Blood Tests

Question 1

plasma vs serum

Answer 1

serum is formed when blood is allowed to coagulate
plasma is the separated fraction from uncoagulated blood

Question 2

contents of plasma

Answer 2

water
electrolytes
waste products - urea, creatinine
bilirubin
enzymes from muscle or liver - alanine transaminase, alkaline phosphotase from liver, bone, placenta),
proteins (immunoglobulins, albumin (major circulating proteins at 40g/l)

Question 3

when whole blood is centrifuged, the layers are____

Answer 3

erthyrocytes at bottom, then white then platelets then serum/plasma

Question 4

thromboxane, ADP level and other things need to be measured in _____ because ______

Answer 4

plasma because they are formed during the coagulation process

Question 5

to create plasma inhibit coagulation by

Answer 5

• add edta (calcium collator)
• oxalic acid / oxalate
• add heparin
• fluorimide - fluoride inhibits lots of enzymes systems → stop ex vivo glucose metabolism

Question 6

for a red blood count blood should not coagulate because _____

Answer 6

when blood coagulates fibrin forms fibrinogen so rbc, white, platelets cant be counted

Question 7

categories of blood test

Answer 7

1. clinical biochemistry
   urea and electrolytes, LFT, immunoglobulins, calcium and phosphate, glucose, hba1c
2. microbiology
   serology for syphilis, bacterial RNA (blood culture)
   whole blood added to culture medium - see if microorganisms grow
3. immunology
   autoantibody screens
4. virology
   CMV, viral assay measuring RNA, DNA, serology. CMV IgG should be positive in most people - would have had it (more severe in adulthood)
5. haemotology
   FBC, bone marrow

Question 8

low serum sodium

Answer 8

hyponatremia - cirrhosis, inappropriate ADH secretion e.g., lung cancer

excess water

addisons, thiazide diuretics

Question 9

low serum potassium

Answer 9

diuretics, diarrhoea, mineralocorticoid excess (aldosterone)

low potassium with high BP = endocrine disorder e.g., cushings

Question 10

high serum potassium

Answer 10

acute kidney injury, spironolactone

Question 11

formation of urea

Answer 11

breakdown product of proteins

Question 12

low urea

Answer 12

alcohol

Question 13

high urea normal creatinine

Answer 13

dehydration

Question 14

low MCV

Answer 14

iron deficiency anaemia

Question 15

normal MCV

Answer 15

chronic disease

Question 16

high MCV

Answer 16

haemolysis
b12/folate deficiency anaemia
alcohol misuse

Question 17

elevated platelets

Answer 17

thrombocytosis

Question 18

low platelets

Answer 18

consumption in spleen

Question 19

low serum iron

Answer 19

chronic disease

not always anaemia - use ferritin and iron conc saturation

Question 20

hypothyroidism

Answer 20

low t4 high tsh

Question 21

hyperthyroidism

Answer 21

high t4