MLS Diagnostic Procedures & Reporting 3

Question 1

A urine dipstick is positive for blood, but microscopy shows no red blood cells. The most likely explanation is:

Accepted Answer

Myoglobinuria or hemoglobinuria

Answer

The dipstick peroxidase reaction detects heme, so both free hemoglobin (hemoglobinuria) and myoglobin (myoglobinuria) produce a positive result in the absence of intact RBCs.

Question 2

Which coagulation test result pattern is most consistent with disseminated intravascular coagulation (DIC)?

Accepted Answer

Prolonged PT, prolonged aPTT, decreased fibrinogen, elevated D-dimer

Answer

DIC consumes clotting factors and platelets while activating fibrinolysis, resulting in prolonged PT and aPTT, low fibrinogen, and markedly elevated D-dimer.

Question 3

A sputum Gram stain shows >25 squamous epithelial cells per low-power field. The laboratory should:

Accepted Answer

Report the specimen as unsatisfactory and request a new sample

Answer

More than 25 squamous epithelial cells per LPF indicates heavy oral contamination, rendering the specimen unsatisfactory for lower respiratory tract culture; a repeat specimen should be requested.

Question 4

The reference interval for a laboratory test is defined as the central:

Accepted Answer

95% of values from a healthy reference population

Answer

Reference intervals are conventionally set to include the central 95% of values from a healthy reference population, meaning 2.5% fall below and 2.5% above the interval.

Question 5

A patient's serum appears grossly lipemic. Which of the following tests is MOST likely to be falsely elevated due to optical interference?

Accepted Answer

Total protein by biuret method

Answer

Lipemia causes turbidity that scatters light and can falsely elevate spectrophotometric assays such as total protein by the biuret method; direct ISE methods are less affected.

(MLS) Medical Laboratory Scientist Practice Test

(MLS) Medical Laboratory Scientist Practice Test

MLS Diagnostic Procedures & Reporting 3