CLS Diagnostic Methods & Technologies 2

Question 1

According to Beer's law, absorbance measured in a spectrophotometer is directly proportional to which variable when path length is held constant?

Accepted Answer

Concentration of the absorbing substance

Answer

Beer's law states A = abc, so absorbance rises linearly with concentration at a fixed path length and molar absorptivity.

Question 2

How does nephelometry differ from turbidimetry when measuring immune complexes?

Accepted Answer

Nephelometry measures light scattered at an angle from the incident beam

Answer

Nephelometry detects light scattered at an angle, while turbidimetry measures the loss of light transmitted in line with the beam.

Question 3

An ion-selective electrode with a valinomycin membrane is used to measure which analyte?

Accepted Answer

Potassium

Answer

Valinomycin is an ionophore that selectively binds potassium ions.

Question 4

A severely lipemic specimen gives a falsely low sodium on an indirect ISE but a normal result on a direct ISE. What explains this?

Accepted Answer

The electrolyte exclusion effect from the increased nonaqueous plasma volume

Answer

Indirect ISEs dilute the total plasma volume, so excess lipid or protein displacing water causes pseudohyponatremia, while direct ISEs measure activity in plasma water.

Question 5

In a competitive fluorescence polarization immunoassay, what happens to the polarization signal as patient analyte concentration increases?

Accepted Answer

Polarization decreases

Answer

More patient analyte displaces labeled tracer from the antibody, and the free tracer rotates rapidly, which lowers polarization.

CLS - Certified Laboratory Professional Practice Test

CLS - Certified Laboratory Professional Practice Test

CLS Diagnostic Methods & Technologies 2