Transcript HIV Testing Practices

Introduction:
2007 HIV Diagnostics Conference
Bernard M. Branson, M.D.
Associate Director for Laboratory Diagnostics
Divisions of HIV/AIDS Prevention
National Center for HIVAIDS, Viral Hepatitis, STD, and TB Prevention
Centers for Disease Control and Prevention
The findings and conclusions in this presentation are those of
the author and do not necessarily represent the views of the
Centers for Disease Control and Prevention
HIV Viremia and Antibody Response
Peak viremia: 106-108 gEq/mL
HIV RNA (plasma)
Ramp-up viremia
DT = 21.5 hrs
HIV Antibody
HIV p24 Ag
p24 Ag EIA HIV MP-NAT -
1st gen
HIV ID-NAT -
“blip” viremia
0
11
10
Viral set-point:
102 -105 gEq/mL
2nd gen
3rd gen
16
20
22
30
Acute HIV Infection
40
50
60
70
80
90
100
1989: State of the Art
Western blot
EIA
Organization
Criteria
APHL/CDC
Any two: p24, gp41, gp120/160
ARC
Three or more bands, one from each
gene product group:gag, pol, env
CRSS
Two or more bands: p24 or p31 and
gp41 or gp120/160
Two env bands with or without gag or
pol
WHO
Indeterminate: Presence of any bands
Diagnostic Algorithm: 1989

The Public Health Service recommends that no
positive test results be given to clients/patients
until a screening test has been repeatedly
reactive (i.e., greater than or equal to two tests)
on the same specimen and a supplemental,
more specific test such as the Western blot has
been used to validate those results
1989 State of the Art
WHO HIV Diagnostic Testing: Strategy III
Asymptomatic; prevalence < 10%
A1
A1+
A1-
Negative
A2
A1+A2-
A1+A2+
Positive
A3
A1+A2-A3+
Positive
A1+A2-A3-
Indeterminate
SUDS: Single Use Diagnostic System for HIV-1
Blue color with reactive HIV test
Recommendation …and a Promise

Health-care providers should provide preliminary
positive test results before confirmatory results are
available in situations where tested persons benefit.

When additional rapid tests become available for
use in the United States, the PHS will re-evaluate
algorithms using specific combinations of two or
more rapid tests for screening and confirming HIV
infection.
1st and 2nd Generation EIA
Plasma/serum
(1 h/37o C)
IgG HIV antibody
Plasma/serum
Antigen coated well
1st - Viral lysate
2nd – Recombinant proteins
or synthetic peptides
Detects HIV
IgG if
present
enzyme
Enzymedetection
Color
reagent
anti-human IgG
3rd Generation “Sandwich” EIA
HIV antibody
Plasma/serum
IgG
Antigen coated well:
Recombinant proteins
or synthetic peptides
IgM
enzyme
Enzymedetection
HIV antigen
Detects HIV
IgM or IgG if
present
Color
reagent
4th Generation Combo EIA
HIV
antibody
Plasma/serum
Coated well:
HIV antigen
p24 antibody
Enzymedetection
p24 antigen
HIV antigen
p24
antibody
Detects HIV
antibody or
p24 antigen
if present
Color
reagent
…Or 2 Fluorescent labels allow independent
detection of antigen or antibody
Detection of HIV by Diagnostic Tests
Symptoms
p24 Antigen
HIV RNA
HIV EIA*
Western blot
0
1
After Fiebig et al, AIDS 2003;
17(13):1871-9
2
3
4
5
6 7
8
Weeks Since Infection
9
*3rd generation, IgM-sensitive EIA
*2nd generation EIA
*viral lysate EIA
10
EIAs Used by Public Health Labs
FDA approval date
% used by PHL
labs, 2004
Vironostika HIV-1 Microelisa
1987
63%
Abbott HIVAB HIV-1/2
1992
20%
Genetic Systems rLAV
1998
20%
Gen Sys HIV-1/HIV-2
2000
18%
Gen Sys HIV-1/2 Plus O
2003
10%
Vironostika HIV-1 Plus O
2003
2%
viral lysate EIA
EIAs Used by Public Health Labs
FDA approval date
% used by PHL
labs, 2004
Vironostika HIV-1 Microelisa
1987
63%
Abbott HIVAB HIV-1/2
1992
20%
Genetic Systems rLAV
1998
20%
Gen Sys HIV-1/HIV-2
2000
18%
Gen Sys HIV-1/2 Plus O
2003
10%
Siemens 1/O/2 eHIV
2006
viral lysate EIA
2nd generation EIA
3rd generation, IgM-sensitive EIA
Changes in Availability of EIAs
FDA approval date
% used by PHL
labs, 2004
Vironostika HIV-1 Microelisa
1987
63%
Abbott HIVAB HIV-1/2
1992
20%
Genetic Systems rLAV
1998
20%
Gen Sys HIV-1/HIV-2
2000
18%
Gen Sys HIV-1/2 Plus O
2003
10%
Bayer 1/O/2 eHIV
2006
viral lysate EIA
2nd generation EIA
3rd generation, IgM-sensitive EIA
Changes in Availability of EIAs
FDA approval date
% used by PHL
labs, 2004
Vironostika HIV-1 Microelisa
1987
63%
Abbott HIVAB HIV-1/2
1992
20%
Genetic Systems rLAV
1998
20%
Gen Sys HIV-1/HIV-2
2000
18%
Gen Sys HIV-1/2 Plus O
2003
10%
Siemens 1/O/2 eHIV
2006
viral lysate EIA
2nd generation EIA
3rd generation, IgM-sensitive EIA
2007 State of the Art
Uni-Gold Recombigen
Clearview Complete HIV 1/2
Multispot HIV-1/HIV-2
Reveal G3
Clearview HIV ½ Stat Pak
OraQuick Advance
Uni-Gold Recombigen
Clearview Complete HIV 1/2
Multispot HIV-1/HIV-2
Reveal G3
Clearview HIV ½ Stat Pak
OraQuick Advance
Reactive
Control
Recombinant HIV-1
Peptide HIV-2 Peptide HIV-1
Negative
HIV-1 & HIV-2
Positive
The ADVIA® Centaur™ Random Access
HIV 1/O/2 Enhanced (EHIV)
HIV 1/O/2 Enhanced (EHIV)

