Clinical Laboratory Quality Assurance

Clinical laboratory quality assurance (QA) encompasses the systematic activities implemented to ensure that laboratory testing produces accurate, reliable, and clinically relevant results. A comprehensive QA program addresses all phases of the testing process—pre-analytical, analytical, and post-analytical—to minimize errors and optimize patient care outcomes.

The Total Testing Process

Laboratory quality assurance must address the complete testing cycle, as errors can occur at any phase. Studies consistently show that pre-analytical and post-analytical errors account for the majority of laboratory errors.

Phase	Activities	Error Rate
Pre-analytical	Test ordering, specimen collection, transport, processing	46-68% of errors
Analytical	Sample analysis, instrument function, reagent quality	7-13% of errors
Post-analytical	Result review, reporting, interpretation, action	19-47% of errors

Pre-Analytical Quality Assurance

The pre-analytical phase includes all steps from test ordering through specimen preparation for analysis. Standardizing these processes reduces the most common source of laboratory errors.

Test Ordering

• Appropriate Test Utilization: Clinical decision support to guide test selection
• Order Entry Accuracy: Patient identification verification, correct test selection
• Clinical Information: Relevant diagnosis codes, medications, timing considerations
• Duplicate Order Prevention: Alerts for redundant testing

Specimen Collection

Proper specimen collection is critical for accurate results. Key quality elements include:

• Patient Identification: Two-identifier verification per Joint Commission requirements
• Correct Container Selection: Appropriate tube type, additive, volume requirements
• Order of Draw: Proper sequence to prevent additive carryover
• Collection Technique: Minimize hemolysis, contamination, and dilution
• Specimen Labeling: At bedside, with required elements (name, DOB, date/time, collector)
• Special Handling: Temperature requirements, light protection, timing considerations

Specimen Transport and Processing

• Transport Conditions: Temperature maintenance, protection from light, biohazard containment
• Timeliness: Maximum acceptable time from collection to analysis (varies by analyte)
• Specimen Receiving: Verification of specimen acceptability, documentation of issues
• Processing Procedures: Centrifugation parameters, aliquoting, storage conditions
• Chain of Custody: Documentation for forensic and drug testing specimens

Specimen Rejection Criteria

Rejection Reason	Examples	Prevention Strategy
Identification Errors	Unlabeled, mislabeled, illegible	Bedside labeling, barcode verification
Wrong Container	Incorrect tube type for test	Collection guides, visual aids
Quantity Not Sufficient	Underfilled tubes, clotted specimens	Training, minimum volume indicators
Hemolysis	Traumatic collection, improper handling	Technique training, needle gauge
Contamination	IV fluid dilution, cross-contamination	Collection site selection, aseptic technique
Delay	Exceeded stability time	Pneumatic tubes, frequent transport

Analytical Quality Assurance

The analytical phase focuses on ensuring that instruments and methods produce accurate and precise results. Proper calibration, quality control, and method validation are essential components.

Instrument Calibration

• Calibration Frequency: Per manufacturer instructions, regulatory requirements, and when indicated by QC failures
• Calibration Verification: Validate calibration across reportable range using certified materials
• Traceability: Calibrators traceable to reference methods or certified reference materials
• Documentation: Records of all calibration activities and results

Quality Control Programs

Quality control (QC) materials are analyzed alongside patient samples to monitor analytical performance:

• Control Selection: Matrix-appropriate materials at clinically relevant concentrations
• Control Frequency: Minimum per regulatory requirements, additional based on risk assessment
• Multi-level Controls: Normal and abnormal levels to verify linearity
• Third-Party Controls: Independent verification of manufacturer controls
• Westgard Rules: Statistical rules for QC interpretation and troubleshooting

Common Westgard Rules

Rule	Description	Error Type
1:2s	One control exceeds mean ±2SD	Warning rule
1:3s	One control exceeds mean ±3SD	Random error
2:2s	Two consecutive controls exceed same mean ±2SD	Systematic error
R:4s	Range between controls exceeds 4SD	Random error
4:1s	Four consecutive controls exceed same mean ±1SD	Systematic error
10x	Ten consecutive controls on same side of mean	Systematic error

Proficiency Testing

External proficiency testing (PT) provides an objective assessment of laboratory performance by comparing results with peer laboratories. CLIA laboratory accreditation requirements mandate participation in approved PT programs.

