Core Concepts and Principles Flashcards

How many moles per liter are present when 58.5 g of NaCl (MW 58.5) is dissolved to a final volume of 500 mL?

Answer: 2 M

58.5 g is 1 mole, and 1 mole in 0.5 L equals 2 M.

A screening test with very high specificity is most useful for:

Answer: Minimizing false-positive results

High specificity means few healthy individuals test positive, so false positives are rare.

In which phase of testing do the majority of laboratory errors occur?

Answer: Pre-analytical

Most errors arise before analysis, from issues such as misidentification, improper collection, and transport problems.

Which analyte is most falsely increased by in vitro hemolysis?

Answer: Potassium

Red cells contain much more potassium than plasma, so hemolysis releases it and falsely raises the result.

Which fire extinguisher class is appropriate for a fire in an energized electrical analyzer?

Answer: Class C

Class C extinguishers use nonconductive agents designed for electrical fires.

A reference interval is most commonly defined as:

Answer: The central 95% of values from a healthy reference population

Reference intervals usually span the 2.5th to 97.5th percentiles of a healthy population.

What is the main purpose of a delta check?

Answer: To compare a patient's current result with a previous result to detect errors

A large unexplained change from a prior result can reveal misidentification, contamination, or analytical error.