Quality Control

IT IS A BASIC SAFETY PRACTICE TO MONITOR ANALYTICAL QUALITY OF MEASUREMENT.

To detect changes from stable day to day operation and eliminate reporting of results with medically important errors.`

OBJECTIVES

1.To determine how to establish the analytical goal and quality control scheme /schedule in your lab

2.To identify the Quality control charts and quality control roles

3.To identify the new rules of west guard.

4. Overview of the CLSI guide lines C24.

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FIRST OBJECTIVE

To determine how to establish the analytical goal and quality control !

scheme /schedule in your lab

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Data we needed to design Quality Control

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1.Commercial QC material

2.Manufacturers’ kit inserts .

3. Doing it for yourself is, as usual, the safest method.

4.EQAS programs .

Designing the internal quality control protocol

1.Define the level of quality that the laboratory wants to attain for a determined test (the analytical quality

specification.(

2 .know the stable analytical performance for this test.

3 .a control rule (control limits and number of controls per run).

4 .Assure quality of results:

a. analytical imprecision and bias

b. EQAS

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Proficiency testing

# Inter laboratory Comparison Programs Help Improve Laboratory Performance.

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Define Analytical Goal

Two main strategies for analytical quality specifications based on

calculation of imprecision and bias.

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How to establish your analytical goal?

*The underlying principle of ‘measurement uncertainty’ is that a laboratory should know how precisely they can measure any particular analyte.

*Two main strategies for analytical quality specifications based on biology have been evaluated for imprecision and bias (in combination with imprecision), respectively

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Challenges to set analytical Goal

ExternalInternal

Permenant

Method:Implementation:

Analytical principleChoice of conditions

Equipment'In house' equipment

Reagents'In house' reagents,

)choice of producer(Time, Temperature, Volume, etc.

Standardization:Standardization:

Traceability of calibrationCalibration function

VariableBatches:Performance:

Reagents (variability)'in house' reagents

CalibratorsTraining, Maintenance, etc.

ConsumablesControl with 'trouble-shooting'

Documentation

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ExternalInternal

Permenant

Method:Implementation:

Analytical principleChoice of conditions

Equipment'In house' equipment

Reagents'In house' reagents,

)choice of producer(Time, Temperature, Volume, etc.

Standardization:Standardization:

Traceability of calibrationCalibration function

VariableBatches:Performance:

Reagents (variability)'in house' reagents

CalibratorsTraining, Maintenance, etc.

ConsumablesControl with 'trouble-shooting'

Documentation

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Relevance to customers

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All these complicated processes to provide the appropriate quality for our patient cares

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Setting Goals For Q.C Performance

1.Maximum allowable number of unacceptable results, due to an out of control error conditions.2.Maximum allowable probability of reporting unacceptable results.3.Minmum acceptable probability of detecting an out of control error condition.4.Maximum acceptable probability of false rejection. *Main aim is to Maximize probability to detect an out of control condition for measurement procedure , while minimize probability for false Q.C alerts.

Analysis of Control Materials

A stable control which mimics patient’s sample is analyzed (DAY TO DAY OR SET TO SET)

Need data set of at least 20 points, obtained over a 30 day period

Calculate mean, standard deviation, coefficient of variation; determine target ranges

CLIA proficiency testing criteria for acceptable analytical performance:

Objective

2.To identify the Quality control charts and quality control roles

3.To identify the new rules of west guard.

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Monitoring QC Data

Develop Levey-Jennings chart.

Plot control values each run, make decision regarding acceptability of run.

Monitor over time to evaluate the precision and accuracy of repeated measurements

Review charts at defined intervals, take necessary action, and document

Levey-Jennings Chart

A graphical method for displaying control results and evaluating whether a procedure is in-control or out-of-control

Control values are plotted versus time

Lines are drawn from point to point to accent any trends, shifts, or random excursions

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Levey-Jennings Chart

The Levey-Jennings chart usually has the days of the month plotted on the X-axis and the control observations plotted on the Y-axis. On the right is the Gaussian or "bell-shaped" curve turned on its side to show the correlation of the curve to the chart (ie, fewer data points should appear on the upper and lower extremities of the chart, since the "bell" is thinner farther from the mean). By observing the data plotted in the L-J chart, we can determine if test results are in control and accurate, or if test results are not in control and consequently unacceptable. .

Levey-Jennings Chart Calculate the Mean and Standard Deviation;Record the Mean and +/- 1,2 and 3 SD Control Limits

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Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

Levey-Jennings Chart -

Record Time on X-Axis and the Control Values on Y- Axis

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Con

trol

Val

ues

(e.g

. mg/

dL)

Time (e.g. day, date, run number)

Levey-Jennings Chart -Plot Control Values for Each Run

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Cont

rol V

alue

s (e

.g. m

g/dL

)

Time (e.g. day, date, run number)

Levey-Jennings Chart -Record and Evaluate the Control Values

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Mean

Day

+1SD

+2SD

+3SD

-1SD

-2SD

-3SD

UCL

Target= Mean

LCL

Samples

Time

In control Out of control !

