Sampling

Question 1

Discuss Lithium Heparin blood tubes

Answer 1

Purpose of Additive: Prevents clotting and coagulation of blood.
Sample type: Blood (plasma)
Use: This is the most commonly used blood bottle within Clinical Biochemistry example of tests include: (usually have green tops)
Electrolyte Profile
Bone Profile
Liver Function Tests
Amylase
CRP
Troponin

Question 2

Discuss clot activator blood tubes

Answer 2

Additive: Clot activator (usually have yellow tops)
Purpose of Additive: Promotes clotting of blood. The sample must be given time for the clot activator to take effect before centrifugation.
Sample type: Blood (serum)
Use: Lithium Heparin samples are not suitable for all tests. In these instances this tube is used within Biochemistry. Examples of use include:
Lithium
Serum Protein Electrophoresis.

Question 3

What is separator gel?

Answer 3

samples with clot activator or Lithium Heparin, contain a gel separator.
During centrifugation the red cells are separated from the serum/plasma by centrifugal force. The red cells (heaviest) fall to the bottom and the serum plasma stays at the top.
This gel forms a barrier between the 2 layers.
Prevents mixing of the red cells and serum /plasma
Increases STABILITY of the sample. For example, in vitro potassium leaks from the red cells, this would increase the measured potassium in the serum, but this would not be reflective of the normal serum / plasma levels.

Question 4

Discuss the K3 EDTA blood tubes

Answer 4

Additive: K3 EDTA
Purpose of Additive: Chelates calcium, preserving red cell morphology
Sample type: Whole Blood
Use: This is the most commonly used blood bottle within Clinical Haematology, example of tests include:
Full Blood Count
ESR
Also used within Clinical Biochemistry:
HbA1c

Question 5

Discuss sodium citrate blood tubes

Answer 5

Additive: Sodium Citrate
Purpose of Additive: Binds calcium to prevent clotting (anticoagulant)
Sample type: Whole Blood
Use: Used within Clinical Haematology, example of tests include:
D-Dimer
Pro-Thrombin Time

Question 6

Discuss fluoride oxalate blood tubes

Answer 6

Additive: Fluoride oxalate
Purpose of Additive: Inhibits glycolysis
Sample type: Mostly blood (plasma), but also CSF and fluids.
Use: Used for measurement of glucose

Question 7

Discuss boric acid sample containers

Answer 7

Additive: Boric Acid
Purpose of Additive: Bacteriostatic. Stops bacteria from reproducing without killing them.
Sample type: Urine
Use: Urine Culture

Question 8

Discuss a sample container with no additive - a sterile container

Answer 8

Additive: None. Sterile container.
Purpose of Additive: A sterile environment to transport samples.
Sample type: Various fluids - Sputum / drain fluid
Use: Example – respiratory culture

Question 9

Discuss charcoal sample containers

Answer 9

Additive: Charcoal
Purpose of Additive: Mops up antibiotics
Sample type: Swab
Use: Example - Gonorrhoeae

Question 10

Discuss Amies gel sample containers

Answer 10

Additive: Amies Gel
Purpose of Additive: Prevents sample drying out. Maintains anaerobic environment
Sample type: Swab
Use: Example – Group B Strep

Question 11

Discuss growth mixture sample containers

Answer 11

Additive: Growth mixture
Purpose of Additive: To allow bacteria growth.
Sample type: Blood
Use: Blood culture
This bottle also has a pH detector at the bottom. Production of C02 causes pH change.

Question 12

What is formalin used for?

Answer 12

When tissue is removed from the body there is no longer a blood supply, and the tissues starts to die.
Tissues needs to be preserved.
Fixation prevents autolysis (destruction of cells and tissues by own enzymes) and putrefaction (destruction of cells or tissues by micro-organisms).
Samples are routinely fixed in Formalin which hardens the tissue.
Once samples are taken, they can be transported to the laboratory in containers pre-filled with Formalin.
The correct size of container for the specimen should be selected.

Question 13

How do Staff Know what Sample to send for a test?

Answer 13

Laboratory User Handbook

Question 14

What is a request form?

Answer 14

Prompts the requestor to provide all the information required.
Provides a ‘menu’ of tests to select from.
Helps to guide the requestor to use the correct sample for the test requested.

Question 15

What 3 ways are samples transported?

Answer 15

-Pneumatic Tube System (PTS)
Connects the wards to the laboratory.
Quick transit of samples.
Should only be used for urgent samples
-Hospital Porters
Collects samples from the wards at regular intervals (every few hours)
Inpatient requests
Can also collect specific samples that can’t go in PTS (such as CSF)
-Van collections
Collects samples from GP’s and satellite hospitals.
Collections several times a day.
Most of the work arrives in this way.

Question 16

What samples must be packaged separately with a hazard warning label and are not suitable for PTS? (pneumatic tube system)

Answer 16

Hazard Group 3 samples (TB, Hep B, HIV etc.)

Question 17

How are samples sorted/prioritised into urgent, inpatient, routine?

Answer 17

based on Test requested – such as Troponin (heart attack)
Source- such as Emergency Department
Clinical need – any test from any location but is clinically required urgently.
Red flags (Histopathology / Cytopathology)

Question 18

What preparation may samples require for analysis?

Answer 18

Centrifugation (Biochemistry)
Slides prepared (Histo / Cyto)
Incubation / plating (Micro)

Question 19

What are sample checked to ensure?

Answer 19

The sample type is correct for the test that is requested.
The details are sufficient on form and sample.
The details match on form and sample (Minimum Acceptance Criteria).
Identify any errors i.e. sample is too old
Form and sample given a unique accession number!!

Question 20

What are some unrepeatable samples?

Answer 20

CSF samples
Timed samples
Histopathology samples

Question 21

How are samples storage monitored?

Answer 21

Samples must be stored under the correct conditions – room temperature, refrigerated, frozen.
Samples must be safe and secure.
Temperature probes are used.
This is monitored a system which will flag temperature excursions.

Question 22

What mistakes can be seen when a requestor submits a sample for testing?

Answer 22

Incorrect container
Fails to meet the Minimum Acceptance Criteria
Sample too old

Question 23

Where are test requests put?

Answer 23

Test requests are put on to the Laboratory Information Management System (LIMS).
At this point the unique accession number is linked to the patient information and the test request.