrease
What are the thyroid hormones?
- T3: active form
- T4: thyroid secretes most as T4
What do thyroid hormones do?
- Increases metabolic rate
- Helps cope with period of low-calorie intake by increasing blood glucose and use of body fat and body protein
- Increases heart rate and force
- Affects NT’s in brain and mood
What is the thyroid disease in dogs?
- Hypothyroidism
- Immune destruction or caused by a chronic illness which decreases T4 levels
- Increases cholesterol and triglycerides
What is the thyroid disease in cats?
- Hyperthyroidism
- Thyroid hyperplasia or caused by thyroid tumour
- Increases T4 levels
- Causes liver and kidney damage
What does cortisol do in the adrenal cortex?
- Increases blood glucose
- Anti-inflammatory
- Decreases immunity
- Controlled by ACTH
What does aldosterone do in the adrenal cortex?
- Increases blood sodium and BP
- Decreases potassium
- Controlled by RAAS, an increase in potassium and ACTH
What happens in hyperadrenocorticism/hypercortisolism (Cushing’s disease)?
- Protein breakdown
- Increased blood glucose
- Lipid and calcium breakdown and redistribution
- Increases BP
What are the clinical signs of hyperadrenocorticism/hypercortisolism (Cushing’s disease)?
- Alopecia
- PUPD
- Decreased inflammatory and immune responses
What are the causes of Cushing’s disease?
- Pituitary tumour
- Adrenal gland tumour
- Treatment with corticosteroids
What are the biochem, haematoloy and urinalysis findings of a Cushing’s disease patient?
- Increased liver enzymes
- Hyperglycaemia
- Increased triglycerides and cholesterol
- Dilute urine
- Neutrophilia
What is the ACTH stimulation test and what results should be expected?
- Administration of exogenous adrenocorticotropic hormone IV or IM and measure the effect on cortisol production
- Cushings = normally high pre and post
- Iatrogneic cushings = low pre and post
What happens in Hypoadrenocorticism (Addison’s disease)?
- Decreased aldosterone and/or cortisol
What are the biochem, haematology and urinalysis findings in an Addison’s patient?
- Increased potassium
- Decreased sodium
- Dehydration
- Urine concentrated
What are the functions of the pancreas?
- Endocrine: releases insulin
- Exocrine: releases lipase, amylase and trypsin
What happens in an endocrine pancreatic disease (diabetes mellitus)?
- Elevated glucose and possibly ketones in blood and urine
- Liver damage
- Elevated urea if dehydrated
- Use glucose curve or CGM
What is a continuous glucose monitor (CGM)?
- Measures glucose in interstitial tissue
- Slight delay (5-10min) compared with blood glucose curve
- Monitor 24 hours for 2 weeks
What are the reproductive hormones?
- Testosterone and oestrogen
- Progesterone
- Relaxin
What are the effects of haemolysis?
- False reduction in bilirubin
What is icterus (jaundice) caused by?
- Caused by an increase production of bilirubin from haemolysis
- A decrease in excretion of bilirubin from liver disease or cholestasis
What is lipaemia (fatty blood)?
- Excess fat in blood plasma; centrifuged sample looks creamy
- Caused by hyperlipidaemia
- Causes haemolysis
What does contamination from the K EDTA blood tube cause?
- Biochem contaminated from K EDTA can cause reduced calcium, increased potassium and decreased ALP and ALT
What can fear stress cause on blood results?
- Hyperglycaemia due to adrenaline and cortisol
- Triglycerides, cholesterol, and liver enzymes increase from cortisol
When may you need to fast before a blood sample?
- If measuring urea, glucose, triglycerides, cholesterol, pancreatic enzymes, bile acids and liver enzymes
