Chem Path Flashcards
0
Q
Interpretation of grey zone of PSA
A
- 4-10
- prostate carcinoma possible
- benign conditions also cause elevations
- should consider prostate biopsy
1
Q
The physiological role of PSA
A
Liquifies seminal coagulum after intercourse, allowing sperm mobility
2
Q
Benign causes for elevated PSA
A
- prostatitis
- BPH
- urinary retention
- catheterization
- cycling
- prostatic biopsy
3
Q
Iron- related acute phase reactants - direction of change during inflam
A
Transferrin - decreased
Ferritin - increased
4
Q
Test used in presence of inflam to identify iron deficiency anaemia
A
Soluble transferrin receptors
5
Q
Relevance of excessive tea drinking
A
- tea rich in tannins binds elemental iron in bowel lumen (preventing absorption)
6
Q
Biochem and haematological markers of iron deficiency
A
- low plasma iron
- increased plasma transferrin
- very low % saturation
- low plasma ferritin
- decreased Hb
- microcytosis (decreased MCV)
- low MCHC
- hypo chromic microcytic cells on microscopy
7
Q
Tests to distinguish acute iron poisoning from chronic overload
A
- ferritin normal in acute, high in chronic overload
- transferrin normal in acute, low in chronic overload
8
Q
Reason for increase in serum PSA 3 months after surgical prostate removal
A
Tumour recurrence/ metastasis
9
Q
Significance of raised ALP with normal GGT in prostate cancer
A
Bone metastasis - increased osteoblast activity
10
Q
Diagnostic value of serum free PSA estimation
A
- when total PSA is in grey zone! the higher the serum free PSA, the less likely Ca prostate
- because PSA secreted directly into blood is 100% bound to anti-chymotrypsin, but when PSA gains access via seminal vesicle (as per normal) a significant fraction is modified to no longer bind to anti-chymotrypsin and circulates in a free state
11
Q
Why castration is option for inoperable prostate cancer
A
- prostate cancer is often testosterone dependent
- removes major source of endogenous testosterone
12
Q
An absolute contraindication for testosterone replacement in elderly hypo gonadal males
A
- history of prostate cancer or raised PSA
- prostate cancer growth stimulated by testosterone
13
Q
Lab tests to distinguish thalassemia from iron deficiency anaemia
A
- serum iron
- transferrin
- ferritin
14
Q
Why paracetamol selectively damages the liver
A
Metabolized via cytP450 to a reactive intermediate (NAPQI)
- targets free sulphydryl groups on intracellular proteins
15
Q
Function of transferrin
A
Transports iron in circulation
16
Q
Conditions with low transferrin
A
- protein loss
- liver disease
17
Q
Why not treat anaemia empirically
A
Prevent iron over load in non-iron deficient disorders (thalassemia)
18
Q
Causes of raised INR
A
- liver disease
- vit k deficiency
- warfarin
19
Q
Why urea may be a misleading marker of renal function
A
Liver produces urea from ammonia
In liver failure, urea level may be lower than expected
20
Q
Disorders in which excessive urobilinogen in urine
A
- intra vascular haemolysis : lactate dehydrogenase
- hepatitis : transaminases
21
Q
findings in a space-occupying mass within the liver
A
- elevated ALP and GGT
- absence of jaundice
22
Q
When would you find an elevated GGT on its own
A
Alcohol abuse, chronic drug ingestion
23
Q
Useful biochemical tests for liver failure
A
- plasma ammonia
- abnormal INR
- hypoglycemia
- lactic acidosis
24
Clinical significance of bilirubin in urine
Obstruction to bile flow
25
Clinical significance of urobilinogen in urine
Haemolysis or intrinsic liver disease
26
Origin of ammonia in the body
Protein breakdown
27
What causes acute phase response
Any acute stress involving tissue necrosis
| - cytokines relay to brain and live
28
Positive acute phase reactants
- CRP
- a1 antitrypsin
- fibrinogen
29
Negative acute phase reactants
- albumin
- transferrin
- HDL
- LDL
30
Mechanism of lactic acidosis
- hypoxia to any tissue disrupts mitochondrial metabolism
- pyruvate metabolism not possible
- LDH forms lactic acid
31
Causes of pre-renal failure
- hypovolaemia
- decrease cardiac output
- renovascular obstruction
32
Causes of intra renal failure
- acute tubular necrosis
- acute glomerular nephritis
- interstitial nephritis
- intra renal vasoconstriction
- tubular obstruction
33
Causes of post renal failure
- bilat ureteric obstruction
| - urethral obstruction
34
Why urgent to decide between pre and intra renal
- pre can progress rapidly to more serious intra renal failure
- some treatment options for intra are opposite to pre
35
When to dialyse a patient
- volume overloaded at risk of pulm oedema or cardiac failure
- blood urea >50 and rising
- K high/ECG changes
- bicarb lower than 10
36
Definition of a buffer
Solution of conjugate acid-base pair
37
Causes of resp acidosis
- depression of resp centre
- physical inability to ventilate
- airway obstruction
- pulm disease causing decreased exchange
38
