“ QUALITY CONTROL IN CLINICAL LABORATORY ”

Tapeshwar Yadav(Lecturer)BMLT, DNHE, M.Sc. Medical Biochemistry

OverviewOverview

• Definition of QualityDefinition of Quality• Introduction to Quality ControlIntroduction to Quality Control• Fundamentals of Quality ManagementFundamentals of Quality Management• Total Quality ManagementTotal Quality Management• Quality System And AssessmentQuality System And Assessment• Quality Control & ImplementationsQuality Control & Implementations• External Quality ControlExternal Quality Control• New Quality InitiativesNew Quality Initiatives

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Quality ? sum-total of all the characteristics of a product/service that has a bearing upon the utilization of the product/service to the entire satisfaction of the consumer

Conformance to the requirements of users or customers and the satisfaction of their needs and expectations

1) Acceptable

2) Accessible

3) Affordable

4) Appropriate3

Quality is....

• invisible when GOOD

• impossible to ignore when

BAD

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Introduction

• The issue of laboratory quality has evolved over more than 4 decades since the 1st recommendation for quality control were published in 1965

• Now, quality control is seen as only one part of a total laboratory control program

• Quality also includes: a) Total Quality Management (TQM)→ an activity to

improve pt. care by having the lab monitor, its work to detect deficiencies & subsequently correct them

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b) Continuous Quality Improvement (CQI) or Performance Improvement (PI)→ to improve the pt. care by placing the emphasis on not to make mistakes in the first place

c) Quality Assurance (QA)→ external activities that ensure positive pt. outcomes. It measures what a lab can do to improve reliability

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Fundamentals of Quality Management

Principles of Quality management, assurance, and control have become the foundation by which clinical laboratories are managed and operated

• Total Quality Management of clinical Laboratory• Control of pre-analytical variables• Control of analytical variables• External quality assessment & Proficiency testing

programs

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Total Quality Management

• TQM also referred to as : total quality control (QC), total quality leadership,

continuous quality improvement, quality management science or industrial quality management

• Quality systems in healthcare organization is evolving• Public & Private pressure to contain costs are now

accompanied by pressure for quality improvement (QI)• TQM provides – management philosophy for

organizational development & a management process for improvement of quality in all aspects of work

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• The Universal principles of TQM are(1) Customer focus(2) Management commitment(3) Training(4) Process capability & control(5) Measurement using quality-improvement tools

• Costs must be understood in the context of quality• Quality = conformance to requirements• “Quality costs”

Concepts of TQM

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=“Costs of conformance” + “Costs of non conformance”

Quality Costs

Costs ofConformance

Costs ofNonconformance

Prevention Costs

AppraisalCosts

External failure Costs

Internal failure Costs

Examples:Training

CalibrationMaintenance

Examples:Inspection

Quality control

Examples:Scrap

ReworkRepeat runs

Examples:Complaints

ServiceRepeat request

Understanding of quality & cost leads to a new perspective of relationship b/n these two concepts:

“ Improvement in quality lead to reduction in costs”10

Methodology• Quality improvement occurs when problems are eliminated

permanently• Quality problems are primarily management problems

because only management has the power to change work process

• TQM views the organization as a support structure rather than a command structure

• Most immediate processes required for the delivery of services are those of the frontline employees

• Senior management’s role is to support the frontline employees & empower them

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• QLPs - include analytical processes & the general policies , practices, and procedures that define how all aspects of the work are done

• QC- emphasizes statistical control procedures, but also includes nonstatistical check procedures

• QA- concerned primarily with broader measures & monitors of lab performance (turnaround time, specimen identification, patient identification, test utility)

• QI- a structured problem solving process to help identify the root cause of a problem & a remedy for that problem

• QP- provides the planning steps

Implementing TQM

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These five components, which work together in a feedback loop, illustrate how continuous QI is accomplished and quality assurance is

built into laboratory process

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“Five –Q” framework also defines how quality is managed objectively with the “scientific method”, or the PDCA cycle

QP-provides the planning step, QLP- establishes standard processes, QC & QA provide measures for checks and QI provides a mechanism through which to act on

those measures15

• TQM is also considered as a quality system that is implemented to ensure quality

