HIV Testing Quality Assurance
and Quality Control
Eligius Lyamuya MD, MMed, PhD
Department of Microbiology and Immunology
Muhimbili University of Health and Allied
Sciences
Disposition
• HIV Diagnosis
• HIV Testing techniques
– Tests
– Strategies
– Algorithms
• Quality Issues
– Quality management
• QC
• QA
• Quality improvement
– Quality system
HIV Diagnosis
Requirements for Laboratory diagnosis of
HIV infection
• Standard Laboratory facility
 Suitable physical structure
 Well equipped with essential facilities
• Human resources
 Well trained
 Adequate number
• Test kits
 Acceptable quality
 Constant supply
• Financial resources
• Quality management
Diagnosis of HIV/AIDS
• Clinical criteria
WHO and CDC criteria
• Laboratory Techniques
Isolation of the virus in culture
Detection of viral antigens e.g. p24 ag
Detection of viral nucleic acid by
polymerase chain reaction (PCR)
Detection of specific antibody to HIV
antigens
HIV Testing Techniques
HIV testing Campaign in Tanzania
08/04/2015
7
HIV Testing
• Antibody tests
Enzyme-Linked Immunosorbent Assays (EIA)
Western Blot
Rapid tests
• Antigen tests
EIA P24 tests
• Nucleic acid detection by
Polymerase Chain Reaction (PCR)
Time from Infection to Detection of
HIV-1 Markers
NO DETECTION
KEY:
EARLIEST POSSIBLE DETECTION OF HIV
Antibody
assays
p24
DNA PCR
RNA PCR
5
10
15
20
25
30
Detection of HIV: Days after infection
35
HIV diagnosis in Adults and
Children >18 months
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Antibody-based tests (detection)
Most commonly used assays:
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ELISA
Rapid Tests
Western Blot
HIV Diagnosis in Children <18 months
• Antibody detection cannot be used due to
presence of maternal antibodies
• p24 antigen detection test is used
• HIV nucleic acid (DNA or RNA) detection
by PCR
HIV Testing - ELISA
• Quantitative assay to measure HIV
antibodies
• Some assays can detect both HIV
antibody and HIV antigen (reduce window
period)
• Issues:
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Skilled lab technician
Availability of reader, washer, incubator
Properly maintained equipment required
Power
Ideal for large volume testing
HIV Testing – Rapid Tests
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Qualitative assays to detect HIV antibodies
Most detect both HIV 1 and HIV 2
As reliable as ELISA
Provide same-day results
Do not require additional equipment
• Issues:
– Small volumes
– Validation of use
– Appropriate training
Testing Strategies
• Testing approach used to meet a specific need,
such as:
– Blood Safety
– Surveillance
– Diagnosis
WHO HIV Testing Strategies: Criteria
• Criteria for choosing HIV testing strategy
Test objective: surveillance, blood screening,
diagnosis
Sensitivity and specificity of the test(s)
HIV prevalence in the population
NB:
The HIV test strategy must be validated for use
by each country
WHO HIV Testing Strategies-1
• Strategy I
Requires one test
For diagnosis where prevalence among
persons with clinical signs is >30%
For surveillance where HIV prevalence is >10%
WHO HIV Testing Strategies-2
• Strategy II
Requires up to two tests
For diagnosis where prevalence among
persons with clinical signs is 30% or >10%
among asymptomatic persons
For surveillance where HIV prevalence is 10%
WHO HIV Testing Strategies-3
• Strategy III
Requires up to three tests
For diagnosis where prevalence among
asymptomatic is 10%
HIV Testing Strategies
• Serial testing
– Samples tested by a first test
– Result of first test determines
additional testing is required
whether
• Parallel testing
– Samples are tested simultaneously by two
different tests
Testing Algorithm
• The combination and sequence of specific tests
used in a given strategy
• An HIV Positive status is based upon the
outcome of 2 or more tests
• When two test results disagree (one is reactive,
the other non-reactive), the finding is called
“indeterminate.” In this case, a third test (tiebreaker) must be performed
HIV testing algorithms
• EIA screen followed by Western blot confirmation
• Multiple EIAs screen and confirmation
• Multiple rapid tests screen and confirmation
UNAIDS, WHO and CDC have recommended and
set guidelines for the use of HIV tests in
screening and confirmatory algorithms
Current National HIV Rapid Testing Algorithm
Blood Sample
Bioline
Non-reactive Result
Reactive Result
Report: Negative
Determine
Reactive Result
Non-reactive
Result
Report: Positive
Unigold
Reactive Result
Non-reactive Result
Report: Positive
Report: Negative
Quality Issues
Laboratory quality management
• All activities of the overall management
function that determine quality policy
objectives and implement them within a
system
• Components:
– quality control
– quality assurance
– quality improvement
Quality Control-1
• Operational techniques and activities used
fulfill requirements for quality
– Internal QC: set of procedures for
continuously assessing laboratory work and
emergent results
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running “QC” samples
reading the “control” line
evaluating signal to cutoff ratios for QC samples
having another technologist review test
interpretations, calculations, etc
Quality Control-2
– External QC: of evaluating the performance
of a laboratory in testing samples sent by an
external laboratory
• running proficiency testing samples
• retesting a proportion of samples
Quality Assurance
• A dynamic and ongoing process of
monitoring a system for reliability and
reproducibility of results that permits
corrective action when established criteria
are not met
• Takes into consideration pre-analytical,
analytical and post-analytical phases
The Quality Assurance Cycle
Patient/Client Prep
Sample Collection
Reporting
 Data and Lab
 Management
 Safety
 Customer
 Service
Personnel Competency
Test Evaluations
Sample Receipt and
Accessioning
Record Keeping
Sample Transport
Testing
QA: Pre-analytic
• Select the best test and testing strategy
– which test
– what algorithm
– which laboratories
• Assess testing services before starting testing
• Designate responsibilities and make clear the
decision making process
• Make sure each testing site has reagents and
supplies
• Have standard operating procedures in place
(SOPs)
QA: Analytic
• Provide every testing site with instructions and
training for:
– laboratory safety
– sample receipt (sample assessment and rejection criteria,
logging-in process and forms)
– sample storing
– how to do testing
– how to perform internal QC and external QA and/or proficiency
testing
– how to monitor other testing parameters (e.g., strength of signal
for a QC sample)
• Perform competency checks of laboratory personnel who manage
samples and do testing
– on-site audits
– competency evaluation panels
– review recent proficiency testing data
QA: Post-testing
• Set up a process for evaluating test results
and QC indicators before releasing test
results
• Establish corrective actions to take when
indicators are of control indicators
• Establish a review process to assure
accurate results transcription and reporting
• Store samples properly for retesting and/or
referral
Quality Improvement
• Determination of causes or sources of
problems identified by QC and QA
Quality System
• Organizational structure, resources,
processes and procedures needed to
implement quality management
Quality System Essentials
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Organization
Personnel
Equipment
Purchasing and inventory
Process control
Information management
Documents and Records
Occurrence management
Internal assessment
Process improvement
Service and satisfaction
Facilities and safety
Quality System
Quality Assurance
Quality Control
Take Home Messages
• Not paying attention to QA is like starting a
journey without knowing how to drive, without
doing routine maintenance and without adding
fuel
• If QA and QC is done correctly, troubleshooting
will be a rare event and easy to do
• Laboratories without QC never make mistakes,
because they never detect them
• Even simple tests, require some QA
• The fewer the steps in a process the simpler the
QA.
THANK YOU