Causes of resp alkalosis
- direct stim of resp centre
- mech over ventilation
- hypoxia
39
Causes of metabolic acidosis
- gain of H
| - loss of bicarb (anion gap normal)
40
Causes of metabolic alkalosis
- gain of bicarb
| - loss of H
41
Requirements before a fasted lipid profile can be done
- stable diet for more than 2 weeks
- alcohol abstinence for 48hrs
- fast overnight
- sit for 5 mins before venesection (min tourniquet time)
42
Reasons for raised anion gap
- alcohol
- uraemia
- diabetic ketoacidosis
- drugs
- lactate
43
Requirements for reliable blood gas result
- arterial blood
- anticoag with heparin
- taken and kept anaerobic
- on ice
- analysed ASAP
44
AMI markers
- myoglobin (stores O2)
- creatine kinase (stores energy as creatine kinase)
A
- troponin (part of contractile apparatus)
45
Acquired causes of hypercholsterolaemia
- hypothyroidism
- nephrotic syndrome
- diabetes mellitus
46
Role of DMT1
Transports iron from gut into cell in reduced form
47
Role of ferroportin
Transports iron out of cell
| - inhibited by hepcidin
48
Role of hephaestin
- copper-containing protein on basolateral membr of gut cells
- oxidizes iron to Fe3 so it can be transported by transferrin
49
Role of caeruloplasmin
- copper-containing protein in circulation (macs)
| - oxidizes iron to fe3 so it can be transported by transferrin
50
Role of transferrin
Transporter of 2x Fe3 atoms in the blood
- normally 30% sat
- synthesised by liver
51
Role of transferrin receptors
- bind iron bound transferrin and internalises transferrin
| - increases with iron demand
52
Role of hepcidin
Inhibits ferroportin leading to
- accumulation of iron in RES and liver
- decreased iron uptake by GIT
53
Treatment if acute iron toxicity
- resuscitation
| - chelation with desferrioxanine
54
Description of hereditary haemochromatosis
- mutation in HFE protein leads to decrease in hepcidin synthesis
- iron stores accumulate in parenchyma
55
Cells affected first by folate deficiency
- blood cell precursors in BM
- mucosal cells of intestine
- rapidly growing fetus
56
People at risk for folate deficiency
- intestinal disease (malabsorption)
- pregnant women
- patients on anti-folate chemotherapeuric drugs
57
SAM needed for
- synthesis of neurotransmitters like ACh
| - synthesis of phospholipids used to make myelin
58
Biochem reactions for which vit b12 is an essential cofactor
- methionine synthase
| - methylmalonyl mutate (krebs cycle)
59
How to diagnose b12 deficiency
- elevated total homocysteine
| - elevated urinary methylmalonic acid
60
Causes of intra vascular haemolysis
- autoimmune
- mechanical (heart valves)
- infectious (malaria)
- inherited red cell fragility
- osmotic
61
Signs of intravascular haemolysis
- increase unconjugated BR
- increased conj BR and urobilinogen in urine
- increased LDH and AST in plasma
- decreased haptoglobin
- schistocytes on peripheral blood smear
- haemoglobinuria
62
How to know it's not intravascular but extra vascular haemolysis
- no increased unconjugated BR
| - often raised potassium
63
How to prevent extravascular haemolysis
- avoid tiny needles
- avoid high vacuum
- avoid drawing blood rapidly through long thin lines
64
2 types of porphyria
- porphyrinogens spontaneously oxidized to porphyrins (reactive to UV, oxygen radicals damage skin)
- massive build up of PBG and dALA (mimic neurotransmitters - acute attacks)
65
Things that can trigger acute porphyria attacks
- onset of puberty
- fasting carb depletion
- drugs and alcohol
66
Characteristics of an acute attack
- abdo pain
- sensory and motor neuropathy
- autonomic neuropathy
- CNS (anxiety)
- hyponatraemia (vomiting)
67
Management of acute attack
- make diagnosis (PBG and ALA in urine)
- don't operate
- push glucose
- ascertain fluid balance and slowly correct hyponatraemia
- get expert advice
- get into ICU and ventilate
68
Screening test for acute attack of porphyria
- 1ml freshly voided urine
- add 1ml Erlich's aldehyde
- mix
- pink/red color implies presence of urobilinogen
- add 2ml chloroform
- mix and allow to settle
- PBG remains in top layer
69
PSA measurement good for
- progression of tumour
- response to therapy
- screening
70
Things to measure to improve PSA specificity
- PSA density
- PSA velocity
- % free
- complexed PSA
71
Characteristics of a good tumour marker
- normally absent
- no false positives (specific) and no false negatives (sensitive)
- long time before clinical presentation
- specific for particular tumour
- correlates with tumour mass and stage
- prognostic value
- easily measured
- treatment exists
72
Important considerations when assessing pituitary function
- negative feedback
- cyclical fluctuations
- effect of stress
- effect of intense exercise
- effect of development
73
Major actions of growth hormone
- antagonists insulin (promotes lipolysis)
| - stimulates production of insulin like GH1 (inhibits protein breakdown)
