MLS Clinical Procedures & Protocols 5

Question 1

A urine culture grows >100,000 CFU/mL of E. coli. The MLS should perform susceptibility testing using which reference method standard for Enterobacteriaceae?

Accepted Answer

CLSI broth microdilution or disk diffusion with current CLSI breakpoints

Answer

CLSI broth microdilution or disk diffusion using current CLSI M100 breakpoints is the US standard for susceptibility testing of Enterobacteriaceae.

Question 2

Which specimen requires immediate transport on ice to prevent falsely elevated ammonia results?

Accepted Answer

EDTA plasma for ammonia

Answer

Ammonia is produced by amino acid catabolism in RBCs and must be transported on ice and analyzed within 15 minutes to prevent in vitro generation.

Question 3

A new rapid influenza test is being evaluated against viral culture. Sensitivity is 70% and specificity is 99%. What does the low sensitivity mean in practice?

Accepted Answer

30% of true influenza cases will test negative (false negatives)

Answer

Sensitivity of 70% means 30% of patients who truly have influenza will receive a false-negative result and may go undiagnosed and untreated.

Question 4

When performing a manual differential on a peripheral blood smear, the MLS should count cells in which area of the smear?

Accepted Answer

The monolayer area where RBCs just touch or slightly overlap

Answer

The monolayer (counting area) is where RBCs are evenly distributed and just touching, providing accurate morphology and an unbiased differential count.

Question 5

A laboratory is validating a new serum glucose analyzer. Which statistical measure best compares the new method's results against the reference method?

Accepted Answer

Pearson correlation coefficient and linear regression analysis

Answer

Method comparison uses linear regression (slope, intercept) and correlation coefficient to assess bias and proportional error between the new and reference methods.

(MLS) Medical Laboratory Scientist Practice Test

(MLS) Medical Laboratory Scientist Practice Test

MLS Clinical Procedures & Protocols 5