routine hiv screening in health care settings

Routine HIV Screening in Health Care Settings

David Spach, MD

Clinical Director

Northwest AIDS Education and Training Center

Professor of Medicine, Division of Infectious Diseases

University of Washington Seattle

This project was funded under cooperative agreement number U65/PS000821 from the Centers for Disease Control and Prevention (CDC).

HIV Diagnostic Testing


• Types of HIV Diagnostic Tests

• Initial and Supplemental HIV Tests

• Sensitivity and Specificity of HIV Tests

• Laboratory-Based HIV Testing Algorithms

• Point-of-Contact (Rapid) HIV Testing Algorithms

• Diagnosis of Acute HIV

Types of HIV Diagnostic Tests

HIV Antibodies HIV-1 RNA HIV p24 Antigen

Most Common Test for

Established Infection

Rarely Used

Future use: 4th

Generation EIA

Used for Acute HIV and Indeterminate WB

Initial and Supplemental HIV Tests

• Initial Test

- Enzyme Immunoassay (EIA)

- Chemiluminescent Immunoassay (CIA)

• Supplemental Tests

- Western blot

- Indirect Immunofluorescence Assay (IFA)

- Qualitative HIV-1 RNA

Generation of EIA Tests

First Second Third *Fourth

Uses crude viral lysate Detects IgM and IgG in

“Sandwich” EIA

Uses recombinant HIV antigens or peptides Detects HIV antibodies and p24 antigen

*Not US FDA-approved as of 10/1/09

Traditional HIV EIAs

• Based on color change/fluorescence

• Change compared with standardized cut-off

• Result positive or negative

• No specific antibody reaction information

• Multiple samples run with traditional EIA

96-Well Microtiter Plate EIA Interpretation of EIAs

HIV-1 Western Blot Antigens

p = protein

gp = glycoprotein

Number = molecular weight

Components Used in HIV-1 Western Blot

Human HIV Antibodies

(from patient serum)

Y YY Y

HIV Western blot Strip

Y Y

HIV Antigens

(on Western blot)

YY Y Antihuman IgG Antibodies

Enzyme Detector

Color Reagent

Sample HIV-1 Western Blot

Y Y

Y

Y Y

Y

Y

YY Y

Y

Y

Antibodies to gp120

Anti-human IgG

Enzyme Detector

HIV gp120 antigen

Color Reagent

Antibodies to p24

Enzyme Detector

HIV p24 antigen

Color Reagent

Anti-human IgG

Test Completed gp120 & p24 bands Visible

HIV-1 Gene Products & Western Blot

HIV-1 and HIV-2 Gene Products & Western Blot

Interpretive Criteria for HIV-1 Western Blot

Source: CDC. MMWR. 1989:38(S-7):1-7.

Positive Control


Source: CDC. MMWR. 1989:38(S-7):1-7.

Negative

No bands:


Source: CDC. MMWR. 1989:38(S-7):1-7.

Positive

At least two of the following bands:

p24

gp41

gp120/160


Source: CDC. MMWR. 1989:38(S-7):1-7.

Indeterminate

One or more bands present

Not meeting positive criteria

Examples

Most common bands seen with

indeterminate Western blot (IWB)

p17, p24, p55

Sensitivity

Probability that test is positive if person is infected

HIV Antibody Test: Sensitivity

HIV Antibody Test: SensitivityPersons Infected with HIV: n = 50

Example

HIV Antibody Test: SensitivityHIV Antibody Testing: 49/50 PositivePersons Infected with HIV: n = 50

Example

HIV Antibody Test: SensitivityHIV Antibody Testing: 49/50 PositivePersons Infected with HIV: n = 50

Sensitivity = 49/50 = 98%

Example

Sensitivity of HIV Antibody Tests Used in US

HIV Antibody Tests

Sensitivity >> 99%

HIV Antibody Test: False Negative

HIV Antibody TestingHIV-Infected Persons

Example

HIV Antibody Test: False Negative

HIV Antibody TestingHIV-Infected Persons

False Negative

Example

Some Causes of False-Negative Antibody Tests

• Acute HIV Infection

• Advanced HIV Infection

• Antiretroviral Therapy

Specificity

Probability that test is negative if person is not infected

HIV Antibody Test: Specificity

HIV Antibody Test: SpecificityPersons NOT Infected with HIV: n = 50

Example

HIV Antibody Test: SpecificityHIV Antibody Testing: 48/50 NegativePersons NOT Infected with HIV: n = 50

Example

HIV Antibody Test: SpecificityHIV Antibody Testing: 48/50 NegativePersons NOT Infected with HIV: n = 50

