AACC Laboratory Instrumentation & Technology Flashcards

What is the purpose of a Levy-Jennings chart in laboratory instrumentation monitoring?

Answer: To graphically track QC values and detect systematic or random error trends

Levy-Jennings charts plot sequential QC results against time, with control limits at ±2SD and ±3SD to visualize shifts, trends, and random errors.

In clinical immunoassays, what does the 'hook effect' (prozone phenomenon) cause?

Answer: Falsely low results at very high analyte concentrations due to antigen excess

At very high analyte concentrations, excess antigen saturates both capture and detection antibodies independently, preventing sandwich formation and producing falsely low results.

Which type of analyzer configuration processes one test at a time on a single patient sample?

Answer: Discrete analyzer

Discrete analyzers process individual reaction vessels for each test-patient combination, preventing carryover between tests on different patients.

What is the main advantage of using tandem mass spectrometry (MS/MS) over single-stage MS in clinical newborn screening?

Answer: Ability to simultaneously quantify multiple analytes with high specificity in one run

MS/MS uses two mass analyzers in series, allowing simultaneous identification and quantification of dozens of metabolites from a single dried blood spot with high specificity.

What type of interference is caused by lipemia in photometric assays?

Answer: Optical interference due to light scattering by lipid particles

Suspended lipid particles in lipemic samples scatter light, increasing apparent absorbance and causing falsely elevated results in photometric methods.

In nephelometry used for protein quantification, what is being measured?

Answer: Light scattered at an angle by antigen-antibody aggregates

Nephelometry measures the intensity of light scattered at a specific angle (typically forward or side scatter) by immune complexes formed when antibody binds the target protein.