Laboratory Methods

Question 1

Array CGH

Answer 1

Compare control DNA to Case DNA
Good at spotting small differences
Detects changes in length (deletions, duplications)
e.g. uniparental disomy

Question 2

Chromosome numerical abnormalities

Answer 2

Missing whole chromosome e.g. Turners (missing X = XO)

Extra whole chromosome e.g. Trisomy 21 (non disjunction)

Question 3

Karyotyping

Time taken
Type of dye
Shows what?

Answer 3

Requires waiting to observe cell cycle - can only see chromosomes at division (takes 1-2 weeks)

Giesma staining
Can see large structures and arrangements
e.g. Trisomy 13,18,21, ring chromosomes

Question 4

FISH

Answer 4

Rapid
Identifies aneuploidies
Now we do Array CGH instead

Fluorescence in situ hybridisation

Question 5

Quantitative fluorescent PCR

Answer 5

Quick aneuploidy detection
Pre-natal testing
Checks for short tandem repeats

Question 6

Anion Gap - needed to calculate

Answer 6

Sodium
Potassium
Chloride
Bicarb

Question 7

Anion Gap

Answer 7

(Na + K) - (Cl + HC03)
Normal between 10-16

Question 8

Unmeasured anions

Answer 8

Organic acids
Inorganic acids
Proteins

Caluculating anion gap can point to disorders associated with these e.g. Maple syrup urine disease

Question 9

Pseudohyponatremia

Answer 9

High glucose makes serum sodium appear falsely low e.g. in DKA due to osmotic shift
Hyperlipidaemia also

Question 10

Pre-renal failure

Answer 10

Body holds onto sodium
Not got enough volume
Low excretion of sodium

Question 11

Tubular damage

Answer 11

Unable to reabsorb
Sodium losses

Question 12

Extrinsic Pathway test

Answer 12

High PT, normal APTT

Warfarin treatment
Factor 7 deficiency

Question 13

Intrinsic pathway test

Answer 13

High ATPP, normal PT

Haemophilia A/B
Factor 11 + 12 deficiency
VW disease
Heparin treatment

Question 14

Common Pathway test

Answer 14

High PT + High APTT

Factor 2, 5 or 10 def
Fibrinogen def
Vit K def
DIC

Question 15

ITP test

Answer 15

ATPP + PT normal
FBC - platelets

Question 16

Vitamin K dependent factors

Answer 16

2, 7 ,9, 10

Question 17

Factor II

Answer 17

Thrombin

Question 18

Extrinsic pathway

Answer 18

Tissue factor
Factor 7 (VII)
Factor 7a (VIIa)
Leads to activation of factor 10 (X)

Question 19

Common pathway

Answer 19

Leads to formation of Fibrin from thrombin

Factor Xa + Factor V changes prothrombin to thrombin
Thrombin converts Fibrinogen into fibrin
Thrombin acts on intrinsic pathway

Question 20

Intrinsic pathway

Answer 20

Mediated by Kallilkrein
Factor 12
Factor 11
Factor 9
Factor 8
Factor 10 (activates common pathway)

Question 21

Heparin and Fondaparinux

Answer 21

Enhance effect of antithrombin
Inhibits thrombin and factor Xa

Question 22

Factor 1

Answer 22

Fibrinogen

Question 23

Factor 3

Answer 23

Tissue factor

Question 24

Factor 4

Answer 24

Ionized calcium (Ca2+)