CPHT Order of Draw & Tube Additives 3

Question 1

How many times should a lavender (EDTA) tube be gently inverted immediately after blood collection?

Accepted Answer

8-10 inversions

Answer

3-4 inversions

Answer

5-6 inversions

Answer

12-15 inversions

Question 2

A sodium citrate tube must be filled to what level for coagulation results to be considered valid?

Accepted Answer

Within ±10% of the required fill volume

Answer

At least 50% full

Answer

At least 75% full

Answer

Exactly 100% full — any underfill is rejected

Question 3

If EDTA carryover from a lavender tube occurs into a serum chemistry tube, which electrolyte result is most likely to be falsely elevated?

Accepted Answer

Potassium (K+)

Answer

Sodium (Na+)

Answer

Chloride (Cl-)

Answer

Bicarbonate (HCO3-)

Question 4

A phlebotomist accidentally draws an SST (gold) tube before the light blue (citrate) tube. What is the correct corrective action?

Accepted Answer

Draw a discard tube to flush residual clot activator before collecting the citrate tube

Answer

Proceed normally; draw the citrate tube next without any modifications

Answer

Remove the needle, apply new needle, and restart the entire collection

Answer

Label the citrate tube noting the order deviation and send it to the lab as is

Question 5

For which analyte is a plain red top tube (no gel separator) preferred over a gold SST tube?

Accepted Answer

Serum iron testing

Answer

Basic metabolic panel (BMP)

Answer

Thyroid-stimulating hormone (TSH)

Answer

Hepatitis B surface antigen

Question 6

How many inversions are recommended for a gold SST tube immediately after blood collection?

Accepted Answer

5-6 inversions

Answer

3-4 inversions

Answer

8-10 inversions

Answer

No inversions — place upright and allow to clot undisturbed

Question 7

How does sodium fluoride in a gray top tube preserve glucose levels in a blood specimen?

Accepted Answer

It inhibits the glycolytic enzyme enolase, stopping glucose consumption by red blood cells

Answer

It chelates calcium to halt all cellular metabolism

Answer

It lyses red blood cells to immediately release all intracellular glucose

Answer

It maintains an acidic pH that denatures all metabolic enzymes