• Enrollment: Required for all regulated analytes
• Handling: PT samples must be tested like patient samples
• Review: Results analyzed for acceptable performance
• Corrective Action: Investigation and remediation of failures
• Documentation: Records maintained for inspection

Post-Analytical Quality Assurance

The post-analytical phase includes result verification, reporting, and ensuring appropriate clinical action based on results.

Result Verification

• Delta Checks: Comparison with previous patient results to identify collection or identification errors
• Critical Value Review: Verification and immediate reporting of life-threatening results
• Consistency Checks: Related test results evaluated for physiological plausibility
• Reflex Testing: Automatic follow-up testing based on initial results
• Technical Review: Instrument flags, QC status, and pending results verified

Critical Value Reporting

Critical (panic) values require immediate communication to responsible caregivers. Programs must address:

• Defined Thresholds: Facility-specific critical value list based on clinical significance
• Timely Notification: Maximum acceptable time from result to provider notification
• Read-Back Verification: Receiver confirms understanding of reported value
• Documentation: Date, time, person notified, read-back confirmation
• Escalation Procedures: Process when primary caregiver cannot be reached

Amended Reports

When results require correction or amendment:

• Document reason for amendment
• Maintain original result in record
• Clearly identify amended result
• Notify affected caregivers of significant changes
• Track amendment frequency as quality indicator

Method Validation and Verification

Before implementing new tests or instruments, laboratories must demonstrate acceptable performance through validation (laboratory-developed tests) or verification (FDA-cleared tests).

Verification Elements (FDA-Cleared Methods)

Element	Description	Acceptance Criteria
Precision	Repeatability and reproducibility	Within manufacturer claims
Accuracy	Comparison with reference or validated method	Acceptable correlation/bias
Reportable Range	Verify linearity across claimed range	Within manufacturer claims
Reference Range	Verify applicability to patient population	Clinically appropriate

Additional Validation Elements (LDTs)

• Analytical Sensitivity: Limit of detection and quantitation
• Analytical Specificity: Interference and cross-reactivity studies
• Clinical Validation: Sensitivity, specificity, predictive values
• Stability Studies: Specimen and reagent stability
• Reference Range Establishment: Population-specific normal values

Personnel Competency

Qualified personnel are essential for laboratory quality. Competency assessment must be ongoing and documented.

Competency Assessment Elements

• Direct Observation: Watching performance of routine tasks
• Specimen Assessment: Evaluation of specimen acceptability decisions
• Written Examinations: Testing of theoretical knowledge
• Blind Samples: Testing unknown specimens
• Problem Solving: Troubleshooting and QC failure resolution
• Checklist Assessment: Verification of procedural compliance

Assessment Frequency

• Initial training verification before independent work
• Within 6 months of initial assessment
• Annually thereafter
• When new procedures or instruments implemented
• When performance issues identified

Quality Improvement and Indicators

Continuous quality improvement requires systematic monitoring of key performance indicators and implementation of corrective actions when issues are identified.

Common Laboratory Quality Indicators

Indicator	Calculation	Target
Specimen Rejection Rate	Rejected specimens / Total specimens	<2%
Turnaround Time	Collection to result time	Varies by test
Critical Value Notification	Time from result to notification	<30 minutes
Amended Report Rate	Amended reports / Total reports	<0.5%
PT Success Rate	Acceptable results / Total PT challenges	>90%
QC Failure Rate	Out-of-control events / Total QC runs	<5%

Related Resources

For additional information on laboratory quality and related topics, explore these resources:

• Knowledge Base Hub – Comprehensive healthcare equipment guides
• Point-of-Care Testing (POCT) Guide
• CLIA Laboratory Accreditation Requirements
• Documentation Hub – Technical equipment specifications
• Compliance Standards Hub – Regulatory requirements and guidelines