• QS- “ set of key quality elements that must be in place for an organization’s work operations to function in a manner to meet the organization’s stated quality objectives”

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Quality Systems

The main objective of a laboratory is to provide reliable, timely and accurate test results. This is only possible through consistent monitoring and evaluation of the

laboratory’s performance the implementation and follow-up of corrective

actions for non-conformance to procedure

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Quality Systems

• A reputation based on 10,000 good quality results is damaged by 1 poor quality result

• The establishment of robust testing systems is essential to the success of laboratory services and the treatment program

• The establishment and continuous monitoring of quality systems in each testing laboratory is required for reliable and robust testing

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Quality Systems

• Provide the assurance of the quality of the test results

• Ensure that the lab operations are coordinated, organised and standardised

• Are tools to monitor performance

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• QUALITY ASSESSMENT (EXTR.)

QUALITY: A DEGREE OF EXCELLENCE

• QUALITY CONTROL (INTER.) ++

QUALITY ASSURANCEQUALITY ASSURANCE

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Quality Procedures

• Internal Quality Control (IQC)– includes personnel, instrumentation, document

control, reagent control and corrective action• External Quality Assurance (EQA)

– External quality control is important to ensure the laboratory is performing to an external standard

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Assessment of Quality System

• Audit, On-site inspection

• Internal

• External

• Accréditation

Man-driven Material-driven

• Quality Assessment

• Internal

• External

• Schematic way: External Quality Assessment Scheme (EQAS)

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QC v/s QA

• Quality Control -QC refers to operational techniques that must be included during each assay run to verify that the requirements for Quality are met with

• Quality Assurance - QA refers to all those planned and systematic activities to provide confidence that the results given out by the laboratory are correctThe aim of QC is simply to ensure that the results generated by the test are correct. However quality assurance is concerned with much more: that the right test is carried out on the right specimen and that the right result and right interpretation is delivered to the right person at the right time

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QUALITY ASSURANCE (QA)

• The purpose of QA is the maintenance of the overall quality of patient results

• All factors that effect the test results from the time the test

Pre-analyticPre-analytic AnalyticAnalytic Post-analyticPost-analytic

Specimen collection Specimen collection Specimen transport Specimen transport

Specimen qualitySpecimen quality

Result accuracy Result accuracy Clerical errors Clerical errors

Analytical errors Analytical errors Assay repeat ratesAssay repeat rates

Result reporting Result reporting Record keeping for Record keeping for

patient and QCpatient and QC

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The Quality Assurance Cycle

•Data and Lab Management•Safety•Customer Service

Patient/Client PrepSample Collection

Sample Receipt and Accessioning

Sample Transport

Quality Control

Record Keeping

Reporting

Personnel CompetencyTest EvaluationsTesting

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Quality Control & ImplementationQuality Control & Implementation

Quality control

• Quality control is a vital part of quality assurance– All labs benefit from quality control in terms of confidence in

and reproducibility of test results

• Recording and monitoring test variables such as temperature, reagents, controls and equipment function allows one to look objectively and retrospectively at parameters vital to the accuracy and precision of the test

• Documentation allows one to foresee a potential problem before the situation requires corrective action and adversely effects patient results ￫27

Quality in labs is mutual responsibility of…..

• Laboratory specialists

• Clinicians

• Public health physicians

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Objectives of quality in labObjectives of quality in lab

• Support provision of high quality health-care

– Reduce morbidity

– Reduce mortality

– Reduce economic loss

• Ensure credibility of lab

• Generate confidence in lab results

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Consequences of poor qualityConsequences of poor quality

• Inappropriate action– Over-investigation– Over-treatment– Mistreatment

• Inappropriate inaction– Lack of investigation– No treatment

• Delayed action• Loss of credibility of laboratory• Legal action

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How to implement a QC program?How to implement a QC program?– Establish written policies and procedures

– Assign responsibility for monitoring and reviewing

– Train staff

– Obtain control materials

– Collect data

– Set target values (mean, SD)

