Biochemical tests 2

Question 1

What are laboratory errors?

Answer 1

any 
defects from ordering tests to 
reporting results and 
appropriately interpreting and 
reacting on these

Question 2

Where do majority of the errors come from?

Answer 2

Pre-analytical phase

Question 3

What does the pre-analytical phase include?

Answer 3

All the steps that a test sample must undergo before the actual test is carried out i.e
 Sample collection
 Sample labeling (Misidentification)
 Sample handling
 Transportation
 Storage
 Sample preparation

Question 4

What should be avoided in blood sample collection?

Answer 4

Avoid drawing blood above the IV line and from edematous tissue.

Avoid prolonged stasis due to tourniquet as this can lead to hemoconcentration and possibly hematoma. It can also cause a sieving effect where water and ions are forced out of blood vessels and larger molecules are concentrated. This falsely raises concentrations of hormones and protein in the blood stream and decrease electrolytes.

Question 5

What are problems that can occur in blood sample transportation?

Answer 5

• Sending in a blood sample too early after the
administration of a drug can lead to misleadingly high
values in therapeutic monitoring
• Interpretation of some tests (Eg. Cortisol, blood glucose) is critically dependent on the time of day when the blood
was sampled and delivered
• Sample not kept on ice  Sample for arterial blood gas
analysis

Question 6

What are reasons for specimen rejection?

Answer 6

• Absence or misidentification of specimen
• Inadequacy of specimen for analysis
• Specimen integrity and suitability  hemolysis, clot,
contamination
• Container suitability
• Prolonged storage

Question 7

What is hemolysis and how can it occur

Answer 7

Hemolysis is the Rupture of red blood
cells leading to significant increase in
potassium

• Can occur from two sources
In-vivo hemolysis comes from Pathological 
conditions, such as autoimmune 
hemolytic anemia or transfusion 
reaction

In-vitro hemolysis comes from Improper
specimen collection, specimen
processing, or specimen transport