TO ERR IS HUMAN ……

We detest it.

We avoid even talking about it.

ERRORSERRORS

Do we really understand them?

Not taught properly during UG and PG

Medical errorsMedical errors

Medical Negligence: Not doing something, which a reasonable person would do or doing something which a reasonable person would not do.

Zero Error Paradigm

Doctors And Health Sector Are Expected To Deliver Every Time

Doctors Themselves & Lay Public Thinks That Doctors Can Achieve This Impossible Ideal Every Time

Objectives

Understand ErrorsFactors that lead to errorsError management

Significance of Error• Potential Leads To:

MisdiagnosisDelays In Treatment Increased Costs

• Avoidable Retests Cost US 200million USD Per Year

• Even A Small Calibration Bias Can Affect Treatment Rates:1% +Ve Bias In Cholesterol Result

5% Increase In Patients Exceeding The Treatment Cut-off3% +ve Bias

15% Increase In Patient Treatment

Comparative Perspective• Error Rates Could Be Reported In Cases Per

Million To Allow Easy Comparison:2.5 Deaths / Million Anaesthesia Cases164 Deaths / Million Car Crashes5000 Cases Of Lost Baggage / Million Air Passengers4566 Laboratory Errors (Results > 6SD) / Million

Results• Kazmierczak & Catrou. Arch Pathol Lab Med 1993;117:714-8

Consequences of the ErrorLoss of lives

Increase in total cost

Loss of trust in System

Diminished satisfaction – Patients/Docs

• Institute of Medicine ReportInstitute of Medicine ReportNov-1999Nov-1999

Understanding Human Behaviour and ErrorDavid Embrey

Human Reliability Associates1, School House, Higher Lane,

Dalton, Wigan,Lancashire. WN8 7RP

Basic Concept

True value - this is an ideal concept which cannot be achieved.

Accepted true value - the value approximating the true value, the difference between the two values is negligible.

Error - the discrepancy between the result of a measurement and the true (or accepted true value).

Sources of Error

Analytical – Random & Systematic

Non-analytical

Random Error

An error which varies in an unpredictable manner, in magnitude and sign, when a large number of measurements of the same quantity are made under effectively identical conditions.

Random errors create a characteristic spread of results for any test method and cannot be accounted for by applying corrections. Random errors are difficult to eliminate but repetition reduces the influences of random errors.

Random Errors

x

x x

x x

True x x x x

Value x x x

x x x

x

x

x

Causes of R.E. (Imprecision) Reagent Variable Reagent Mixing Splashing Calibrators Too Frequent calibrations Variable Age QC material Variable Preparation Variable Age Sample Carry-over Interference

Common to all these materialsEvaporation / Condensation

Instrument Worn out spares Electrical Noise ( E.M.F.) Inconsistent wavelength Inconsistent Temperature Volumetric / Timing Error Contamination of

Tubings/Valves Partial blockages in

Sample/ Rgt probes variable cuvette

thickness Intermittent failure

Systematic Error

An error which, in the course of a number of measurements of the same value of a given quantity, remains constant when measurements are made under the same conditions, or varies according to a definite law when conditions change.

Systematic errors create a characteristic bias in the test results and can be accounted for by applying a correction.

Systematic Errors

x

x x x x x x x

True x

Value

Common Causes of S.E. (Bias)

Manual Error in Reconstitution of Control/ Calibrator/ Reagent / Water quality

Over a Period of Time Changes in Volumetric / Timing Light Source Instrument Spares

Accuracy….

…The agreement between your value and the 'true' value, that is how correct your result is.

Precision….

The reproducibility of your results or the

agreement between replicate

measurements.

The Closer Your Results, Are To Each Other, For The Same Analyte In The Same Serum, The Better

Your Precision.

For Method evaluation, precision should be assessed

in terms of:-

- Within Run Performance (Intra-assay precision)

- Between Run Performance (Inter-assay precision)

Accurate and Precise

Imprecise But Will Be Accurate If You Average The Results

Precise but Inaccurate

Specificity….

…is the ability of a method to measure solely the component of interest.

A lack of specificity will affect A lack of specificity will affect accuracyaccuracy−Falsely elevated or lowered Falsely elevated or lowered

values may be obtainedvalues may be obtained

…is the ability to detect small quantities of a measured component.

Sensitivity…

− will affect both precision and will affect both precision and accuracy at the bottom end of accuracy at the bottom end of the assay range.the assay range.

AIMS OF QC & QA

Quality control simply ensures that results generated by the system are correct.

Quality Assurance is concerned with much more: 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

Quality Assessment - (Proficiency testing) means to determine the quality of the results. & is a challenge to the effectiveness of the QA and QC programs.

Quality Assessment - RANDOX RIQAS, BIORAD EQAS.

Objectives Of Internal QC

To Improve & Maintain Performance (Analytical, Medical & Other Aspects)

To Alert Staff Towards Erroneous Results & To Take Remedial Actions

To Detect Undue Variations In Results & Identify Its Source

LEVY JENNING’S CHART

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Levy Jennings Chart

+3 sd

-3 sd

+2 sd

-2 sd

-1 sd

+1 sd

Analyte

conc.