Multiple epitopes

3rd generation
“sandwich” format

Random access EIA

FDA-approved July 2006
On-board Refrigeration of 30 Different Assays
STAT sample requests without pausing
Results in ~60 minutes
APTIMA HIV-1 RNA Qualitative
Assay
Gen-Probe Incorporated
 Target capture specimen processing
 Transcription-Mediated Amplification (TMA)
 Dual Kinetic Assay
FDA approved September 2006
Qualitative RNA Assay: Intended Use

Aid to HIV-1 diagnosis

Diagnosis of acute HIV-1 infection in antibodynegative persons

Confirmation of HIV-1 infection in antibodypositive persons when it is reactive
Clinical Syndrome of Acute HIV

40-90% develop symptoms of Acute HIV

50%-90% with symptoms seek medical care

Of those diagnosed with Acute HIV, 50% of
patients seen at least 3 times before diagnosis
- Kahn et al, NEJM 1998
- Weintrob et al, Arch Int Med 2003
Pooled RNA Screening for Early HIV Infection
Pooled NAAT Screening for Early HIV Infection
A B C D E F G H I J
100
Individual
specimens
(HIV antibody negative)
10 Pools of 10
A B C D E F G H I J
1 Screening
Pool
Resolution Testing
A
Individual NAAT
testing on 10
specimens
10 pools of 10
tested with NAAT
Screening Pools
of 100 specimens
tested with NAAT
NC Pooled RNA Screening Program
109,250 clients Nov 02 – Oct 03
+
EIA/WB
NAAT
HIV antibody positive
583
-
-
25
+
F/U Testing
(Ab+NAAT)
+
(0.5%)
HIV Negative
108,632
(99.5%)
Acute HIV
23
(0.02%)
3-Test Algorithm: Antenatal Women
HIV-
Determine
n=1179
HIV+
Confirm w/Genie II
n=177 (15%)
n=999 (85%)
HIV-
HIV+
Capillus
n=8 (4.5%)
HIVHIV+
n=8 (100%)
Koblavi-Deme et al, J Clin Micro 2001
n=169 (95.5%)
n=0
3-Test Algorithm, Uganda
Rapid Test
Positive
Rapid Test
Negative
EIA/WB
Positive
EIA/WB
Negative
295
166
129
1220
4
1218
(Determine – Unigold – Stat Pak)
Sensitivity: 97.6% Specificity: 90.4%
- Gray et al, BMJ 2007
Current Assays with 15 Seroconverter Panels
cumulative proportion of positive tests
1.00
0.80
0.60
0.40
0.20
0.00
-40
-30
-20
-10
0
10
Days before/after positive Western blot
185 specimens from 15 seroconverters
- Owens et al, CDC unpublished data
20
25
20
15
10
5
OraQuick
WB positive
Uni-Gold
Vironostika HIV-1 (1st)
Multi-Spot
GS rLav (2nd)
Abbott HIVAB ½ (3rd)
Reveal G2
WB Indeterminate
Procleix RNA
BioRad HIV-1/2+O (3rd)
Current Assays with 15 Seroconverter Panels
0
Days before Western blot positive when 50% of Specimens Reactive
185 specimens from 15 seroconverters
- Owens et al, CDC unpublished data
Dilemmas

Screening in low prevalence

False-positive Western blots?

What metric?
Pediatric Diagnosis
Specificity, NPV, - LR of DNA PCR
New York State Department of Health
N=2,093 Children with definitive status
N=7,544 DNA PCR tests
1.5
Specificity
NPV
-LR
1
0.5
0
1
3
5
7
9
11
13 15 17 19
Last false negative= 7 weeks (43-49 days)
Specificity, NPV, - LR of DNA PCR
Perinatal AIDS Cohort Transmission Study
(PACTS) n=X tests
1.2
1
0.8
0.6
0.4
0.2
0
Specificity
NPV
-LR
0
2
4
6
8
10 12 14
16 18 20
Last False Negative = 11 weeks 11 (71-77 days)
Interpreting Test Results
Negative likelihood ratio:
likelihood of negative test when disease is present
likelihood of negative test when disease is absent
- Ratio of
false negative rate
specificity
{ true negative rate}
Interpreting Test Results
Negative likelihood ratio:
- Does not depend on prevalence
- Ratio < 0.1 = convincing diagnostic evidence
Ratio < 0.2 = strong diagnostic evidence
- Can be used with continuous variables (viral load)