CLS Laboratory Testing & Procedures 2

Question 1

A single control value falls outside the mean ±3 SD. Which Westgard rule is violated, and what action is required?

Accepted Answer

1-3s; reject the run and investigate

Answer

The 1-3s rule detects random error, so the run must be rejected and the problem investigated.

Question 2

Which analyte is most falsely increased by in vitro hemolysis?

Accepted Answer

Potassium

Answer

RBCs contain much more potassium than plasma, so lysed cells release it and falsely raise results.

Question 3

What is the required blood-to-anticoagulant ratio in a light blue top tube used for coagulation testing?

Accepted Answer

9:1

Answer

Sodium citrate coagulation tubes must be filled to a 9:1 blood-to-citrate ratio for accurate results.

Question 4

According to CLSI order of draw, which tube should be collected FIRST?

Accepted Answer

Blood culture bottles

Answer

Sterile blood culture specimens come first to prevent contamination.

Question 5

Why is a gray top tube containing sodium fluoride preferred for glucose testing when processing is delayed?

Accepted Answer

It inhibits glycolysis

Answer

Fluoride inhibits enolase, stopping cells from consuming glucose in the tube.

CLS - Certified Laboratory Professional Practice Test