HIV Guideline 2016 - cqihiv.com Forum_Sakchai.pdf · • Anti-HIV Antibody Test • HIV p24 Antigen...
Transcript of HIV Guideline 2016 - cqihiv.com Forum_Sakchai.pdf · • Anti-HIV Antibody Test • HIV p24 Antigen...
HIV Guideline 2016
Sakchai DettrairatDivision of Clinical Immunology
Department of Medical Technology
Faculty of Associated Medical SciencesChiang Mai University
J Clin Virol, Volume 54, Issue 1, May 2012, p42-47
Appearance of HIV markers in early HIV infection
Objectives• Blood and blood products safety.
• Screening of donors of sperms, organs and tissues.
• Diagnosis of HIV infection in clinically suspected cases.
• Voluntary counseling and testing (VCT).
• Epidemiological surveillance.
• Research and surveys.
Diagnosis of HIV Infection
Diagnostic Tests• Anti-HIV Antibody Test
• HIV p24 Antigen Test
• HIV Nucleic AcidAmplification Tests(NAAT)
Screening Tests
EIA/ELISA or CIAs
Simple/Rapid Tests
Confirmatory or Supplemental Tests
WB
IFA
HIV Testing
Generation Antigens/antibodies Comment/characteristic
First Antigens from HIV lysates Lack of sensitivity and specificity
Second Recombinant proteins and/or synthetic peptides
Improved sensitivity andproduction of combined HIV-1/HIV-2 assays
Third Use labeled antigen asconjugate
Very high sensitivity and able to detect IgM Ab; reduced the window period considerably
Fourth Detection of both HIV antigen (p24) and Ab
Further reducing the window period
Generation of anti-HIV EIAs
rHIV Ag and synthetic peptides
Enzyme conjugated HIV Ag
IgG AbIgM Ab
Substrate Reactive End Product
(color/light)
Env/Core Ags
E E EE
EE
Third generation Double Antigen Sandwich ELISA for detection of HIV Abs
Anti-p24 AbrHIV Ag/ peptide
Enzyme-conjugatedAnti-p24 Ab
p24 Ag
Enzyme conjugated HIV Ag
Anti-HIV Ab
Substrate Reactive End Product
(color/light)
EE
E EE
E
Fourth generation Sandwich ELISAfor detection of both HIV Ag and Abs
Lateral flow strip
• Qualitative test to detect Abs
to HIV-1/2
• Simple or Moderate Complexity
• Serum/Plasma/Whole blood
• Visual Reading in 10-15 min
• Testing formats
– Immunofilteration (flow through)
– Immunochromatography
(lateral flow)
– Dot immunoassay,
– Particle agglutination
Rapid HIV Tests
HIV Immunochromatographic Test (Lateral Flow Strip)
• Tests for screening of blood and blood
products
–Sensitivity 100%
–Specificity > 99.5%
• Tests for individual diagnosis
–Sensitivity > 99.5%
–Specificity > 99%
Sensitivity and Specificity of HIV tests
• Diagnostic Sensitivity
–The ability of the test to identify
correctly those who have the disease
• Diagnostic Specificity
–The ability of the test to identify
correctly those who do not have the disease
Sensitivity & Specificity
Test Parameter
Interpreting HIV Test Results
Assay 1 Assay 2 Assays 1+2 (in sequence)
Sensitivity 99.0% 99.0%
Specificity 99.5% 99.9%
Prevalence PPV PPV PPV
0.2% 28.4% 66.4% 99.75%
2.0% 80.2% 80.2% 99.97%
20.0% 98.0% 99.6% 99.99%
PPV & Prevalence
Sensitivity = 99.5%, Specificity = 99%PPV = 81.59/180.77 = 45.135%
NPV = 9,818.82/9,819.23 = >99.99%
HIV
InfectionNo HIV Infection
Positive results
81.59 99.18 180.77
Negative results
0.41 9,818.82 9,819.23
Prevalence0.82%
82 9,91810,000
(population)
PPV & NPV of HIV Testing
Prevalence(%)
%PPV:
1 test
%PPV:
2 tests
%PPV:
3 tests
%NPV
0.05 4.7415 83.2000 99.7975 99.9997
0.5 33.3333 98.0296 99.9798 99.9975
0.82 45.1347 98.7930 99.9877 99.9958
2.0 67.0034 99.5075 99.9950 99.9897
5.0 83.9662 99.8085 99.9981 99.9734
10.0 91.7051 99.9092 99.9991 99.9439
PPV and NPV of HIV Testing Strategies at Different Prevalence Rates
• UNAIDS and WHO Recommended Alternative HIV
Testing Strategies (1997)
• Thailand HIV Testing Algorithms (2013)
• CDC Laboratory testing for the Diagnosis of HIV
Infection: Updated Recommendation (2014)
• WHO New Guidelines on HIV Testing (2015)
• Thailand Update Guideline for HIV Testing (2016)
HIV Testing Strategies/Algorithms
http://thaiaidssociety.org/index.php?option=com_content&view=article&id=79&Itemid=86
Tests for individual diagnosis
– Sensitivity > 99.5%– Specificity > 99%
Thailand HIV testing algorithm for individual diagnosis (2013)
Anti-HIV negative
A1+ (R)
A2
Repeat A1 and A2
A1+, A2+
A1+, A2+, A3+
Anti-HIV PositiveRetest sample 2
Inconclusive
A1+, A2+, A3-
Retest at 2 weeks and/or 1 month and 3 months
A1
A3
A1-, A2-
A1+, A2- A1+, A2+
A1+, A2-
A1- (NR)
HIV testing Algorithms in Adults and Children >18 M
HIV testing Algorithms in Children <18 M
http://www.cdc.gov/hiv/pdf/HIVtestingAlgorithmRecommendation-Final.pdf
Published June 27, 2014
Recommended Laboratory HIV Testing Algorithm for Serum or Plasma Specimens
• More accurate laboratory diagnosis of acute HIV-1 infection,
• Equally accurate laboratory diagnosis of established HIV-1 infection,
• more accurate laboratory diagnosis of HIV-2 infection,
• fewer indeterminate results, and
• Faster turnaround time for most test results.
The recommended algorithm has several advantages
http://www.who.int/hiv/en/
WHO New Guidelines on HIV Testing (2015)
http://apps.who.int/iris/bitstream/10665/179870/1/9789241508926_eng.pdf?ua=1&ua=1
HIV inconclusive 1. A1+A2-A3+ or2. A1+A2-A3-If A1 is 4th gen assay
Retest in 14 days
Testing strategy for HIV diagnosis in high prevalence settings (≥ 5%)
HIV inconclusive 1. A1+A2+A3- or2. A1+A2-If A1 is 4th gen assay
Retest in 14 days
Testing strategy for HIV diagnosis in low prevalence settings (<5%)
WHO recommends retesting to assure
accurate diagnosis in three instances:
1. retesting people who test HIV-negative but
are at on-going risk for HIV;
2. retesting people with an HIV inconclusive
status after 14 days; and
3. retesting to verify an HIV-positive diagnosis
before enrolling in care and/or starting antiretroviral therapy (ART)
When to retest?
?
Thailand Update Guideline for HIV Testing (2016)
Inconclusive: Retest at 2 weeks and 1 month
HIV testing Algorithms in Adults and Children >24 Months
HIV testing Algorithms in Children <24 Months
No diagnostic test or algorithm can be completely accurate in
all cases of HIV infection.