Specimen Processing - Centrifugation

Question 1

Describe the composition of the three layers in a centrifuged anticoagulated specimen.

Answer 1

1. The layers are:

• large red cell layer at the bottom (about ½ vol.)
• thin whitish WBC and platelet layer in the middle
• large straw colored upper layer (about ½ vol.) which is the plasma layer

Question 2

2. State the minimum clotting times for the following:
   a) tube with thrombin activator
   b) tube with glass or silica activator
   c) plain red topped tube

Answer 2

a) 5 min b) 30 min c) 60 min

Question 3

Give the reason why the following procedures are not recommended:

a) Centrifuging an unstoppered specimen.

Answer 3

This will likely create aerosols, the specimen may concentrate due to evaporation.

Question 4

Give the reason why the following procedures are not recommended:

Centrifuging a specimen before it has fully clotted

Answer 4

The fibrin will continue to form and the fibrin clot may plug lines in instruments or plug pipets.

Question 5

Give the reason why the following procedures are not recommended:

Operating a centrifuge which is NOT balanced .

Answer 5

The centrifuge will vibrate, the specimen will not separate properly and the specimen tube may break.

Question 6

Give the reason why the following procedures are not recommended:

Braking a centrifuge.

Answer 6

The separation of the specimen will be not as distinct.

Question 7

Give the reason why the following procedures are not recommended:

Opening the lid of a centrifuge prior to it coming to rest.

Answer 7

This is extremely dangerous; if a tube breaks, the broken glass will fly out of the centrifuge and may injure someone.

Question 8

How long and in what position may serum on a SST specimen be stored?

Answer 8

The gel barrier will remain intact for 48 hours if the specimen is stored upright.

Question 9

List the 4 types of anticoagulants.

Answer 9

Heparin, EDTA, Citrates, and Sodium Fluoride