Chemical Pathology Flashcards
Egs of invasive prenatal screening
Amniocentesis
Chorionic villus sampling
Cordocentesis
Egs of non invasive prenatal screening
Ultrasound
Doppler studies
MRI
Maternal serum biochem
Tests done on amniotic fluid
Karyotyping
DNA
Biochem
Enzyme studies
Possible complications of amniocentesis
Miscarriage
Transient fluid leak
Intrauterine infection
When is amniocentesis done
15-18 weeks
Routes of chorionic villus sampling
Transcervical
Transabdominal
Test done on villus sample
Karyotyping
DNA
Enzyme analysis
Possible complications of chorionic villus sampling
Miscarriage
Bleeding
Infection
Limb defects
When is villus sampling done
8-13 weeks
Function of hCG
Stimulate corpus luteum to continue producing progesterone in early preg before placenta takes over.
What produces hCG
Syncytiotrophoblasts
What causes increase in hCG
Pregnancy
Trophoblastic disease
Ectopic pregnancy
Down’s syndrome
hCG alpha subunit common to..
TSH, FSH, LH
In hCG intermediate range 5-25 then..
Do serial measurements.
If more than double per day = viable
If not, do ultrasound = ectopic/ spontaneous abortion.
When is triple test done
15-23 weeks (in second trimester)
What is triple test
AFP, unconjugated oestriol e3, hCG
What is added for quad test
Dimeric inhibin A
Where is AFP produced
Fetal yolk sac then liver
Causes of increased AFP
NTD, abdo wall defect, fetal renal disease, oligohydramnios, multiple preg, fetal death, incorrect dates, tumour (HCC), duodenal/ oesophageal atresia.
Causes of AFP decrease
Down’s syndrome
Edward’s syndrome
What organs need to be functional to produce oestriol E3
Fetal adrenal, liver and placenta
Causes of oestriol E3 decrease
Fetal death
Disruption in synthetic pathway
Chromosome abnormality
What produces inhibin A
Placenta
Cause of increase inhibin A
Down’s syndrome
What is PAPP-A produced by
Placenta
What causes PAPP-A increase
Coronary artery syndrome
Early decrease in PAPP-A..
Down’s syndrome
When best to do AFP
16-18 weeks
What can be tested in cell free DNA
Sex (7 weeks)
Fetal RhD
Fx CSF
Support
Shock absorption
Transport of substances
What changes BBB permeability
Inflammation
Immaturity
Toxins
Neovascularisation (tumour, ischemia, trauma)
Protein CSF concentration influenced by..
Plasma concentration
BBB permeability
CSF flow (Froins, prolapse disk, abscess)
Multiple sclerosis
Markers for major depression
Decrease 5HIAA and serotonin
Defn xanthochromia
Visual diagnosis of bilirubin in CSF
Test done to confirm xanthochromia
NBA - nett bilirubin absorbance
NBA determines
Need for angiography
Causes of xanthochromia
SAH
Very high protein, increase serum bili, meningeal melanoma, hypercarotinaemia, rif therapy, previous traumatic tap.
Hypertension increases risk of..
Stroke, heart failure, MI, renal failure
What inhibits mineralocorticoid receptor
Spirinolactone
What inhibits ENa channel
Amiloride
Blood results in hyperaldosteronism
Hypernatraemia
Hypokalaemia
Alkalosis
Aldo:renin ratio in Conns
Increased
Tests done in Conns
Morning Aldo
Aldo:renin ratio
Saline loading
Part of adrenal secreting Aldo
Zona glomerulosa
Causes of increased cortisol
Pituitary adenoma
Adrenal tumour
Drugs
Ectopic Ca (eg bronchus)
Mechanism of cushing’s
Saturates 11BHSD
Binds mineralocorticoid receptor
Tests done in cushing’s
24hr urine Midnight cortisol (loss of diurnal rhythm) Low dose dexamethazone suppression test
Find cause = ACTH level (increase = ectopic)
How does liquorice increase BP
Inhibits 11BHSD causing cortisol to bind mineralocorticoid receptor
Where is the defect in Liddle syndrome
Beta subunit of ENaC
What syndrome is pheochromocytoma associated with
Multiple endocrine neoplasia
How does pheochromocytoma increase BP
Catecholamines cause vasoconstriction and increase cardiac output
Investigations done to diagnose pheochromocytoma
Serum catecholamines
Urine metanephrine / normetanephrine
How is pheochromocytoma localized
MIBG scan
(Radioactive adrenalin analogue)
What are the renin and Aldo levels like in renal artery stenosis
Renin increased
Aldo increased
Why are Na levels normal in renal artery stenosis
Angiotensin ll increases thirst and ADH which causes water retention - diluting hypernatraemia
How do water soluble agents cross the BBB?
Paracellular aqueous pathway (through tight junction)
How do lipid-soluble agents cross the BBB?
Trans cellular lipophillic pathway
How do glucose, amino acids and nucleosides cross the BBB?
Transport proteins
How do insulin and transferrin cross the BBB?
Receptor-mediated transcytosis
How does albumin and other plasma proteins cross the BBB?
Absorptive transcytosis
Where to stick needle in LP
Between L3 and L4
When is CSF lactate increased?
- cerebral hypoxia
- diffuse meningeal conditions
- certain IMDs
What is a good indicator of BBB permeability?
Albumin
When is CSF analysed spectrophotometrically
High clinical suspicion of SAH but negative CT scan
Clinical course of MS
Plaque, gliosis, chronic plaque with no myelin
Another name for B2 transferrin
Asialotransferrin
Biochemical markers of primary hyperaldosteronism
- blood k decreased
- urine potassium increased
- blood Na mildly increased
- blood metabolic acidosis
- blood renin decreased
- blood aldosterone increased
Define apparent mineralocorticoid excess
The presence of hypertension, increased Na and bicarb and decreased K
Suppressed renin
Low aldosterone levels
Causes of apparent mineralocorticoid excess
- Cushing’s syndrome
- excessive liquorice ingestion
- liddle’s syndrome
Metabolic derangements in alcohol abuse
- hypertriglyceridaemia
- hypoglycemia
- ketosis
- lactic acidosis
- hyperuricaemia
What does raised IgG imply?
Increased local intra theca production
Causes of raised IgG
- neurosyphilis
- multiple sclerosis
Type of inheritance of hemophilia B
X linked recessive
Causes of hypertension associated with hypokalaemia
- primary hyperaldosteronism
- secondary hyperaldosteronism
- Cushing’s
- renal artery stenosis
- apparent mineralocorticoid excess
Tests for phaeochromocytoma
- TSH
- metanephrines/ catecholamines
Causes of massively elevated CSF protein
- obstruction of CSF flow in the spine
- tumour
- abscess
- disc prolapse
What non- pregnant states cause abnormality in AFP?
Hepatocellular cancer
Germ cell tumours