Natural variation

Look forassignable cause !

Problem corrected6

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NaturalVariation

“Allows determination of whether an analytical run is “in-control” or “out-of-control”

Westgard Rules are a multi role QC procedure

1-West-gard rules: (Regular twice entry for Q.C)

1 3s, 1 2s, 2 2s , R 4s, 4 1s, 10x (& modifications 8x, 12x)

 

2-Recent west-gard rules, fit better and are easier to apply in situations where 3 different control materials are being analyzed:

2of3 2s, 3 1s, 6x & 9x

3-A related control rule that is sometimes used looks for a "trend:"

7T

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Westgard Rules are a multirule QC procedure

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13s refers to a control rule that is commonly used with a Levey Jennings chart .

A run is rejected when a single control measurement exceeds the mean plus 3s or the mean minus 3s control limit.

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12s refers to the control rule that is commonly used with a Levey-Jennings chart single control measurement exceeds the mean plus 2s or the mean minus 2s control limit .

This rule is used as a warning rule to trigger careful inspection of the control data by the following rejection rules.

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22s - reject when 2 consecutive control measurements exceed the same mean plus 2s or the same mean minus 2s control limit .

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R4s - reject when 1 control measurement in a group exceeds the mean plus 2s and another exceeds the mean minus 2s .

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41s - reject when 4 consecutive control measurements exceed the same mean plus 1s or the same mean minus 1s control limit .

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10x - reject when 10 consecutive control measurements fall on one side of the mean .

some modifications: 8x - reject when 8 consecutive control measurements fall on one side of the mean 12x - reject when 12 consecutive control measurements fall on one side of the mean .

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In situations where 3 different control materials are being analyzed, some other control rules fit better and are easier to apply, such as:2of32s - reject when 2 out of 3 control measurements exceed the same mean plus 2s or mean minus 2s control limit

;

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31s - reject when 3 consecutive control

measurements exceed the same mean plus 1s or mean minus 1s control limit.

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some modification:6x - reject when 6 consecutive control measurements fall on one side of the mean.

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A related control rule that is sometimes used, looks for a "trend" where several control measurements in a row are increasing or decreasing 7T - reject when seven control measurements trend in the same direction, i.e., get progressively higher or progressively lower.

there are two types of errors, random and systematic

the multirule combines the use of two types of rules to help detect those two types of errors.

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Corrective action

1- Determine the type of error occurring on the basis of the rule violated.

2-Refer to trouble-shooting guides to identify possible causes for the type of error indicated by the control rule that was violated.

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Type of Error Control rule that detects it

Random error13s, R4s

Systematic error2 2s, 4 1s, 2of3 2s, 3 1s, 6x, 8x, 9x, 10x, 12x, cusum

There are two types of errors, random and systematic the multi rule combines the use of two types of rules to help detect those two types of errors:

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3 -Correct the problem, then analyze control samples again to assess control status.

4- Repeat or verify the results on the patient samples once the method has been demonstrated to be in-control.5- Consult a supervisor for any decision to report patient results when a run is out-of-control.

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Overview of the CLSI guide lines C24.

OBJECTIVE

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Who is CLSI?

Clinical and Laboratory Standards Institute •ANSI-accredited, global, nonprofit standards

development organization •CLSI has over 2,000 members – organizations such

as IVDmanufacturers, hospital laboratories, reference laboratories, universities,

professional associations, and government agencies

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CLSI –C24:Q.C planning process

1.Define Quality requirement inn the form of Allowable total error.

2.Select suitable Q.C material.3.Obtain estimates of methods of impersion and bias

4.Identify traditional control rules.5.Predict performance in terms of probabilities for

rejection (including false rejection),through the available charts/graphs.

6.Set goals for Q.C performance as probability of error detection of 90%,and a probability of false rejection of 5% chance.

7.Detect critical systemic errors using suitable graphical tools.

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Calculating Sigma Level of critical systemic error

Critical systemic error= ) [total allowable error - Bias

mean)/Impercision]%

SIGMA-METRIC= Critical systemic error + 1.65

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Laboratory Quality Control Based on Risk Management—Proposed Guideline

guidance to enable labs to develop effective, cost-efficient QC protocols to:

-Reduce negative impact of test system’s limitations.

-Monitor immediate and extended test performance.

CLSI EP23 Guideline

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For each risk, a mitigation strategy is found that will reduce the residual risk to an acceptable level.

Sum of all QC elements (manufacturer provided and laboratory added) becomes the laboratory’s QC plan specific to this device and the laboratory environment.

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Doesn’t replace surrogate QC, but incorporates surrogate QC to address the potential for certain risks

Utilizes a risk management approach to developing a customized QC plan.

Provides a scientific basis for justifying QC strategies (useful for lab inspectors)

CLSI EP23 Guideline