Rapid HIV Assays - Whitehat Com

Rapid HIV Assays

June 6, 2012 Bay State Point of Care Collaborative

Brad S. Karon, MD, PhD Associate Professor of Laboratory Medicine and

Pathology Mayo Clinic

Rochester, MN

Outline

• HIV in US and other countries • Performance of rapid HIV assays • Need for rapid HIV in public health • Need for rapid HIV in hospitals • Conclusions

HIV in US

• ~ 1,000,000 HIV infected in US • ~ 250,000 unaware of HIV status • Net HIV diagnosis and AIDS decreased

thru 1990s • Increased awareness and testing • Better treatment

• Rate of decline has leveled off • Limitations in access to testing, counseling

and treatment

HIV in US

• Screening for HIV antibodies done with EIA test, takes 3-4 hours technical time, confirmation if positive

8-24 hours TAT standard in most labs

• CDC now recommends HIV screening for all

adults and adolescents ages 13-64 in healthcare setting

• How to get testing, counseling done in order to initiate treatment

• Rapid HIV tests

HIV outside US

• ~ 30 million adults and ~ 3 million children living with HIV worldwide in 2011

• ~ 2.7 million new infections and ~ 2 million deaths from AIDS-related causes in 2010

• Around half become infected before age 25 • 2nd leading cause of death among 20-24 yo

• Sub-Saharan Africa accounts for 2/3 HIV • Over half living with HIV are women • Antiviral treatment increasingly effective • Major effort to prevent transmission to

children

HIV outside US

• Multiple challenges in identifying HIV infected

• Resources for screening • Test and sample stability • Resources for confirmation of pos screens • Lab personnel for testing

• Rapid HIV • Fingerstick or oral fluid sample types • Simple methods require minimal training • No lab equipment, low cost • Long shelf-life and RT storage

Assays/Technologies available • Immunochromatographic (lateral flow)

immunoassay HIV Ag applied to line on nitrocellulose strip Blood diluted in buffer, added to well Lateral flow pulls blood past indicator and over

to test line (Ag), then to control line (indicator)

Assays/Technologies available

• Immunochromatographic (lateral flow) immunoassay

• Advantages: Fast (10-20 minutes), few steps, minimal sample

processing, varied sample types (whole blood, serum, plasma, oral fluid), many CLIA waived

• Disadvantages: Cannot distinguish HIV-1 and HIV-2, need to

dilute sample in buffer, interpretation of lines


• Immunoconcentration (dot blot) Ag immobilized on porous membrane Diluted sample applied to membrane Buffer/wash steps, then developer applied Dot develops if positive


• Immunoconcentration (dot blot)

• Advantages: Fast (5-15 minutes) Can distinguish HIV-1 and HIV-2 In theory greater specificity

• Disadvantages Multiple timed steps, usually requires serum or

plasma, moderate complexity

Performance of rapid HIV assays • 6 FDA-approved rapid HIV assays

Test Specimen CLIA Approved for HIV-2?

Storage Shelf live

Time to read

OraQuick Oral fluid WB Plasma

Waived Waived Mod

Yes 2-27 C 2-8 C

12 mo

20-40 min

Uni-Gold

WB Serum/ plasma

Waived Mod

No 2-27 C 2-8 C

12 mo

10-12 min

Reveal G3

Serum/ plasma

Mod No 2-30 C 2-8 C

12 mo

Imm.

Performance of rapid HIV assays • 6 FDA-approved rapid HIV assays

Test Specimen CLIA Approved for HIV-2?

Storage Shelf live

Time to read

Multispot Serum/ plasma

Mod Yes* 2-8 C or 20-30 C

12 or 3 mo

Up to 24 hr

Clearview Stat-Pak

WB Serum/ plasma

Waived Mod

Yes 8-30 C

24 mo

15-20 min

Clearview Complete

WB Serum/ plasma

Waived Mod

Yes 8-30 C

24 mo

15-20 min

Performance of rapid HIV assays

Sensitivity (95% C.I.)

Specificity (95% C.I.)

OraQuick Advance - oral fluid - whole blood - plasma

99.3%(98.4-99.7) 99.6%(98.5-99.9)

99.6%(98.9-99.8)

99.8%(99.6-99.9)

100%(99.7-100)

99.9%(99.6-99.9)

Uni-Gold Recombigen - whole blood - serum/plasma

100%(99.5-100)

100%(99.5-100)

99.7%(99.0-100)

99.8%(99.3-100)




Reveal G3 - serum

99.8%(99.2-100)

99.1%(98.8-99.4)

Multispot - serum

100%(99.94-100)

99.93%(99.79-100)




Clearview Stat-Pak - whole blood - serum/plasma

99.7%(98.9-100) 99.7%(98.9-100)

99.9%(99.6-100)

99.9%(99.6-100)

