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

1. Specimen

• Appropriate specimen

• Collection method

• Delivery system

PPTC, Wellington, NZ

Gram Stain

PPTC, Wellington, NZ

PPTC, Wellington, NZ

PPTC, Wellington, NZ

IDENTIFICATION SYSTEMIDENTIFICATION SYSTEM

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

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

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

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