Download What is Quality Control?

ANALYTICAL PROCESS
CONTROL
QC for QUALITATIVE TESTS
John Elliot
WHO Collaborating Centre
PPTC, Wellington, NZ
Laboratory Sections
that use
Qualitative Tests
• Microbiology
• Blood Transfusion
• Infectious Diseases Serology
PPTC, Wellington, NZ
INTERNAL QUALITY CONTROL
(IQC)
IQC REFERS TO THE SET OF PROCEDURES
UNDERTAKEN BY THE LABORATORY
STAFF FOR THE
CONTINUOUS AND IMMEDIATE
MONITORING OF LABORATORY WORK IN
ORDER TO DECIDE WHETHER THE
RESULTS ARE RELIABLE ENOUGH TO BE
RELEASED.
PPTC, Wellington, NZ
What is IQC?
• The regular testing of quality control [QC]
material along with the patient samples
• Comparison of the QC results to specific
statistical limits [ranges]
• Rejection of patient results if QC is outside of
limits
But does this apply to qualitative tests?
If not, Why not?
PPTC, Wellington, NZ
WHAT IS THE MOST COMMON
LABORATORY ERROR?
TRANSCRIPTION
Not technical
PPTC, Wellington, NZ
Microbiology Quality Control
Accuracy and clinical value of results
depend on:
• Quality of specimen
• Validity of test method
• Performance of test procedure, reagents and
media
• Reports and interpretation
• Staff
• Equipment
PPTC, Wellington, NZ
In Microbiology how do we QC
• The Quality of the specimen
• The Performance of test procedures,
reagents and media
PPTC, Wellington, NZ
1. Specimen
• Appropriate specimen
• Collection method
• Delivery system
PPTC, Wellington, NZ
Gram Stain
PPTC, Wellington, NZ
PPTC, Wellington, NZ
PPTC, Wellington, NZ
IDENTIFICATION SYSTEM
PPTC, Wellington, NZ
2. Specimen Processing:
Test Methods
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Staining and Microscopy
Culture Media
Incubation
Organism Identification
Antimicrobial Susceptibility Testing
PPTC, Wellington, NZ
Culture Media:
Both Solid and Liquid
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Dating when received and when opened
Weighing
Dissolving
Sterilizing
Storage of prepared media
Addition of enrichments [eg Blood]
Sterility Testing
Incubation of inoculated media
PPTC, Wellington, NZ
QC of Media
• Agar Plates
» Haemolysis controls
» Selective media controls
• Liquid broths
» Positive and negative reactions
–
Therefore Stock Cultures
PPTC, Wellington, NZ
Stock QC organisms
• Organisms to be maintained must be
adequate to check all media and test
systems.
– E. coli – MacConkey, XLD, susceptibility
tests
– Staphylococcus aureus – Blood agar,
Mannitol Salt, susceptibility tests
– Neisseria gonorrhoeae – chocolate,
Thayer-Martin
PPTC, Wellington, NZ
QC of Stains and Reagents
• Gram stain QC
– Use gram positive and gram negative organisms
to check regularly [at least once a week]
• ZN QC
– Use positive and negative AFB slide with every
batch stained.
• Other Stains
– Check as used – positive and negative reactions
• Reagents
– Check as used with known positives and
negatives.
PPTC, Wellington, NZ
Temperature Chart:Incubator
PPTC, Wellington, NZ
Temperature Chart: Refrigerator
PPTC, Wellington, NZ
Antimicrobial Susceptibility
Testing
• Storage of antibiotic disks
• Correct concentration of antibiotic in disk
• Joan Stokes Method
• NCCLS Method
– Detailed QC Procedures to ensure reproducability of results
– Depth of agar!!
PPTC, Wellington, NZ
Antimicrobial
Susceptibility
Testing
PPTC, Wellington, NZ
Detecting Errors
• Many organisms have predictable
antimicrobial test results
– Staphylococcus spp. are usually susceptible
to vancomycin
– Streptococcus pyogenes are always
susceptible to penicillin
– Klebsiella pneumoniae are resistant to
ampicillin
PPTC, Wellington, NZ
Sources of Error
• If you encounter an unusual pattern
– rule out error by checking identification of
organisms
– repeat antimicrobial susceptibility test
• Report if repeat testing yields same result, or
refer the isolate to a reference laboratory for
confirmation
PPTC, Wellington, NZ
QC in Blood Transfusion
Service
PPTC, Wellington, NZ
Blood Transfusion Service
Blood Bank
Recipients
Donors
Safety Precautions
Recruit – Screen – Bleed
test – process – Xmatch
transfuse – follow up
PPTC, Wellington, NZ
QC in Blood Bank Technology
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Donor services
Blood grouping
Crossmatch & antibody screening
Transfusion
PPTC, Wellington, NZ
QC in Blood Bank
• Positive and negative controls on all
tests
• Reverse grouping
• Good documentation, SOPs etc
• Equipment monitoring, calibration,
maintenance
PPTC, Wellington, NZ
QC of Rapid Tests for Infectious Diseases
PPTC, Wellington, NZ
Infectious Diseases Serology
QC of Rapid Methods
• IQC
• Positive controls
• Negative controls
» How often?
» Where do you get the controls from?
PPTC, Wellington, NZ
PPTC, Wellington, NZ
Qualitative vs.Quantitative
• Quantitative test
– measures the amount of a substance
present
• Qualitative test
– determines whether the substance being
tested for is present or absent
PPTC, Wellington, NZ
What is Quality Control?
• Process or system for monitoring the
quality of laboratory testing, and the
accuracy and precision of results
• Routinely collect and analyze data from
every test run or procedure
• Allows for immediate corrective action
PPTC, Wellington, NZ
Designing a QC Program –
• Establish written policies and
procedures
– Corrective action procedures
• Train all staff
• Design forms
• Assure complete documentation and
review
PPTC, Wellington, NZ