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

HIV Diagnosis

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 Techniques

19/04/23 7

HIV testing Campaign in Tanzania

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

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

• 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 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

• 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