hiv testing quality assurance and quality control
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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 - PowerPoint PPT PresentationTRANSCRIPT
HIV Testing Quality Assurance and Quality Control
Eligius Lyamuya MD, MMed, PhDDepartment 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
Requirements for Laboratory diagnosis of HIV infection
• Standard Laboratory facilitySuitable physical structureWell equipped with essential facilities
• Human resourcesWell trainedAdequate number
• Test kitsAcceptable qualityConstant supply
• Financial resources• Quality management
Diagnosis of HIV/AIDS
• Clinical criteriaWHO and CDC criteria
• Laboratory TechniquesIsolation of the virus in cultureDetection of viral antigens e.g. p24 agDetection of viral nucleic acid by
polymerase chain reaction (PCR)Detection of specific antibody to HIV
antigens
HIV Testing
• Antibody testsEnzyme-Linked Immunosorbent Assays (EIA) Western BlotRapid tests
• Antigen testsEIA P24 tests
• Nucleic acid detection by Polymerase Chain Reaction (PCR)
Time from Infection to Detection of HIV-1 Markers
5 10 15 20 25 30 35
Antibody assays
p24
DNA PCR
RNA PCR
Detection of HIV: Days after infection
KEY:
EARLIEST POSSIBLE DETECTION OF HIV
NO DETECTION
HIV diagnosis in Adults and Children >18 months
• Antibody-based tests (detection)• Most commonly used assays:
• 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:– Skilled lab technician – Availability of reader, washer, incubator– Properly maintained equipment required– Power– Ideal for large volume testing
HIV Testing – Rapid Tests
• 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 strategyTest objective: surveillance, blood screening,
diagnosisSensitivity 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 IRequires one testFor diagnosis where prevalence among
persons with clinical signs is >30%For surveillance where HIV prevalence is >10%
WHO HIV Testing Strategies-2
• Strategy IIRequires up to two testsFor 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 IIIRequires up to three testsFor diagnosis where prevalence among
asymptomatic is 10%
HIV Testing Strategies
• Serial testing
– Samples tested by a first test– Result of first test determines whether
additional testing is required
• 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 (tie- breaker) 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 SampleBlood Sample
BiolineBioline
Non-reactive Result
Report: Negative
Non-reactive Result
Report: Negative
Reactive ResultReactive Result
DetermineDetermine
Reactive Result
Report: Positive
Reactive Result
Report: Positive
Non-reactiveResult
Non-reactiveResult
Non-reactive Result
Report: Negative
Non-reactive Result
Report: Negative
Reactive Result
Report: Positive
Reactive Result
Report: Positive
UnigoldUnigold
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
• 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
Data and Lab Management Safety Customer Service
Data and Lab Management Safety Customer Service
Patient/Client PrepSample CollectionPatient/Client PrepSample Collection
Sample Receipt and AccessioningSample Receipt and Accessioning
Record KeepingRecord Keeping
ReportingReporting
Personnel CompetencyTest EvaluationsPersonnel CompetencyTest Evaluations
TestingTesting
Sample TransportSample Transport
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 System
• Organizational structure, resources, processes and procedures needed to implement quality management
Quality System Essentials
• 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
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.