Clearview Complete - whole blood - serum/plasma

99.7%(98.9-100) 99.7%(98.9-100)

99.9%(99.6-100)

99.9%(99.6-100)


• Rapid HIV Ab tests use only one (gp41) or two (gp120 and gp41) antigens as targets

• Despite smaller number Ag targets sensitivity compares well to lab EIA

• One limitation patients treated with high dose antiviral agents (anti gp 41 decreased with therapy)

• Treated patients unlikely to be tested with rapid HIV test


• Some studies found poorer detection of HIV Ab early in infection with rapid tests

• Ab EIA longer window period than Ag/Ab or NAT

test • Fewer antigen targets in rapid tests may lead to

fewer early pos results compared to lab EIA • Some data suggests variability among rapid tests

(some may detect IGM Ab better)

Performance of rapid HIV assays • Oral fluid testing • NYC public screening program 2005-08 • Higher rate of false pos Oraquick results with oral

fluid compared to WB • Many false pos seen in one site, no cause

determined • Still within stated 98% specificity • CDC now warns that oral fluid testing less

sensitive and specific than WB or serum/plasma

Impact of new CLSI guidelines for HIV testing

• CLSI M-53A June 2011 • Six testing algorithms developed to cover various

situations • CDC endorsement expected soon

• Algorithm one • Initial screen 4th gen HIV 1/2 Ab/Ag EIA (repeat in

duplicate if pos) • Next step HIV differentiation assay

• Multispot only FDA-approved differentiation assay (lab or POC), many labs may bring in Multispot

• Confirm with NAT, WB, or IFA, etc


• Algorithm two (old way) • Screen with HIV 1/ 2 Ab EIA (repeat in duplicate if

pos) • Confirm with NAT, WB, IFA, etc • Compared to algorithm one has longer window

period

• Algorithm 3 (presumptive 2 EIA) • Screen with HIV1/2 Ab EIA • Confirm with different HIV 1/2 Ab EIA • Repeat pos EIA assay-dep • Used frequently in low resource settings


• Potential for false pos results with 2 rapid HIV algorithm

• Baveewo et al., BMC Research Notes 2012;5:154 • 3388 Ugandans tested by serial rapid HIV tests (3)

• 1275 tested positive on first rapid HIV assay • 984 positive on second rapid HIV assay • 261 neg on second rapid HIV assay

• 29 positive on third rapid HIV assay • 14/29 negative by DNA qual PCR

• Potential for false pos results when only rapid HIV assays used to determine HIV status

Rapid HIV testing US Public Health

• Rapid HIV tests FDA-approved for “for use by agents of a clinical laboratory”

• Waived tests applied in US public health efforts • Community-based organizations, state-sponsored

screening programs, ED, STD clinics

• 2004 study found increased functional error rate when OraQuick used by non-laboratorians (incomplete loop filling most common)

• Transcription errors, other clerical errors also observed


• Overall, sens and spec of waived rapid HIV tests very good in public health setting

• Exception oral fluid testing in one NYS site

• Variable effectiveness of screening programs • Rapid screening effective in getting HIV results to

population that otherwise would not be screened • Rates of counseling and confirmation testing vary • Rates of entry into medical treatment vary from 47-

97% • Publicly sponsored programs do better than

privately sponsored


• CDC Expanded Testing program • Funded public health program to expand HIV

screening in high HIV burden areas and for populations without access to testing

• Program funded in 25 states with at least 140 AIDS cases diagosed in African-Americans in 2005

• From 2007-2010 over 2.5 million HIV tests performed, 67% in healthcare settings

• 29,503 (1.1%) HIV pos of which 18,432 (0.8%) new diagnosis

• Of new HIV diagnosis, 74.3% linked to HIV care


• Expanded HIV testing in African-Americans

• As of 2008, CDC estimates that of 1.2 million Americans with HIV, 500,000 African-American

• In 2009 African-Americans accounted for 52% of HIV diagnosis

• HIV prevalence rate for African-American women 18-fold higher than white women

• HIV prevalence rate for African-American men 6-fold higher than white men

Rapid HIV testing US Public Health • Expanded HIV testing in African-Americans

• Estimated 21% of infected African-Americans do

not know their HIV status

• Of over 2.5 million tested 2007-10, 60% were African-American

• Rate of new HIV diagnosis among African-Americans 0.8% (same as overall)


• High risk behaviors reported among newly diagnosed African-Americans

• Males • Sexual contact with other males 36% • High risk heterosexual contact 35% • Low risk heterosexual contact 16% • Intravenous drug use 5%

• Females • High risk heterosexual contact 62% • Low risk heterosexual contact 21% • Intravenous drug use 6%

• Behaviors not sig different from white populations • African-Americans with high risk behaviors tested less

