pptc, wellington, nz analytical process control qc for qualitative tests john elliot who...
TRANSCRIPT
PPTC, Wellington, NZ
ANALYTICAL PROCESS ANALYTICAL PROCESS CONTROLCONTROL
QC for QUALITATIVE TESTS
John ElliotWHO Collaborating Centre
PPTC, Wellington, NZ
Laboratory Sectionsthat use
Qualitative Tests
• Microbiology
• Blood Transfusion
• Infectious Diseases Serology
PPTC, Wellington, NZ
INTERNAL QUALITY CONTROL INTERNAL QUALITY CONTROL (IQC)(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?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 WHAT IS THE MOST COMMON LABORATORY ERROR?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
2. Specimen Processing:Test Methods
• Staining and Microscopy
• Culture Media
• Incubation
• Organism Identification
• Antimicrobial Susceptibility Testing
PPTC, Wellington, NZ
Culture Media:Both Solid and Liquid
• 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
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
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
Donors Recipients
Safety Precautions
Recruit – Screen – Bleed test – process – Xmatch transfuse – follow up
Blood Transfusion ServiceBlood Bank
PPTC, Wellington, NZ
QC in Blood Bank Technology
• 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
Infectious Diseases Serology QC of Rapid Methods
• IQC• Positive controls• Negative controls
» How often?» Where do you get the controls from?
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