Instrumentation & Technology Applications Flashcards

A consultant is assessing whether a laboratory's automated slide stainer for Gram stains is performing consistently. Which control material is MOST appropriate for daily monitoring?

Answer: Known positive slides containing gram-positive and gram-negative organisms prepared from reference strains

Slides prepared from reference gram-positive and gram-negative organisms verify that the stainer produces correct differential staining and that decolorization is neither under- nor over-performed.

Which regulatory requirement mandates that clinical laboratories using moderate or high complexity tests must document instrument function checks before patient testing each day of use?

Answer: CLIA '88 regulations under 42 CFR Part 493

CLIA '88 (42 CFR Part 493) requires laboratories to perform and document quality control and instrument function checks daily before reporting patient results for moderate and high complexity testing.

A laboratory is validating a new immunoturbidimetric assay for C-reactive protein (CRP). The consultant recommends testing five concentrations in replicates of five to assess:

Answer: Linearity across the analytical measurement range

Testing multiple concentrations spanning the analytical measurement range in replicates allows the laboratory to assess linearity — confirming proportional response across the reported range.

In capillary electrophoresis (CE) used for hemoglobin variant analysis, separation is primarily based on:

Answer: Differences in charge-to-size ratio of hemoglobin variants at a controlled pH

CE separates hemoglobin variants by their differential migration in an electric field, determined by each variant's charge-to-size ratio at the specific buffer pH used.

A laboratory's fluorescence in situ hybridization (FISH) assay for HER2 amplification gives ambiguous results due to poor hybridization signal. The MOST likely technical cause is:

Answer: Inadequate probe denaturation or insufficient target DNA denaturation temperature

FISH signal depends on complete denaturation of both probe and target DNA so they can hybridize; insufficient denaturation temperature or time is the most common cause of weak or absent hybridization signals.

When a laboratory transitions from a manual to an automated cell counter for CSF analysis, the consultant must emphasize validation of which performance characteristic unique to CSF specimens?

Answer: Limit of blank and limit of detection for white and red blood cell counts near zero

Normal CSF has very few cells; the clinical decision thresholds are near zero, making limit of blank and limit of detection critical to ensure the analyzer reliably distinguishes true low-level pleocytosis from background noise.

A laboratory consultant advising on procurement of a new automated coagulation system recommends requesting data on 'lot-to-lot reagent variability.' This is most important because:

Answer: Reagent lot changes can shift assay calibration and require recalibration or validation to maintain result continuity

Lot-to-lot variability in coagulation reagents can cause systematic shifts in results; laboratories must verify that a new lot produces equivalent results or recalibrate to prevent clinically significant errors.