MLS Clinical Procedures & Protocols 3

Question 1

Which quality control rule is violated when two consecutive QC values fall more than 2 standard deviations from the mean on the same side?

Accepted Answer

Westgard 2-2s rule

Answer

The 2-2s rule is violated when two consecutive controls exceed ±2 SD in the same direction, signaling a systematic error.

Question 2

A lab receives a request for a STAT troponin on a patient in the ED. The tube arrives unlabeled. What should the MLS do?

Accepted Answer

Reject the specimen and document per policy

Answer

Unlabeled specimens must be rejected per CLSI and accreditation standards because mislabeling errors can cause patient harm; the ED must recollect with proper labeling.

Question 3

What does a corrected reticulocyte count (reticulocyte production index, RPI) below 2 indicate?

Accepted Answer

Hypoproliferative or ineffective erythropoiesis

Answer

An RPI <2 suggests the bone marrow is not producing enough red cells to compensate for anemia, pointing to hypoproliferative or ineffective erythropoiesis.

Question 4

When performing a Gram stain, decolorization with acetone-alcohol is the most critical step. Over-decolorization will cause:

Accepted Answer

Gram-positive organisms to appear pink/red

Answer

Over-decolorization removes the crystal violet-iodine complex from gram-positive organisms, causing them to stain pink with safranin and appear false gram-negative.

Question 5

A 24-hour urine is received for creatinine clearance. The volume is 850 mL. The serum creatinine is 1.2 mg/dL and the urine creatinine is 90 mg/dL. The patient weighs 70 kg and is 175 cm tall (BSA 1.8 m²). What should the MLS check FIRST before calculating clearance?

Accepted Answer

Confirm the collection start and end times are documented

Answer

Accurate timed collection is the most common source of error; without verified start and stop times, the volume cannot be correctly interpreted.

(MLS) Medical Laboratory Scientist Practice Test

(MLS) Medical Laboratory Scientist Practice Test

MLS Clinical Procedures & Protocols 3