– Establish control charts, Eg- Levey-Jennings charts

– Routinely plot control data

– Establish and implement troubleshooting and corrective action protocols

– Establish and maintain system for documentation

Hurdles in Quality Control• Accurate & timely test report are the responsibility of the

laboratory• Total testing process must be managed properly in the

preanalytical, analytical, and postanalytical places

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Control of Preanalytical VariablesPreanalytical variability is defined as errors which occur when non-analytical factors change the conc. of analytes

• Test conducted- appropriate test should be requested & performed

• Patient identification- labeling of specimen may be improper; corrected by bar coding

• Turnaround time (TAT)-should be kept minimum• Laboratory logs- entry of patient & test details in lab

registers & computers• Transcription errors- a substantial risk of transcription

error exists from manual entry of data, even when results are double checked; computerization reduces this error

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• Patient preparation- proper patient preparation is essential to obtain meaningful test result

• Specimen collection- container, anticoagulant, time taken to send specimen to lab, corrected by using vacutainer tubes & collection of samples by lab personnel

• Specimen Transport- critical for some tests• Specimen Separation, aliquoting- monitoring of the

performance of the centrifuge, container used for storage• Personnel- variation fr person to person. Safety

precautions for all specimens. Throughput time to be monitored on a weekly or monthly basis

Control of Preanalytical Variables

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Factors influencing analytical variables

EQUIPMENT RELIABILITY:Meet technical needs, Compatible, User & maintenance friendly, Cost effective, Validated

Procedural reliability using

Standard Operating Procedures

REAGENTS STABILITY, INTEGRITY AND EFFICIENCY:Stable, Efficient, Desired quality, Continuously available, Validated

SPECIFICITY & SENSITIVITY OF SELECTED TEST:Adequate ST, Sufficient SP, cost effective, compatible with, available infrastructure and expertise, interpretable, meets the needs/ objectives, validated

PROFICIENCY OF PERSONNEL: Education, Training, Aptitude, Competence, Commitment, Adequate number, CME, Supervision, Motivation

USE OF APPROPRIATE CONTROLS:• Internal: Labs, Calibrated against national• External: Supplied by manufacturer, National, International

DOCUMENTATION:All the written policies, plans, procedures,

instructions and records, quality control procedures and recorded test results involved in providing a service or the manufacture of a

product

Assessment

ANALYTICAL FACTORS

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• Analytical variables must be controlled carefully to ensure accurate measurements by analytical methods

• Reliable analytical methods are obtained through careful process of :(1) Selection(2) Evaluation(3) Implementation(4) Maintenance(5) Control

• Clear concepts in relation to Analytical methods- Calibration, trueness, accuracy, precision, linearity, & limit of detection

Control of Analytical Variables

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CalibrationCalibration• The calibration function is the relation between instrument

signal(y) and conc. of analyte (x) y=f(x)

or, x=f1(y)• It is set of operations that establish the relationship

between values of quantities indicated by the instrument and the corresponding values realized by ”measurement standards”

• Calibration function may be linear or curved graphically • In automated clinical chemistry instruments , the relation

b/n analyte conc. and signal is often very stable • In traditional chromatography (HPLC), it is customary to

calibrate each analytical run 37

TruenessTrueness

• Trueness of measurements- closeness of agreement b/n the average value obtained from a large series of results of measurements and a true value

• True value- The known, accepted value of a quantifiable property

• Bias- The difference b/n average value & the true value• Measured value- Result of an individual’s measurement of

a quantifiable property

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AccuracyAccuracy

• Accuracy- the closeness of the agreement b/n the result of a measurement & a true conc. of the analyte

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PrecisionPrecision

• Precision- closeness of agreement b/n independent results of measurements obtained under stipulated conditions

• It is the dispersion of replicate measurementsIt is the dispersion of replicate measurements• Inter-assay with multiple runsInter-assay with multiple runs• Intra-assay: within a runIntra-assay: within a run

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PrecisionPrecision• Repeatability (within same run)• Reproducibility or closeness of results to each other

performed under changed conditions of measurement (time,operator,calibrators, reagent lots)– Measured by the standard deviation or coefficient of

variation• Std. dev (σ)/mean(X) x 100 = % C.V.