Target value

Daily Assay Run

Westgard Rules Formulation Based On Statistical Methods

To Analyse Data. To Define Specific Performance Limits To Detect Random And Systematic Errors.

Six Commonly Used Westgard Rules – Two - Warning Four - Mandatory

Violation of Warning rules should Trigger A Review Of Test Procedures, Reagent Performance And Equipment Calibration.

Violation of Mandatory Rules Should Result In Rejection of The Results

Warning Rules

Warning 12SD : When the IQC value exceeds the mean by 2SD. It is an event likely to occur normally in less than 5% of cases. – Random Error

Warning 41SD : If four consecutive IQC values exceed the same limit (mean 1SD) and this may indicate the need to perform instrument maintenance or reagent calibration. – Systematic Error/ Bias

Mandatory Rules Mandatory 13SD : When the IQC value exceeds the mean by

3SD. Regarded as out of control. – Systematic Error Mandatory 22SD : When two consecutive IQC values exceed

the mean on the same side of the mean by 2SD.– Systematic Error

Mandatory R4SD : Applied when the IQC is tested in duplicate or N=2. when the difference in SD between the duplicates exceeds 4SD.

Mandatory 10x : When the last 10 consecutive IQC values are on the same side of the mean or target value. – Systematic Error

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Westgard Rules: 1 3SD

+3 sd

-3 sd

+2 sd

-2 sd

-1 sd

+1 sd

Analyte

Conc.

Target value

Daily Assay Run

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Westgard Rules: 10X

+3 sd

-3 sd

+2 sd

-2 sd

-1 sd

+1 sd

Analyte

Conc.

Target value

Daily Assay Run

Westgard FlowchartControl data

1 point

outside 2 SD

1 point

outside 3 SD

2 consecutive

values outside

the same 2 SD

Difference between

2 controls within

a run

exceeds 4 SD

4 consecutive control

values on one side

of the mean and

further than

1 SD from the mean

10 consecutive

values

on one side of

the mean

In control – report data

Out of control – reject analytical run

Yes

Yes

No

NoNo

NoNo No

YesYes

YesYes

Follow-up Action in the Event of a Violation

Accept the test run in its entirety - only when a warning rule is violated. Initiate a review.

Reject the whole test run - only when a mandatory rule is violated.

Enlarge the grey zone and thus re-test range for that particular assay run - this option can be considered in the event of a violation of either a warning or mandatory rule.

HOW TO INVESTIGATE THE CAUSE…..

……ELIMINATE THE GUESSWORK LAY DOWN A PROTOCOL

Generic Protocol for Remedial Actions

1. Reanalyze the same control immediately.2. Repeat the test using a fresh vial of control. 3. Repeat the test using a new control from a

different lot.4. Check integrity of Reagent system & make

necessary changes. 5. Perform maintenance and rerun the control. 6. Recalibrate (Only if necessary) and rerun the

control. 7. Call an expert for help.

“Knowing is Not Enough;

We Must Apply.

Willing is Not Enough;

We Must Do.”

—Goethe

Planning QC StrategyDefine quality specifications - TEaMeasure – Assess bias & imprecision - TEAnalyse with Normalised OPSpecs

Charts, Power Function graphs, Critical-error graphs, QC selection grids etc.

Implement & ImproveControlMonitor with SIGMA MATRIX

WHAT IS ‘BEYOND QC’ ?

OTHER ISSUES TO BE CONSIDERED

Maintenance & Monitoring of

- Materials, Machine & ManMethod ValidationQC/ Calibrator MaterialS.O.P.sComparison Of Data

Maintenance & MonitoringTemperature maintenance – For Material stability

- Refrigerator, Analysers Water Quality – NCCLS Grade IIElectrical Stability– Earthing, E.M.F.Instruments – P.M., Cuvettes, Bulbs, Tubings.Calibration of equipments - PipettesMaintenance of Procedure ManualsInventory managements & Storage - Materials

MONITORING - Reagents

Reagent characteristics – Vital data pH O.D. of Blanks Factor Range Conductivity for diluents etc.

Calibration factors – Delta checks Reaction Curves – For Ap & As Errors & Action Taken Logs

METHOD VALIDATION

Should be Performed Before Introducing Test

/ New Method / Systems in Routine Practice

by Thoroughly Testing Reference Material or

by Comparison of Test Results Performed by

an Alternative Method

Criteria & Information Sought In Method Validation

Accuracy by running known value samples of M.D.Levels & comparing test results

– For Constant & Proportional errors, Regressional analysis

Precision by running replicates of QC samples with within-the-run, Across-the-run & Between-the-run precision checks & comparison

Linearity Information

QC / CALIBRATOR MATERIAL Third Party Control Materials

Controls with values for your method/ instruments with wider database

Stability & Type of Material (Matrix Effect)

Running Two levels of controls – Provides better error checks across a range

Man

Training of Staff Basic Continuous education

Laying down S.O.P.

COMPARISON OF TEST RESULTS

Peer Group Comparison (Randox 24x7)

Delta Checks (Previous values)

Clinical correlation

THANK YOU !!