Specificity = 48/50 = 96%

Example

HIV Antibody Test: False Positive

HIV Antibody TestingPersons NOT Infected with HIV

Example

HIV Antibody Test: False Positive

HIV Antibody TestingPersons NOT Infected with HIV

False Positive

Example

Specificity of HIV Antibody Tests Used in US

Initial HIV Antibody Tests

Specificity > 98%

Supplemental HIV Test

(if initial test positive)

Specificity >> 99%

HIV Antibody Test: Specificity

True Infection

False Positive

False Positives: proportion of false-positive tests increases

in populations with low HIV prevalence

Causes of False-Positive HIV Antibody Tests

• Other Viral Diseases

• Hematologic Disorders

• Liver Disease

• Immunizations

• Autoimmune Disorders

Interpreting Test Results

Sensitivity: Probability test = positive IF person = positive

Specificity: Probability test = negative IF person = negative

Positive Predictive Value: Probability person = positive IF test = positive

Negative Predictive Value: Probability person = negative IF test = negative

Positive Predictive Value of HIV Tests in Populations with Differing HIV Prevalence

HIV Prevalence True Positive (#) False Positive (#) Positive Predictive Value

10% 100 2 98%

5% 50 2 96%

2% 20 2 91%

1% 10 2 83%

0.5% 5 2 71%

0.2% 2 2 50%

0.1% 1 2 33%

Example: HIV Testing 1,000 Persons

General Approach to HIV Diagnostic Testing

SupplementalInitial

Optimized for

Sensitivity

Optimized for

Specificity

1989 CDC/ASTPHLD HIV Testing Algorithm

Initial Supplemental

EIA

Western blot

or

IFA

Repeatedly Reactive

Source: CDC. MMWR. 1989;38(S-7):1-7.

Modern HIV Testing Algorithms

Source: CDC. MMWR. 2001;50(RR19):1-58.

Initial

Laboratory-Based Approach to HIV

Testing

Point-of-Contact

Approach to HIV Testing

Diagnosing Acute HIV

HIV Testing Algorithms

http://www.aphl.org/aphlprograms/infectious/hiv/Pages/HIVStatusReport.aspx

Laboratory-Based HIV Testing Algorithms

Initial

HIV Negative

Nonreactive

HIV-1/HIV-2

Immunoassay*

*Enzyme Immunoassay (EIA)

or

Chemiluminescent Immunoassay (CIA)


Initial

Reactive

Repeat Testing

(in duplicate)

HIV-1/HIV-2

Immunoassay*


or



Initial

Reactive

Repeat Testing

(in duplicate)

HIV Negative

Both Nonreactive

HIV-1/HIV-2

Immunoassay*


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*

HIV Negative

Negative


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*

HIV Negative

Negative

Test for HIV-2 with any of Following:

• Indicated by local HIV-2 prevalence

• Indicated by travel or risk history

• Indicated by clinical presentation


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*

Positive

HIV Infected*Enzyme Immunoassay (EIA)

or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1/HIV-2

Immunoassay*

Indeterminate

HIV-1 Western blot


or


Approach to Indeterminate Western blot

HIV-1 Western blot

Indeterminate


HIV-1 Western blot

Repeat HIV-1 Western blot after 2-4 Weeks

HIV RNA Test

or

Indeterminate

Modern Approach to Indeterminate Western blot

Source: CDC. MMWR. 2001;50(RR19):1-58.

Indeterminate

(no recent exposure)

HIV-1 Western blot

HIV Infected Not HIV Infected


HIV RNA Test

or -+

Indeterminate


HIV Infected

-+

HIV-1 Western blot


HIV RNA Test

or

Indeterminate

Not HIV InfectedIndeterminate



Not HIV InfectedHIV Infected

-+

HIV-1 Western blot


HIV RNA Test

or

Indeterminate

Indeterminate

(RECENT EXPOSURE )

Further Evaluation Needed


HIV-1 Western blot

HIV Infected Not HIV Infected


HIV RNA Test

or -+

Indeterminate

Indeterminate


Point of Contact (Rapid) TestsUni-Gold Recombigen Multispot HIV-1/HIV-2 Clearview Complete HIV 1/2

Oraquick Advance HIV-1/2Reveal G3 Clearview HIV 1/2 Stat Pak

Point of Contact (Rapid) HIV TestsFDA-Approved Tests in US, August 2009

Point of Contact (Rapid) HIV Test FDA Approval Manufacturer

OraQuick ADVANCE Rapid HIV-1/2 Antibody Test 2002 OraSure Technologies

Uni-Gold Recombigen HIV 2003 Trinity Biotech

Reveal G-3 Rapid HIV-1 Antibody Test 2003 MedMira, Inc.