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ReliabilityReliability

• The ability to maintain both precision and accuracy

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LinearityLinearity• Linearity refers to the relationship between measured &

expected values over the analytical measurement range• May be considered in relation to actual or relative analyte

concentration• Evaluated by plotting measured& expected conc., F-test,

regression analysis of test run• Testing of linearity is related to assessment of trueness

over the analytical measurement range• The presence of linearity is a prerequisite for a high degree

of trueness

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Limit of Detection & QuantificationLimit of Detection & Quantification• Limit of blank (LoB): highest measurement result that is

likely to be observed for a blank sample• Limit of Detection (LoD): lowest concentration of

measurand that can be consistently detected in ≥ 95% of samples tested under routine laboratory conditions and in a given sample matrix

• Limit of Quantification (LoQ): lowest actual amount of analyte that can be reliably detected and at which the total error meets the laboratory’s requirements for accuracyThe distinction b/n different results interpretations is dependent on the relationship b/n LoQ, LoD and LoB

“detected” “detected but below LoQ” “not detected”44

Variables that may cause imprecisionVariables that may cause imprecision

• EquipmentEquipment– Multiple instrumentsMultiple instruments– Pipettes – check precisionPipettes – check precision– Sporadic maintenanceSporadic maintenance

• ReagentsReagents– Different Lots of Reagents lot-to-lot evaluationDifferent Lots of Reagents lot-to-lot evaluation

• StaffStaff– Difference in training, competenciesDifference in training, competencies

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Laboratory EquipmentLaboratory Equipment

• All equipment in the laboratory– Should have instruction manuals regarding proper

use and maintenance requirements– Should be monitored and recorded for quality

control procedures, function checks, preventative maintenance and repairs

• These should be documented and filed in separate log books

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Laboratory EquipmentLaboratory Equipment

• Before putting new equipment or a new method into service – it must be validated- This is accomplishment by correlation and/or agreement

studies- The new method or equipment is validated against old

method and/or equipment• Refrigerators and freezers

- Record serial numbers - Record temperatures daily

Maintaining correct temperatures is vital to maintaining the integrity of reagents and should be maintained as per manufacturers’ instructions.

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Instrument MaintenanceInstrument Maintenance

• CONTROLS and CALIBRATORSCONTROLS and CALIBRATORSManufacturers can provide calibrators and internal controls

• REGULAR MAINTENANCEREGULAR MAINTENANCE– Daily and weekly instrument maintenance – Monthly, six-monthly and annual maintenance as recommended by

supplier

• ROUTINE MAINTENANCEROUTINE MAINTENANCEEnsure that instruments are serviced regularly by a specialised

service engineer and that this maintenance is documented

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Instrument MaintenanceInstrument Maintenance

Required for:

• Producing reliable test results• Minimizing instrument breakdown • Lowering repair costs• Preventing delays in reporting test results• Maintaining productivity• Lengthening instrument life

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PIPETTE’S IMPACT ON QCPIPETTE’S IMPACT ON QC

•Pipette accuracy and precision must checked regularly -

the first time of use and periodically thereafter

•If either fails, it is important to follow the manufacturer’s

instructions for repair and calibration

• Improperly calibrated pipettes will affect our assay and

should be checked for precision and accuracy bi-annually

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PIPETTE’S IMPACT ON QCPIPETTE’S IMPACT ON QC

• Pipettes not passing accuracy checks should be cleaned

and checked for worn parts, and be sent to and

serviced by reliable vendors

• Maintain complete records of pipette calibration function check– Include serial and other identifying numbers of each pipette ￫51

Reagents in LaboratoryReagents in Laboratory

• How to store reagents– Always store according to the manufacturer’s

recommendations– Reagents must be dated and initialed upon receipt– Lot numbers must be recorded in a reagent quality

control record book– After preparation and/or when placed in service,

reagents must be labeled when put “in service” according to the manufacturer’s suggested recommendations ￫52

• Reagent parallel testing– New reagent lots must be checked with old lots using

a normal control before use– The variability for new lots of reagents compared to

the current lot should not be greater than the variability found for triplicate samples of the current lot

– Variability should be within 5%– Results of reagent checks must be recorded, dated

and initialed– Document all lot to lot procedures with date and

variability results

Reagents in LaboratoryReagents in Laboratory

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• Restrict all testing procedures to staff with appropriate technical training– Testing theory– Instruments– Testing procedures

