chemical pathology

Question 1

what does fever usually correspond to

Answer 1

temperature increase due to infection

Question 2

cause of fever, rash, lymphadenopathy

Answer 2

viral illness (e.g. glandular fever)

Question 3

causes of diarrhoea

Answer 3

virus, bacteria, parasites

Question 4

GP: what is FBC test

Answer 4

full blood count

Question 5

GP: what is ESR test

Answer 5

erythrocyte sedimentation rate; if lots of inflammatory proteins and white cells, settle faster - something’s wrong (usually infection)

Question 6

GP: what is CRP test

Answer 6

C-reactive protein (protein made by liver when infection) - marker

Question 7

hospital: what are LFTs

Answer 7

liver function tests (if liver is damaged, enzymes released into bloodstream)

Question 8

hospital: enzymes in LFT which would show physical blocking of bile

Answer 8

high level of alkaline phosphatase and low AST

Question 9

hospital: what is U and E

Answer 9

urea and electrolytes

Question 10

hospital: other test

Answer 10

blood glucose

Question 11

GP: other tests

Answer 11

lx of viral illness, stool culture (bacteriology)

Question 12

how to request tests

Answer 12

tick relevant tests for diagnosis on clinical chemistry form e.g. U&E, liver, glucose

Question 13

3 things when collecting blood

Answer 13

correct tube, correct patient (ask them for name), label tube with patient’s details (if urgent ensure gets to lab in time)

Question 14

4 tubes and anticoagulants

Answer 14

red top: none; yellow top: gel to speed up clot; purple top: K+ EDTA (keeps cells alive); grey top; fluoride oxalate (poison to ensure red cells don’t perform glycolysis - important in diabetics to measure glucose)

Question 15

sample collection tubes: U&E

Answer 15

serum in yellow/red top

Question 16

sample collection tubes: glucose

Answer 16

plasma in grey top

Question 17

sample collection tubes: HbA1c (long term marker of blood glucose as glycated Hb - useful in diabetics; marker of tissue damage in heart and other tissues)

Answer 17

plasma in purple top

Question 18

sample collection tubes: thyroid function test

Answer 18

serum in yellow/red top

Question 19

sample collection tubes: liver function tests

Answer 19

yellow/red top

Question 20

what is serum (e.g. U&E serum in yellow/red top)

Answer 20

no anticoagulant, so sample clots (using up all clotting factors), which are then removed

Question 21

2 anticoagulants

Answer 21

EDTA, heparin

Question 22

what happens to blood if anticoagulants added

Answer 22

clotting factors unused so blood can be separated into red cells and plasma by centrifuge

Question 23

plasma vs serum

Answer 23

plasma contains clotting factors, serum doesn’t

Question 24

how is glucose measured in blood

Answer 24

red cells consume glucose (anaerobic glycolysis), so longer left, lower glucose; fluoride oxalate (poison) prevents red cells from using glucose

Question 25

role of chemical pathologists

Answer 25

in charge of labs, research into better methods of getting results, do metabolic medicine clinics, do some tests

Question 26

when do you contact chemical pathologist

Answer 26

when you want sample to be rapidly centrifuged out of hours (separate out red cells to leave plasma/serum), when you want to measure labile hormones e.g. insulin, when urgently need CSF glucose and protein to be measured (high protein, low glucose indicates bacteria in CSF)

Question 27

where are results available from

Answer 27

computer, and if urgent results phoned to requesting clinician

Question 28

how is reference range determined, and where are they given

Answer 28

looks at normal people, measure data and take highest and lowest; given next to value

Question 29

potential cause of low Na+ and high K+

Answer 29

adrenal failure (loss of aldosterone);

Question 30

haemolysis contributing to high K+ reading, and how to know if haemolysis

Answer 30

red cells burst as come through needle, releasing K+; also releases Hb, so plasma when centrifuged appears rose - K+ result given as "haemolysed"

Question 31

markers for renal function

Answer 31

Na+, K+. urea, creatinine

Question 32

what happes to [urea] and [creatinine] if renal failure

Answer 32

both rise

Question 33

what does it show if urea goes up but creatinine doesn't

Answer 33

GFR fine, but tubules absorbing more water; very dehydrated (if kidney damage, both go up)

Question 34

what is creatinine a marker of

Answer 34

GFR (very little absorbed or secreted by tubules)

Question 35

when happens in dehydration

Answer 35

urea rises, but GFR stays same

Question 36

liver enzymes

Answer 36

tiny amount leaks into blood, but more in liver disease

Question 37

what to measure besides "liver" in jaundice patients

Answer 37

AST, GGT

Question 38

liver enzymes and when increased

Answer 38

albumin (synthesised in liver), bilirubin (block of bile duct so enters bloodstream), alkaline phosphatase, ALT (alanine amino-transferase - increase when liver inflamed e.g. viral hepatitis) MORE

Question 39

what does high bilirubin indicate

Answer 39

indictaes jaundice; albumin low, bilirubin high, alkaline phosphatase high, ALT and AST high MORE

Question 40

making diagnosis

Answer 40

ask patient what is wrong -> take history -> examine -> make plan (tests)

Question 41

cardiac enzymes when heart muscle damaged, and what it can show

Answer 41

heart muscle, and leak into blood in large amounts when heart muscle damaged, can tell if someone had a heart attack

Question 42

4 cardiac enzymes

Answer 42

troponins, creatine kinase, aspartate amino transferase (same as liver), lactate dehydrogenase

Question 43

can tell by pattern of enzymes when heart attack occured

Answer 43

troponine and AAT up first, then creatine kinase, then lactate dehydrogenase