For analytes, such as glucose and cholesterol, patients need to be __ for at least 12 hours prior to veni-puncture.
fasting (absence of food and liquids)
For analytes, such as cortisol and adrenocorticotropin, have _ _, where the analyte is at its__ level in the morning, and the levels gradually ___ during the course of the day.
diurnal variations
highest
decrease
Correct procedure when using a tourniquet. & consequence if not done correctly.
• 3-4 inches above venipuncture site
• used no longer than 2 min
• release tourniquet before withdrawing needle
x If 2+ min = inc. K+ bc haemolysis, inc lactic acid
What happens if the alcohol @ the site of venipuncture is not completely dried?
Contaminate the sample = Haemolysis
IN order which veins is best to collect blood from?
- Median cubital vein
- Cephalic vein
- Basilic vein
What can excessive probing do to the sample?
haemolysis = inc K+
Phlebotomy order of draw (colour of top) [4]
1st: blood culture bottle/tube (Yellow / y-black)
2nd: coagulation tube (light blue)
3rd: non-additive tube (red) - just blood
4th: additive tubes
Phlebotomy order of draw (colour of top) FOR ADDITIVES TUBES [5]
a) SST (red-grey / gold) - has gel separator & clot activator
b) Sodium heparin (dark green) -> collect plasma
c) PST (light green) - has Li heparin anti-coag. & gel separator -> collect plasma
d) EDTA (lavender)
e) Oxalate/fluoride (light grey) or other addatives
What cases cause pseudohyperkalemia?
- Sample collected in K-EDTA
- Haemolysis by prolonged use of tourniquet, contamination from alcohol
- vigorously shaking the tubes
- respinning in centrifuge
For collecting serums, you use BD SST tubes that contain _ _ and needs to be inverted _ times => _ under _ temperature for _ mins
clot activator 5x specimen clot completely room temp 30 min
Which specimens are heat sensitive - kept chilled
- ACTH
- acetone
- ammonia
- FFA
- lactic acid
- pyruvate
- rennin
Which specimens are photo-sensitive - kept dark
- bilirubin
- B-carotene
- erythrocyte protoporphyrin
What’s the ideal procedure done to a sample after venipuncture?
- centriguge w/in 2hrs & seperate serum
- Serum is stable at:
- Room temp for 8hrs
- Fridge (2-4ºC) for 48hrs
- Freexer (-20ºC) for >48hrs
What are heterophilic Ab? & why may its presence be an issue?
human Ab - arise in response to heterophile Ag from exposure to certain animals or infection
=> lead to false pos results in lab
What must be done with serum samples before tested?
- needs to be clot completely before centrifugation and processing
- red top tubes clot for 45-60 min
- BD SST clot for 30 min
- samples from patients taking HEPARIN (anti-coag) will require MORE TIME to clot
What potenital pre-analytical errors may occur if K+, Na+, Ca+ were below normal?
- Clot formation
- Drip contamination: dilute salts
