Chemical Pathology Flashcards by Michael Nel

Egs of invasive prenatal screening

Amniocentesis
Chorionic villus sampling
Cordocentesis

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Egs of non invasive prenatal screening

Ultrasound
Doppler studies
MRI
Maternal serum biochem

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Tests done on amniotic fluid

Karyotyping
DNA
Biochem
Enzyme studies

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Possible complications of amniocentesis

Miscarriage
Transient fluid leak
Intrauterine infection

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When is amniocentesis done

15-18 weeks

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Routes of chorionic villus sampling

Transcervical

Transabdominal

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Test done on villus sample

Karyotyping
DNA
Enzyme analysis

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Possible complications of chorionic villus sampling

Miscarriage
Bleeding
Infection
Limb defects

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When is villus sampling done

8-13 weeks

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Function of hCG

Stimulate corpus luteum to continue producing progesterone in early preg before placenta takes over.

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What produces hCG

Syncytiotrophoblasts

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What causes increase in hCG

Pregnancy
Trophoblastic disease
Ectopic pregnancy
Down’s syndrome

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hCG alpha subunit common to..

TSH, FSH, LH

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In hCG intermediate range 5-25 then..

Do serial measurements.
If more than double per day = viable
If not, do ultrasound = ectopic/ spontaneous abortion.

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When is triple test done

15-23 weeks (in second trimester)

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What is triple test

AFP, unconjugated oestriol e3, hCG

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What is added for quad test

Dimeric inhibin A

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Where is AFP produced

Fetal yolk sac then liver

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Causes of increased AFP

NTD, abdo wall defect, fetal renal disease, oligohydramnios, multiple preg, fetal death, incorrect dates, tumour (HCC), duodenal/ oesophageal atresia.

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Causes of AFP decrease

Down’s syndrome

Edward’s syndrome

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What organs need to be functional to produce oestriol E3

Fetal adrenal, liver and placenta

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Causes of oestriol E3 decrease

Fetal death
Disruption in synthetic pathway
Chromosome abnormality

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What produces inhibin A

Placenta

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Cause of increase inhibin A

Down’s syndrome

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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

Chemical Pathology Flashcards

(77 cards)