• Perform and document periodic performance assessments on all testing staff

PERSONNEL (Staff)PERSONNEL (Staff)

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PERSONNEL (Staff)PERSONNEL (Staff)

Active participation by everyone working in the system is required to meet quality standards & continuously improve performance

It is laboratory director's responsibility to employ sufficient qualified personnel for the volume and complexity of the work performed

Continuing education program should be provided All documentation should maintained in personnel

file Regular meeting to keep staff informed of changes &

to solicit their suggestion for improving the lab. service

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DocumentationDocumentation

• If you have not documented it,If you have not documented it,

you have NOT done it …you have NOT done it …

• If you have not documented,If you have not documented,

it is a RUMOUR !!!it is a RUMOUR !!!

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Value of DocumentationValue of Documentation

• Ensures processes and outcomes are traceableEnsures processes and outcomes are traceable

• Processes can be audited, thus external Processes can be audited, thus external

assessments can take placeassessments can take place

• Tool for trainingTool for training

• Reminds what to do nextReminds what to do next

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Key DocumentsKey Documents• Results archive

– File results in an organised and easily accessible manner• Laboratory monitoring

– Documentation of temperature monitoring, reagent control, accuracy/precision assays, corrective actions, audit reports

• Instrumentation– SOPs– Equipment files + Manuals– Service history records of the instrument– Records of daily, weekly and monthly calibrations and

maintenance 58

Standard Operating ProceduresStandard Operating Procedures (SOP) (SOP)

• comprehensively written comprehensively written document that describes the document that describes the laboratory procedure and all laboratory procedure and all other related issuesother related issues

• Essential for ensuring Essential for ensuring uniformity in laboratory uniformity in laboratory proceduresprocedures

SOP for TFT

•The SOP should define test performance, tolerance The SOP should define test performance, tolerance limits, reagent preparation, required quality control, limits, reagent preparation, required quality control, result reporting and referencesresult reporting and references

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• The SOPM should be written in CLSI format and must be reviewed and signed annually by the Laboratory director

• Must contain all test methods performed by the laboratory

• The SOPM should be available in the work area. It is the definitive laboratory reference and is used often for questions relating to individual test

• Any obsolete procedures should be dated when removed from SOPM and retained for at least 2 years

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Outline for a Outline for a CLSICLSI Procedure Procedure DocumentDocument

A. Title: intent of the document; conciseB. Purpose or Principle: “the process describes..” info.

regarding theory, clinical implications of examinationC. Procedure instruction: “how to do” a particular steps,

steps involvedD. Related Documents: listing of other procedures usedE. References: reference the source of informationF. Appendixes or attachments: additional informationG. Author(s): author of the document should be

documentedH. Approved Signature: Evidence that the document has

been approved 61

ValidationValidation

is about determining whether is about determining whether something does what it is supposed something does what it is supposed to doto do

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Importance of validationImportance of validation

• Validation - before we introduce somethingValidation - before we introduce something

• Re-validation Re-validation – after we have changed/modifiedafter we have changed/modified

– periodic periodic

• Validation is applied to:Validation is applied to:– SOPSOP– reagentsreagents– equipmentequipment– softwaresoftware

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Factors influencing quality: Factors influencing quality: Post-analyticalPost-analytical

• Right recording and reportingRight recording and reporting

• Right interpretationRight interpretation– Range of normal valuesRange of normal values

• Right turnaround timeRight turnaround time

• Report to right userReport to right user

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Reporting resultsReporting results• Proper procedure includes:

– All data entry results should be verified by a section head or supervisor (when available) and reviewed by management for final interpretation and release of results

– In the event that a report has already been sent out and needs correction, a new report is issued with updated report written on it

• The old report remains in the patient file

– Verbal result reports should be documented, listing the time of the receipt of the report

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HousekeepingHousekeeping

• Surface decontamination of instruments, benchtops, biosafety hoods and general tidiness

• Disposal of biohazardous waste

• Monitoring of fridge, freezer and incubator temperatures

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Statistical Control of Analytical Methods

