AACC AACC Instrumentation & Technology

Question 1

Which detection principle is used in most automated clinical chemistry analyzers to measure the concentration of an analyte based on light absorption?

Accepted Answer

Spectrophotometry

Answer

Spectrophotometry measures the amount of light absorbed by a solution at a specific wavelength, which is proportional to the analyte concentration per Beer-Lambert's law.

Question 2

In immunoassay analyzers, what does the term 'hook effect' (or 'high-dose hook effect') refer to?

Accepted Answer

A falsely low result caused by an extremely high concentration of analyte saturating both capture and detection antibodies

Answer

The hook effect occurs when excess antigen saturates the antibodies in a sandwich immunoassay, resulting in a paradoxically low signal and a falsely low analyte result.

Question 3

What is the purpose of a daily linearity check on a clinical chemistry analyzer?

Accepted Answer

To verify that the analyzer can accurately measure analyte concentrations across its full reportable range

Answer

Linearity checks confirm that the analyzer produces proportionally accurate results across the entire clinically reportable measurement range.

Question 4

Which type of electrode is most commonly used in blood gas analyzers to measure pH?

Accepted Answer

Glass pH electrode

Answer

A glass pH electrode measures hydrogen ion activity by detecting the potential difference across a pH-sensitive glass membrane in blood gas analyzers.

Question 5

In mass spectrometry-based clinical assays (LC-MS/MS), what is the role of the internal standard?

Accepted Answer

To correct for variations in sample preparation, ionization efficiency, and instrument response

Answer

An internal standard, typically a stable isotope-labeled analog of the analyte, corrects for matrix effects and procedural variability, improving quantitative accuracy.

AACC - American Association for Clinical Chemistry Certification Practice Test

AACC - American Association for Clinical Chemistry Certification Practice Test

AACC AACC Instrumentation & Technology