unit #7 - basic quality control for the clinical laboratory cecile sanders, m.ed., mt(ascp), cls...

Unit #7 - Basic Quality Unit #7 - Basic Quality Control for the Clinical Control for the Clinical

LaboratoryLaboratory

Cecile Sanders, M.Ed., Cecile Sanders, M.Ed., MT(ASCP), MT(ASCP),

CLS (NCA)CLS (NCA)

Unit #7 - Basic Quality Control Unit #7 - Basic Quality Control for the Clinical Laboratoryfor the Clinical Laboratory

IntroductionIntroduction– The results obtained from The results obtained from

laboratory analyses are used to laboratory analyses are used to diagnose, prescribe treatment, diagnose, prescribe treatment, and/or monitor the health or and/or monitor the health or progress of the patient. Since such progress of the patient. Since such importance is placed upon test importance is placed upon test results, they must be as reliable results, they must be as reliable and accurate as possible.and accurate as possible.


Elements of a Total Quality Control Elements of a Total Quality Control Program (may be referred to as QC, Program (may be referred to as QC, QA, or TCM, among others)QA, or TCM, among others)– Current procedure manualCurrent procedure manual– DocumentationDocumentation– Qualified personnelQualified personnel– Fire and safety programFire and safety program– Use of appropriate standards and Use of appropriate standards and

controlscontrols– External proficiency testingExternal proficiency testing


Standards and ControlsStandards and Controls– StandardStandard

A substance that has an exact known value and A substance that has an exact known value and that, when accurately weighed or measured, can that, when accurately weighed or measured, can produce a solution of an exact concentrationproduce a solution of an exact concentration

Also called “reference materials”Also called “reference materials” Not usually used on a daily basisNot usually used on a daily basis Used to calibrate new instruments, recalibrate Used to calibrate new instruments, recalibrate

instruments after repair, at manufacturer’s instruments after repair, at manufacturer’s recommended intervals, or if a method is out of recommended intervals, or if a method is out of controlcontrol


– ControlControlA solution that contains the same A solution that contains the same

constituents as those being analyzed in the constituents as those being analyzed in the patient samplepatient sample

Most are commercially produced from Most are commercially produced from pooled serapooled sera

The manufacturer has analyzed each lot of The manufacturer has analyzed each lot of serum for a variety of test components and serum for a variety of test components and the expected range of assay values for each the expected range of assay values for each component is provided to the laboratory component is provided to the laboratory when shippedwhen shipped


– Control (cont’d)Control (cont’d)Controls are analyzed with each patient test Controls are analyzed with each patient test

or batch of tests and the results are or batch of tests and the results are compared with the manufacturer’s range of compared with the manufacturer’s range of valuesvalues

For most tests, a “normal” control and an For most tests, a “normal” control and an “abnormal” control are analyzed with each “abnormal” control are analyzed with each patient test or batch of testspatient test or batch of tests

Results are plotted on a QC record called a Results are plotted on a QC record called a Levey-Jennings Chart Levey-Jennings Chart


Example of Levey-Jennings ChartExample of Levey-Jennings Chart


Accuracy - closeness of a result to Accuracy - closeness of a result to the actual valuethe actual value

Precision – “reproducibility” or Precision – “reproducibility” or closeness of values to each othercloseness of values to each other


Mean, Variance and Standard Mean, Variance and Standard Deviation – these must be determined Deviation – these must be determined for each test or analysis to be used for for each test or analysis to be used for quality controlquality control– Mean ( ) = the average for a set of Mean ( ) = the average for a set of

valuesvalues– Standard Deviation (Standard Deviation (s s or SD) = a measure or SD) = a measure

of the scatter of the sample values of the scatter of the sample values around the mean and is derived from the around the mean and is derived from the calculation of the variance (calculation of the variance (ss22))


– Calculating the Calculating the variancevariance


Using Standard Using Standard Deviation in QCDeviation in QC– When a set of values When a set of values

with a normal with a normal distribution is distribution is plotted on a graph, plotted on a graph, the distribution of the distribution of the values around the values around the mean forms a the mean forms a Gaussian Curve (also Gaussian Curve (also known as a normal known as a normal frequency or normal frequency or normal distribution curve)distribution curve)


Using Standard Deviation in QC Using Standard Deviation in QC (cont’d)(cont’d)– Clinical laboratories establish the Clinical laboratories establish the

standard deviation for each laboratory standard deviation for each laboratory test or analysistest or analysis

– A common choice is plus or minus 2 A common choice is plus or minus 2 s s or or SD, most often written as ± 2 SD, most often written as ± 2 s s or ± 2 or ± 2 SDSD


– The mean and ± 2 The mean and ± 2 SD are plotted on a SD are plotted on a Levey-Jennings Levey-Jennings chart (green line is chart (green line is ))


Every time the control is run, the value Every time the control is run, the value is plotted on the L-J chartis plotted on the L-J chart


As long as the control value are between the As long as the control value are between the ± 2 SD lines on the L-J chart (in this case, the ± 2 SD lines on the L-J chart (in this case, the lines are colored yellow), the control values lines are colored yellow), the control values are “in control”are “in control”


On the L-J chart below, note that values for On the L-J chart below, note that values for days 5, 8, 11, 17, 25, and 27 are outside the days 5, 8, 11, 17, 25, and 27 are outside the ± 2 SD yellow lines. Therefore, controls on ± 2 SD yellow lines. Therefore, controls on these days are “out of control”these days are “out of control”


Levey-Jennings Levey-Jennings Chart with Values Chart with Values “In Control”“In Control”