• Statistics definitions :- Mean, Mode, Median, Standard Deviation- Coefficient of Variation (CV) is the ratio of the SD to the average. It is a measure of relative precision expressed as percentage

• Reference ranges :As per IFCC recommendations, reference values are based on that of a reference individual, it is established in healthy individuals based on application of statistical methods to values generated in the lab

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Reference rangesReference ranges

• What do I do when controls are out of established reference ranges?– Results of the normal donor control are expected to be

within the established reference range. If results exceed reference range limits, follow corrective action:

• Repeat test using same aliquot• If the results still exceed the limits, do not automatically

invalidate patient results– Due to the 95% confidence interval, 1 in 20 specimens from healthy

individuals drawn at random can be outside reference range limits due to biological factors ￫68

Control Materials• Specimens that are analyzed for QC purpose are known as

control materials• Control materials should be available :

-in a stable form-in aliquots or vials-for analysis over an extended period of time, at least 1 yr

• Minimal vial-to-vial variation should exist• Should have preferably the same matrix as the specimen

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Types of Control MaterialsTypes of Control Materials• Assayed

– mean calculated by the manufacturer– must verify in the laboratory

• Unassayed– less expensive– must perform data analysis

• “Homemade” or “In-house” – pooled sera collected in the laboratory– characterized– preserved in small quantities for daily use

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Managing Control MaterialsManaging Control Materials

• Sufficient material from same lot number or serum pool for one year’s testing

• May be frozen, freeze-dried, or chemically preserved according to instructions by the manufacturer

• Requires very accurate reconstitution if this step is necessary

• Always store as recommended by manufacturer

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CalibratorsCalibrators

• Has a known concentration of the substance (analyte) being measured

• Used to adjust instrument, kit, test system in order to standardize the assay

• Sometimes called a standard, although usually not a true standard

• This is not a control

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Control Charts

• A common method to compare the values observed for control materials with their known values is the use of control charts

• Simple graphical displays in which the observed values are plotted versus the time when the observations are made

• Known values are represented by an acceptable range of values

• When plotted points falls within the control limit- method is performing properly

• When points falls outside control limit – problem may be developing 73

LEVY- JENNINGS GRAPHLEVY- JENNINGS GRAPH

L-Js are the process control graphs wherein the daily Q.C. values for all levels of controls are plotted (minimum 20 values) and an inference about the run is drawn , to decide “in control” or “out of control run.”

Advantage: •Simple data analysis and display•Easy adaptation and integration into existing control practices•A low level of false rejection or false alarms•An improved capability for detecting systematic and random errors 74

LEVEY - JENNINGS GRAPHLEVEY - JENNINGS GRAPH

• It should be automatically generated for the parameters chosen in a QC template

• Should be available for viewing by day, month, and other fractions of the year

• Use limit criteria either calculated from the data, or from user defined means and SDs

• Use red for data points that are outliers75

LJ CHART PLOTTED : AN EXAMPLELJ CHART PLOTTED : AN EXAMPLE

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Westgard RulesWestgard Rules

(Generally used where 2 levels of control material are analyzed per run)

• 12S rule

• 13S rule

• 22S rule

• R4S rule

• 41S rule

• 10X rule

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Westgard – 1Westgard – 12S2S Rule Rule

• Warning rule

• One of two control results falls outside ±2SD

• Alerts tech to possible problems

• Not cause for rejecting a run

• Must then evaluate the 13S rule78

112S2S Rule Rule = A warning to trigger careful inspection = A warning to trigger careful inspection of the control dataof the control data

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

12S rule violation

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Westgard – 1Westgard – 13S3S Rule Rule

• If either of the two control results falls outside of ±3SD, rule is violated

• Primarily sensitive to random error

• Run must be rejected

• If 13S not violated, check 22S

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113S3S Rule Rule = Reject the run when a single control = Reject the run when a single control measurement exceeds the +3SD or -3SD control limitmeasurement exceeds the +3SD or -3SD control limit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

13S rule violation

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Westgard – 2Westgard – 22S2S Rule Rule

• 2 consecutive control values for the same level fall outside of ±2SD in the same direction