Multispot HIV-1/HIV-2 Rapid Test 2004 BioRad Laboratories

Clearview HIV 1/2 STAT-PAK 2006 Inverness Medical

Clearview COMPLETE HIV 1/2 2006 Inverness Medical

Point of Contact (Rapid) HIV Testing Algorithms

Nonreactive

Rapid Test

Source: CDC. MMWR. 2004;53(10):221-2.


Source: CDC. MMWR. 2004;53(10):221-2.

HIV Negative

Nonreactive

Rapid Test

Client considered HIV-negative unless recent exposure to HIV has occurred


Source: CDC. MMWR. 2004;53(10):221-2.

Rapid Test

Reactive

Preliminary Positive

Counsel Client that HIV has not been Confirmed

Follow-Up Supplemental Testing is Necessary


Rapid Test

Reactive


Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

Source: CDC. MMWR. 2004;53(10):221-2.


Source: CDC. MMWR. 2004;53(10):221-2.

Rapid Test

Reactive


Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

EIA

CIA

Optional

EIA or CIA testing optional

Perform supplemental testing regardless of EIA or CIA result

EIA = Enzyme Immunoassay

CIA= Chemiluminescent Immunoassay


Initial Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

Positive

HIV Infected

Rapid Test

Reactive


EIA

CIA

Optional

Source: CDC. MMWR. 2004;53(10):221-2.


Source: CDC. MMWR. 2004;53(10):221-2.

Rapid Test

Reactive


Follow-up repeat supplemental testing 4 weeks after original reactive Rapid Test

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

Non-Reactive

Indeterminate

or


Source: CDC. MMWR. 2004;53(10):221-2.

Rapid Test

Reactive


Repeat Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

Follow-up repeat supplemental testing 4 weeks after original reactive Rapid Test

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

Non-Reactive

Indeterminate

or

4 weeks


Initial

Reactive

HIV-1/HIV-2

Immunoassay*

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA


Initial

Reactive

Repeat Testing

(in duplicate)

HIV Negative

Both Nonreactive

HIV-1/HIV-2

Immunoassay*


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*


or



Initial

Reactive

Repeat Testing

(in duplicate)

Repeatedly Reactive

Supplemental

HIV-1 Western blot

or

HIV-1 IFA

or

HIV-1 RNA

HIV-1/HIV-2

Immunoassay*

HIV Negative

Negative


or



HIV RNA levels abruptly rise within several weeks after acute infection

Infection

HIV RNA


HIV RNA “spike” precedes production of detectable HIV antibodies

Infection

HIV RNA Antibody Titer

Detectable Antibody

Diagnosing Acute HIV: Eclipse Period

Eclipse Period = Time between infection and detectable HIV RNA

Infection

HIV RNA

Diagnosing Acute HIV: Window Period

Window Period = Time between infection and detectable HIV antibodies

Infection

Antibody Titer

Detectable Antibody

Window Period

Modified from: Branson BM. Clin Infect Dis. 2007;5:S221-5.

Timing of Diagnostic Tests after Initial HIV Infection

HIV RNA Detectable

HIV EIA*

Western blot

HIV EIA*HIV EIA*

3rd

Generation, IgM-Sensitive EIA

2nd

Generation EIA

Viral Lysate EIA

Weeks after HIV Infection


Modified and Reproduced with permission from American Society of Microbiology

Source: Owen SM, et al. J Clin Microbiol. 2008;46:1588-95.



Rapid HIV

HIV-1 RNA


Diagnosing Acute HIV: Acute HIV

Acute HIV = patients may present with acute retroviral syndrome/illness

Acute HIV

Infection

Antibody Titer

Detectable Antibody

HIV RNA

Source: Vanhems P, et al. AIDS. 2000;14:375-81.

Signs and Symptoms of 160 Patients with Acute HIV

Diagnosing Acute HIV: Clinical Manifestations

Laboratory Diagnosis of Acute HIV

Acute HIV

Infection

Antibody Titer

Detectable Antibody

HIV RNA

• Positive HIV-1 RNA Assay

• Negative HIV Antibody Test

Acknowledgement

The project was funded under cooperative agreement

number U65/PS000821 from the Centers for Disease

Control and Prevention (CDC).

routine hiv screening in health care settings

Documents

sample hiv

recombinant hiv antigens

traditional hiv eias

rna hiv p24 antigen

western blotsource

rna1generation of eia

western blot antigens

gene products western