Laboratory Quality & Statistics – Vocabulary Flashcards

A set of vocabulary flashcards covering key terms and definitions related to laboratory quality management, QC statistics, and foundational statistical concepts for MLAB I – Laboratory Skills I.

Quality Assurance (QA)

A comprehensive program that monitors the total testing process to guarantee quality patient care by tracking outcomes and reviewing appropriateness, applicability, and timeliness.

Quality Control (QC)

A component of QA that verifies the reliability of analytical test results through standards, controls, and statistical analysis.

Internal QC (Statistical QC)

Daily evaluation of assay precision using control materials run with patient samples.

External QC (Proficiency Testing)

Assessment of assay accuracy by comparing a laboratory’s results on unknown samples with those of peer laboratories or reference values.

Proficiency Testing (PT)

A regulated process in which samples of known concentration (unknown to the lab) are analyzed to evaluate a laboratory’s performance, accuracy, and reporting practices.

Delta Check

An internal QC procedure comparing current patient results with previous results to detect significant discrepancies before reporting.

Standard Operating Procedure (SOP)

A written, validated procedure detailing purpose, specimen requirements, step-by-step method, limitations, corrective actions, references, and approval signatures.

Calibration

The process of checking, standardizing, or adjusting an instrument or method so it provides accurate results within an acceptable range.

Standard (Reference Material)

A highly purified substance of exact concentration used to calibrate instruments and establish accurate measurement.

Control Specimen

A material with a known analyte concentration run with patient samples to monitor the performance of procedures and instruments.

Commercial Control

A lyophilized or liquid control product that resembles a patient sample and contains a stated analyte concentration for routine QC testing.

Blind Duplicate Patient Sample

A previously tested patient specimen re-submitted as an unknown to evaluate laboratory precision and accuracy.

Accuracy

The closeness of a measured result to the true or target value.

Precision (Reproducibility)

The closeness of agreement between repeated measurements on the same sample; measure of repeatability.

Systematic Error

A consistent bias affecting all results in the same direction; impacts accuracy and shifts the mean.

Random Error

Unpredictable variation affecting individual results; impacts precision and increases standard deviation.

Shift (QC)

Five or more consecutive control results on the same side of the mean at a constant level, indicating a sudden systematic error.

Trend (QC)

Five or more consecutive control results that progressively increase or decrease, suggesting gradual systematic change (e.g., reagent deterioration).

Gaussian Curve

The normal bell-shaped distribution of values around a mean when plotted graphically.

Mean (x̄)

The arithmetic average of a set of values obtained by dividing the sum by the number of values.

Median

The middle value of an ordered data set, with half the values above and half below.

Mode

The value that occurs most frequently in a data set.

Variance (s²)

A statistical measure indicating how far data points are spread around the mean; the square of the standard deviation.

Standard Deviation (SD)

The square root of the variance; quantifies the spread of data points around the mean and is used to set QC limits.

Coefficient of Variation (%CV)

Relative measure of precision calculated as (SD ÷ mean) × 100; allows comparison of variability between methods.

Confidence Limit (±2 SD)

Range around the mean that encompasses ~95% of normally distributed values; common QC acceptability boundary.

Levey-Jennings Chart

A graphical QC tool plotting control results against time with mean and SD limits to detect errors, shifts, and trends.

Westgard Rules

A set of decision criteria applied to Levey-Jennings charts to determine when a measurement system is in or out of control.

Sensitivity

The proportion of true positive cases correctly identified by a test.

Specificity

The proportion of true negative cases correctly identified by a test.

Predictive Value (PV)

The ability of a test result to predict the presence (positive PV) or absence (negative PV) of disease in the tested population.

Reference Range (Reference Interval)

The established upper and lower limits of analyte values expected for a healthy population, reported with patient results.

Critical Value (Panic Value)

A test result significantly outside the reference range that indicates a life-threatening condition requiring immediate reporting.

Preanalytical Phase

All processes before sample analysis (patient prep, collection, labeling, transport, storage) that can influence test results.

Postanalytical Phase

Processes after analysis (result verification, transcription, reporting, interpretation) that affect the delivery and use of test results.

Coefficient of Variation (%CV)

The ratio of SD to mean expressed as a percentage; used for comparing precision among different methods or analytes.