Levey-Jennings Chart Control Range 80-100

80

85

90

95

100

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

Days or Runs

Co

ntr

ol

Val

ues


Trend Trend – An uninterrupted An uninterrupted

rise or decline away rise or decline away from the mean from the mean

– When the 6When the 6thth value value with a rise or with a rise or decline is reached, decline is reached, the values are “out the values are “out of control”of control”


Showing Trend 5 through 10

80

90

100

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

Days or RunsC

on

tro

l Va

lue

s


ShiftShift– An uninterrupted An uninterrupted

shift of values on shift of values on one side of the one side of the meanmean

– When the 6When the 6thth value value on one side of the on one side of the mean is reached, mean is reached, the values are “out the values are “out of control”of control”


Showing Shift 5 through 10

80859095100

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

Days or Runs

Co

ntr

ol

Val

ues


The use of a single control is for very basic The use of a single control is for very basic laboratory testing in waived CLIA laboratorieslaboratory testing in waived CLIA laboratories

In moderately and highly complex CLIA In moderately and highly complex CLIA testing laboratories two controls (usually a testing laboratories two controls (usually a “normal” and an “abnormal”) must be run “normal” and an “abnormal”) must be run with each test or batch of tests and Westgard with each test or batch of tests and Westgard Rules applyRules apply

Westgard Rules are beyond the scope of this Westgard Rules are beyond the scope of this course and will be covered in advanced MLT course and will be covered in advanced MLT coursescourses

http://www.westgard.com/mltirule.htmhttp://www.westgard.com/mltirule.htm


Whenever a patient’s test or a batch of Whenever a patient’s test or a batch of tests are performed and the control(s) is tests are performed and the control(s) is “in control”, the values obtained for the “in control”, the values obtained for the patient test(s) are determined to be patient test(s) are determined to be “acceptable” and can be released to the “acceptable” and can be released to the doctor as accurate.doctor as accurate.

Whenever a patient’s test or a batch of Whenever a patient’s test or a batch of tests are performed and the control(s) is tests are performed and the control(s) is “out of control”, the values obtained for “out of control”, the values obtained for the patient test(s) are determined to be the patient test(s) are determined to be “not acceptable” and CANNNOT be “not acceptable” and CANNNOT be released to the doctor as accurate until released to the doctor as accurate until the problem is identified and resolved.the problem is identified and resolved.


Errors in Laboratory TestingErrors in Laboratory Testing– May occur at several points May occur at several points

Preanalytical – errors made prior to testing the Preanalytical – errors made prior to testing the patient specimen (Ex. Misidentifying the patient patient specimen (Ex. Misidentifying the patient during blood collection, mishandling specimen, during blood collection, mishandling specimen, etc.)etc.)

Analytical – errors made in the testing process Analytical – errors made in the testing process (Ex. Error in procedure, instrument trouble, etc.)(Ex. Error in procedure, instrument trouble, etc.)

Postanalytical – errors made after testing (Ex. Postanalytical – errors made after testing (Ex. Typing the wrong results in the computer, failure Typing the wrong results in the computer, failure to notify physician in a timely manner, etc.)to notify physician in a timely manner, etc.)


Errors in Laboratory Testing (cont’d)Errors in Laboratory Testing (cont’d)– Random or SystematicRandom or Systematic

Random Errors – cannot be absolutely Random Errors – cannot be absolutely identified (Ex. Differences in techniques identified (Ex. Differences in techniques between workers, specimen characteristics, between workers, specimen characteristics, etc.)etc.)

Systematic Errors – variation that may make Systematic Errors – variation that may make results consistently higher or lower than the results consistently higher or lower than the mean value for a control (Ex. Trouble with mean value for a control (Ex. Trouble with the instrument, deteriorated reagents, etc.)the instrument, deteriorated reagents, etc.)


Errors in Errors in Laboratory Testing Laboratory Testing (cont’d)(cont’d)– Our goal is to Our goal is to

identify systematic identify systematic errors and eliminate errors and eliminate them!them!

My control results My control results are “out of are “out of control”! Now control”! Now what?what?


The following steps should be taken in order The following steps should be taken in order when the control results are “out of control”when the control results are “out of control”

1.1. Look at the procedure and evaluate your Look at the procedure and evaluate your technique (Ex. Did I use the right lot #? Are my technique (Ex. Did I use the right lot #? Are my reagents in date? Did I make an error in the reagents in date? Did I make an error in the procedure?) procedure?)

2.2. Re-run the procedure, including controlsRe-run the procedure, including controls

3.3. If results are still out of control, clean/perform If results are still out of control, clean/perform maintenance on equipment and/or open a new maintenance on equipment and/or open a new batch of reagentsbatch of reagents

4.4. Contact supervisorContact supervisor


ALWAYS, ALWAYS, ALWAYS, ALWAYS, ALWAYS: ALWAYS:

DOCUMENT THE DOCUMENT THE PROBLEM AND PROBLEM AND CORRECTIVE CORRECTIVE

ACTIONS ACTIONS TAKEN!!!!!TAKEN!!!!!


Click on the “Assignments” button Click on the “Assignments” button on the lower left of the menu for the on the lower left of the menu for the assignment for this unit.assignment for this unit.

Remember this is an ASSIGNMENT, Remember this is an ASSIGNMENT, so you may use all instructional so you may use all instructional materials to complete the materials to complete the assignment, including this assignment, including this PowerPoint.PowerPoint.

unit #7 - basic quality control for the clinical laboratory cecile sanders, m.ed., mt(ascp), cls...

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