MLS Clinical Testing & Analysis 3

Question 1

A type and screen is ordered pre-operatively. The antibody screen is positive. What is the next step?

Accepted Answer

Perform antibody identification panel

Answer

A positive antibody screen requires an antibody identification panel to determine the specificity of the unexpected antibody before blood is issued.

Question 2

In cerebrospinal fluid analysis, xanthochromia is most commonly caused by:

Accepted Answer

Oxyhemoglobin and bilirubin from red cell breakdown

Answer

Xanthochromia results from oxyhemoglobin and later bilirubin released as RBCs lyse after subarachnoid hemorrhage, distinguishing it from a traumatic tap.

Question 3

Which mycobacterium is the most common cause of pulmonary tuberculosis in immunocompetent US adults?

Accepted Answer

Mycobacterium tuberculosis

Answer

Mycobacterium tuberculosis is the etiologic agent of classic tuberculosis and remains the leading mycobacterial pathogen in immunocompetent individuals.

Question 4

A serum potassium is critically elevated. The specimen is hemolyzed. What should the laboratory do?

Accepted Answer

Reject the specimen and request a recollect

Answer

Hemolysis releases intracellular potassium, falsely elevating serum K⁺; the specimen must be rejected and a fresh non-hemolyzed sample collected for accurate results.

Question 5

Which coagulation test is used to monitor unfractionated heparin therapy?

Accepted Answer

Activated partial thromboplastin time (aPTT)

Answer

Unfractionated heparin potentiates antithrombin to inhibit intrinsic pathway factors, which is measured by the aPTT; therapeutic range is typically 1.5–2.5× control.

(MLS) Medical Laboratory Scientist Practice Test

(MLS) Medical Laboratory Scientist Practice Test

MLS Clinical Testing & Analysis 3