Laboratory - Preservatives Flashcards
How would you preserve a whole blood or plasma sample?
- In an anticoagulant.
How would you preserve a serum sample?
- You don’t need to, just separate once clot has formed.
How would you preserve a urine sample?
- Thymol.
How would you preserve a urine sample for sediment examination?
- Toluene or HCL.
How would you preserve urine for a culture examination?
- Boric acid.
How long can blood samples be stored in the fridge for?
- A few hours
If immediate assessment isn’t possible, what can you do with plasma or serum?
- decant it from centrifuged sample.
How long can plasma and serum be frozen for?
- 1 week.
How long can you store urine in fridge for to test?
- 24 hours.
But what must you do before you test if it has been refrigerated?
- Allow it to return to room temperature.
What does a delay in urine testing cause?
- Bacteria colonisation.
- Production of ammonia.
- Alters pH.
- Can cause crystal formation.
- Alters test results.
What does boric acid do to preserve the urine?
- Keeps pH at 7, prevents bacteria multiplication.
Why shouldn’t you use alcohol to preserve skin for histopathology?
- Causes excessive shrinkage and hardness to sample.
What is good about the neutral buffer solution?
- Reduces artefacts and protects against pH change.
What should you do if using 10% formalin?
- wear PPE as it’s irritant to airways and skin.
