Quality Control & Quality Assessment – Lecture Review

Twenty Q&A flashcards covering definitions, procedures, error types, charts, Westgard rules, statistical measures, equipment maintenance, and benefits related to Quality Control and Quality Assurance in the laboratory.

What is the definition of Quality Assurance (QA) in the laboratory?

The coordinated process of providing the best possible service to patients and physicians by monitoring and controlling personnel competence, materials, methods, reagents, instruments, and the reliable reporting of test results.

How is Quality Control (QC) defined in a clinical laboratory?

A set of laboratory procedures designed to ensure that test results are accurate and reliable as diagnostic tools, typically through testing known samples, charting results, and performing statistical analyses.

Which key characteristic distinguishes QA from QC?

QA is proactive and broad, aiming to prevent quality failures during the entire process, whereas QC is reactive and narrow, detecting errors after a product or test is performed.

List three essential steps when implementing a QC program.

1) Establish written policies and assign monitoring responsibility; 2) Obtain control materials, collect data, set target values (mean, SD), and plot Levey-Jennings charts; 3) Create troubleshooting/corrective-action protocols and maintain documentation.

What is the primary difference between Internal QC and External QC?

Internal QC is performed daily using control samples of known concentration, while External QC is performed periodically (e.g., weekly or monthly) using controls of unknown concentration for independent performance comparison.

State two goals of a Quality Assessment (QA) program.

1) Detect, evaluate, correct, and prevent problems in test systems; 2) Continuously improve processes even when no problems are identified.

Name four variables that can affect the quality of laboratory results.

Personnel education/training, specimen condition, reagent quality, equipment status, control materials, result interpretation, transcription, and reporting.

Define a systematic error and give one common cause.

An error that remains constant or changes in a predictable manner under the same conditions, creating bias in results; causes include incorrect calibration or consistent temperature variation.

Define a random error and provide one example.

An unpredictable error that varies in magnitude and sign among repeated measurements under identical conditions; examples include pipetting inconsistencies or incubation time fluctuations.

What is the purpose of a Levey-Jennings chart?

To graph QC data, displaying mean and standard deviation limits, and visually distinguishing between normal variation and systematic error in laboratory assays.

Which Westgard rule signals a single point beyond ±3 SD?

The 13s rule.

Which Westgard rule triggers when two consecutive control points exceed ±2 SD on the same side of the mean?

The 22s rule.

Describe the Westgard R4s rule.

A quality control alert occurring when one control point exceeds +2 SD and the next exceeds –2 SD (or vice versa), indicating a 4 SD difference between two consecutive points.

What condition does the Westgard 41s or 10x rule detect?

41s: four consecutive points beyond ±1 SD on the same side; 10x: ten (or eight/twelve) consecutive points on one side of the mean, indicating a systematic shift.

Why are mean and standard deviation critical in QC charts?

They establish the center line and control limits (±1, ±2, ±3 SD), enabling detection of out-of-control situations through comparison of control results against expected variability.

Define the Coefficient of Variation (CV) and its primary use.

CV = (Standard Deviation ÷ Mean) × 100%; a unit-less measure used to compare relative variability between different data sets or analytical methods.

Differentiate between accuracy and precision in laboratory testing.

Accuracy reflects closeness of results to the true/reference value (bias), while precision reflects closeness of repeated results to each other (repeatability/reproducibility).

State two reasons why regular equipment maintenance and calibration are vital.

They sustain instrument performance, ensure data accuracy/reproducibility, reduce breakdowns and repair costs, and lengthen instrument life.

List three documented best practices for laboratory equipment care.

Clean before and after use, schedule professional calibration, promptly repair/replace faulty parts, and document all maintenance events.

Give three benefits of routine instrument calibration.

Provides traceability to national/international standards, increases confidence in results, reduces failure/rejection rates, improves product/service quality, and enhances safety.