Scenario 1:

A phlebotomist collects a Light Blue (Sodium Citrate) tube for PT/INR but the tube is only half full. The specimen is sent to the lab.

What Went Wrong?
The tube was not filled completely.

Why This Is Incorrect
Light blue tubes require a 9:1 blood-to-anticoagulant ratio.
Underfilling alters the ratio and produces inaccurate coagulation results.

Correct Action
Always fill light blue tubes completely. If underfilled, redraw.

Exam Trigger
Light blue + underfilled = reject specimen.

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Scenario 2:

A phlebotomist draws a Lavender (EDTA) tube before a Light Blue (Sodium Citrate) tube.

What Went Wrong?
Incorrect Order of Draw.

Why This Is Incorrect
EDTA contamination can alter coagulation results and falsely decrease calcium levels.

Correct Action
Follow CLSI Order of Draw:
Blood culture → Light Blue → Serum → Green → Lavender → Gray.

Exam Trigger
If coag results are abnormal and EDTA was drawn first → think additive carryover.

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Scenario 3:

After collecting a lavender tube, the phlebotomist vigorously shakes it to mix the blood.

What Went Wrong?
The tube was shaken instead of gently inverted.

Why This Is Incorrect
Shaking causes hemolysis (destruction of red blood cells), leading to inaccurate results.

Correct Action
Gently invert tubes according to required inversion count.

Exam Trigger
Hemolyzed specimen + rough handling = pre-analytical error.

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Scenario 4:

A phlebotomist uses an expired green top tube. Blood flow is slow and the sample clots.

What Went Wrong?
An expired tube was used.

Why This Is Incorrect
Expired tubes may lose vacuum or additive effectiveness, leading to clotting or rejection.

Correct Action
Check expiration dates before collection. Replace expired tubes.

Exam Trigger
Clotted specimen in anticoagulant tube = possible expired tube or improper mixing.

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Scenario 5:

A phlebotomist collects a Gray (Sodium Fluoride) tube before a serum tube.

What Went Wrong?
Incorrect Order of Draw.

Why This Is Incorrect
Gray tube contains additives that may interfere with other chemistry tests if drawn first.

Correct Action
Gray tubes are drawn last to prevent additive contamination.

Exam Trigger
Gray is last in the order.