• Sensitive to systematic error

• Patient results cannot be reported

• Requires corrective action

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222S2S Rule Rule = Reject the run when 2 consecutive control = Reject the run when 2 consecutive control measurements exceed the same measurements exceed the same

+2SD or -2SD control limit+2SD or -2SD control limit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

22S rule violation

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Westgard – RWestgard – R4S4S Rule Rule

• One control exceeds the mean by –2SD, and the other control exceeds the mean by +2SD

• The range between the two results will therefore exceed 4 SD

• Random error has occurred, test run must be rejected

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RR4S4S Rule = Reject the run when 1 control Rule = Reject the run when 1 control measurement exceed the +2SD and the other measurement exceed the +2SD and the other

exceeds the -2SD control limitexceeds the -2SD control limit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

R4S rule violation

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Westgard – 4Westgard – 41S1S Rule Rule

• Requires control data from previous runs

• Four consecutive QC results for one level of control are outside ±1SD

• Sensitive to systematic error

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Westgard – 10Westgard – 10XX Rule Rule

• Requires control data from previous runs

• Ten consecutive QC results for one level of control are on one side of the mean (above or below, with no other requirement on the size of deviation)

• Sensitive to systematic error

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1010xx Rule Rule = Reject the run when 10 consecutive control = Reject the run when 10 consecutive control measurements fall on one side of the meanmeasurements fall on one side of the mean

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

10x rule violation

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External Quality Assessment

• All the control procedures described previously have focused on monitoring of a single lab

• These procedures constitute internal QC, to distinguish them from procedures used to compare the performance of different laboratories are known as external Quality assessment

• These two procedures are complimentary• Internal QC- daily monitoring of precision & accuracy• External QA- long term accuracy of analytical methods

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• EQA results evaluate performance of the laboratory against other laboratories participating in the same program

• Different programs do this in different ways. Eg, t-test is used to test the statistical significance of any difference b/n an individual lab’s observed mean & the group mean

• When the diff. is significant lab. is alerted• Results are instrument and protocol specific• EQA results should be formally documented within the lab

and should be available on request

External Quality Assessment

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• In India EQA is done by Govt. / private organizations- National Accreditation Board for Testing & Calibration Laboratories (NABL) , Dept. of Science & Technology,GOI.(http://www.nabl-india.org)

- ACBI-CMC External Quality Assurance Scheme, Christian Medical College, Dept. of Clinical Biochemistry, Chennai(http://www.cmcvellore.ac.in)

External Quality Assessment in India

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Proficiency testingProficiency testing• Laboratories should all enroll and satisfactorily

participate in a performance evaluation/assessment program

– If conventional proficiency testing is not available, the laboratory must exercise an alternative performance assessment system for determining the reliability of analytic testing (sample splitting for inter-laboratory testing)

– If the lab has more than one method-system for performing tests for an analyte, it must be checked against each other at least twice a year for correlation of patient results ￫92

New Quality Initiatives• Several new quality initiatives have been developed &

implemented to ensure that labs incorporate the principles of Quality Management & QA in daily operation- Six Sigma process- Lean Production- ISO 9000- Joint Committee for Traceability in Laboratory Medicine (JCTLM) Guidelines.

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To ensure that a laboratory practices and provides quality assurance for all phases of testing, the laboratory should:

Enroll and satisfactorily participate in a performance evaluation/assessment program

Establish reference ranges for analytes being testedDocument training and competency assessment for

their technicians Provide review and verification of all results released,

including verbal result reports ￫

SUMMARY

SUMMARY• Quality control is a part of a total laboratory control

program under Total Quality Management• TQM is responsible for organizational development and

management for improved quality in all aspects• Five Qs- Qlp,QC,QA,QI,QP constitute the TQM

framework• Quality Control is achieved through proper documented

and validated interventions at Preanalytical, analytical and post analytical stages

• Quality Assurance is internal Quality assessment plus external Quality assessment

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No matter how good the quality system is on paper, quality cannot be achieved if the theory cannot be translated into practice

Quality costs,

but poor quality costs more …

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References

• Teitz Fundamentals of Clinical Chemistry,6th Ed.• Harold Varley 4th Ed.• Bailey & Scott’s 12th Ed.• Internet

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Thank You 98