Lecturer welcomes students back from the break and explains that this is the final screencast of the lecture series.
Focus: External Quality Assurance (EQA) within the laboratory quality management system.
Internal Quality Control (IQC) only compares the laboratory’s current performance with its own historical data.
Laboratories also need to benchmark their results against:
Other laboratories using the same analyzer, reagent, and analytical principle.
Reference laboratories.
Primary objectives of EQA:
Detect and quantify systematic error (bias).
Monitor and maintain long-term accuracy of analytical methods.
Provide data for lab accreditation and continuous improvement.
ISO 15189 quality policy has two complementary systems:
Internal QC (IQC): Daily monitoring of precision and accuracy.
External Quality Assurance (EQA): Periodic comparison among laboratories.
EQA frequency: Fortnightly or monthly (not daily).
1. Proficiency Testing (PT)
External provider dispatches unknown samples from a common simulated-patient pool.
Participating labs analyze samples, submit results, receive comparative report.
Most Australian pathology laboratories are enrolled in RCPA QAP (Royal College of Pathologists of Australasia Quality Assurance Programs).
2. Rechecking / Retesting
Previously read slides or samples are re-evaluated by a reference lab.
Enables inter-laboratory comparison for difficult-to-standardize assays.
3. Site Visits & Sample Exchange
Applied when PT or retesting is impractical.
Laboratories may exchange specialized samples among themselves for cross-checking.
Regulatory requirement for laboratory accreditation in Australia and globally.
Supplies actionable information:
Highlights abnormal results or trends.
Indicates problems with kits, reagents, instruments, or staff performance.
Guides staff training and process improvement.
Report displays data in multiple visual formats:
Histograms – distribution of participant results.
Yuden (Youden) Plots – comparison of low vs. high concentration specimens.
Levi-Jennings (LJ) Charts – longitudinal performance.
Linearity Plots – response across concentration range.
White zones on plots = allowable performance specification (analogous to \pm 2SD in IQC).
Lab’s own results marked by:
Red triangles (histograms).
Crosses (Yuden plots).
Graph each cycle’s Low-control result (x-axis) vs High-control result (y-axis).
Interpretation:
If the cross sits inside the central square, both results meet acceptance criteria.
Peer Review Box
Inner rectangle within the Yuden plot.
Limits derived from peer-group performance rather than target values.
Allows comparison with labs using identical analytical principle, instrument, and reagent.
Example given: Vitamin D measured by Luminescence Immunoassay (LIA) on DiaSorin Liaison using DiaSorin reagents.
Levi-Jennings Style
Plots results over time against control limits.
Linearity Style
Evaluates analytical linearity across multiple concentration levels.
Result Summary Table
Tabulates numeric result, target, deviation, and performance verdict.
New design introduced in 2020 (example shown for Total Bilirubin).
Core layout retained; visuals refreshed for clarity and aesthetics.
EQA complements IQC to ensure comprehensive quality management of the analytical phase.
Detects systematic errors, biases, reagent/kit issues, instrument drift, and operator problems.
Mandatory for accreditation and integral to continuous improvement cycles.
Lecturer presents flow diagram of total testing process.
Analytical-phase errors include:
Instrument malfunction
Reagent deterioration
Calibration errors
Operator mistakes
Environmental factors
Quality control (IQC + EQA) is the primary defense against these errors.
Additional slides include:
Summary bullets of key QC principles (not detailed in transcript).
Case studies on troubleshooting QC failures (to be discussed live via Collaborate Ultra).
Students encouraged to review cases before live session.
Lecturer signs off with wishes for a great week.