Rapid HIV Assays June 6, 2012 Bay State Point of Care Collaborative - PowerPoint PPT Presentation

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 • 2 nd 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

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

Assays/Technologies available • 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 Storage Shelf Time for HIV-2? live to read OraQuick Oral fluid Waived Yes 2-27 C 12 20-40 WB Waived 2-8 C mo min Plasma Mod Uni- WB Waived No 2-27 C 12 10-12 Gold mo Serum/ Mod 2-8 C min plasma Reveal Serum/ Mod No 2-30 C 12 Imm. G3 plasma 2-8 C mo

Performance of rapid HIV assays • 6 FDA-approved rapid HIV assays Test Specimen CLIA Approved Storage Shelf Time for HIV-2? live to read Multispot Serum/ Mod Yes* 2-8 C 12 Up to 24 hr plasma or or 20-30 C 3 mo Clearview WB Waived Yes 8-30 C 24 15-20 Stat-Pak mo Serum/ Mod min plasma Clearview WB Waived Yes 8-30 C 24 15-20 Complete Serum/ Mod mo min plasma

Performance of rapid HIV assays Sensitivity Specificity (95% C.I.) (95% C.I.) OraQuick Advance 99.3%(98.4-99.7) 99.8%(99.6-99.9) - oral fluid 99.6%(98.5-99.9) 100%(99.7-100) - whole blood 99.6%(98.9-99.8) - plasma 99.9%(99.6-99.9) Uni-Gold Recombigen - whole blood 100%(99.5-100) 99.7%(99.0-100) - serum/plasma 100%(99.5-100) 99.8%(99.3-100)

Performance of rapid HIV assays Sensitivity Specificity (95% C.I.) (95% C.I.) Reveal G3 99.8%(99.2-100) 99.1%(98.8-99.4) - serum Multispot 100%(99.94-100) 99.93%(99.79-100) - serum

Performance of rapid HIV assays Sensitivity Specificity (95% C.I.) (95% C.I.) Clearview Stat-Pak 99.7%(98.9-100) 99.9%(99.6-100) - whole blood 99.7%(98.9-100) 99.9%(99.6-100) - serum/plasma Clearview Complete 99.7%(98.9-100) 99.9%(99.6-100) - whole blood 99.7%(98.9-100) 99.9%(99.6-100) - serum/plasma

Performance of rapid HIV assays • 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

Performance of rapid HIV assays • 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 4 th 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

Impact of new CLSI guidelines for HIV testing • 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

Impact of new CLSI guidelines for HIV testing • 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

Rapid HIV testing US Public Health • 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

Rapid HIV testing US Public Health • 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

Rapid HIV testing US Public Health • 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)