Rapid HIV testing hospitals

• High risk mothers in labor and delivery units

• Outpatient clinics or ED, especially those serving poor, transient or homeless

• Index patient when healthcare worker exposed to blood/body fluids from high risk (serostatus unknown) patient


• High risk OB CDC (2000): 6000-7000 HIV-infected women delivered

babies 280-370 HIV-infected babies born, 40% born to

mothers not diagnosed before delivery Risk perinatal transmission 25% when neither anti-

retroviral therapy or obstetric intervention Risk perinatal transmission 2% when both anti-

retroviral therapy and obstetric intervention HIV screening recommended part of prenatal care for

all women


• CDC now recommends all women not previously tested for HIV receive rapid HIV test when presenting in labor

• No longer just hospitals doing high risk OB that must offer rapid HIV to meet CDC and other guidelines


• Outpatient clinics/ED • Among those tested at CDC-sponsored public

health clinics, apprx. 30% of patients do not return for HIV results

• CDC now recommends HIV screening for all adults and adolescents ages 13-64 in healthcare setting

• What good is screening if patients do not receive counseling or results?

• Major push for ED-based screening to meet CDC goals in some urban areas


• Challenges for ED-based population testing

• Targeting high risk populations • Delivering effective test counseling and

setting up referrals in ED setting • Ensuring follow-up of presumptive positive

results and entry into healthcare system


• Index patient testing Risk of HIV transmission ∼ 0.3% percutaneous

exposure, ∼ 0.09% body fluid CDC recommendations: Evaluate index patient for HIV status and risk ASAP PEP should be started ASAP if index patient positive If index patient serostatus unknown, evaluate type of

exposure and risk factors, offer PEP for high risk index Consider rapid HIV if EIA not available in 24-48 hrs Rapid HIV, even compared to 24 hr TAT, may eliminate

need for 1-2 doses PEP Consider rapid HIV for high risk, serostatus unknown


• Index patient testing CDC guidelines suggest rapid HIV may be useful

if EIA cannot be obtained in 24-48 h Many hospitals use rapid HIV test for high risk index patient May reduce need for prophylaxis May increase exposure reporting May reduce cost of exposures Some hospitals now do rapid HIV for all exposures

• Rapid HIV testing of employee not useful

Mayo Clinic Evaluation

• Study Design Oraquick, Uni-Gold and Multi-spot evaluated 50 blood bank samples (HIV negative) 20 HIV positive samples (viral load positive) 20 cross-reactive samples (Hep A or B, EBV) 10 EIA positive, WB negative samples Background clarity and line intensity graded 0-3 (0 background best, 3 line intensity best)


• HIV negative samples Oraquick: 50/50 negative Uni-Gold: 49/50 negative (1 false positive) Multi-spot: 48/50 negative (2 false positives,

undifferentiated) Background clarity: At 10 min, all had 0 background except one sample on

Uni-Gold (hemolyzed) At 20 min, Uni-Gold and Multi-spot had higher

background than Oraquick


• Positive samples • All 3 methods had 20/20 positive • All samples resulted in 2-3+ line intensity • All 3 methods have excellent sensitivity


• Crossreactive samples • 1 sample positive by all 3 methods, record

reviewed and re-classified as HIV positive based on history HIV infection

• 19/19 crossreactive samples negative by all 3 methods


• EIA Positive, WB negative samples • 10/10 negative by both Oraquick and Uni-

Gold methods • 6/6 negative by Multi-spot (insufficient

volume 4 samples)


OraQuick

% (95% CI) *

Uni - Gold

% (95% CI) Multispot

% (95% CI)

Specificity 100 (95 - 100) 98.7 (93 - 100) 97.3 (91 - 100)

Sensitivity 100 (84 - 100) 100 (84 - 100) 100 (84 - 100)

P ositive Predictive Value 100 (84 - 100) 95. 5 (77 - 100) 91.3 (72 - 99)

Negative Predictive Value 100 (95 - 100) 100 (95 - 100) 100 (95 - 100)

Mayo Implementation

• Ordered by employee health on high-risk, serostatus unknown index patients

• Performed in Stat lab • Positive and negative QC for every patient sample

run, each new lot or shipment • All positives reflex WB • All negatives 1st year were run by EIA No false negatives, discontinued • Quarterly crosschecks with positive samples • External PT at least semi-annually

• Two years after implementing, started rapid HIV on all exposures

Conclusions • HIV still public health threat in US

• 25% infected are still undiagnosed

• Rapid HIV tests have excellent sensitivity for the detection of HIV antibodies

• Specificity problems may be function of users/technique

• Special consideration for oral fluid testing?

• Rapid HIV testing may be useful for hospital obstetrics, clinic/ED settings, or as part of employee exposure protocol

• With proper training/competency/oversight, rapid HIV testing can be very beneficial in healthcare settings

Questions?

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