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Objectives

Comparative Performance of Dual 3rd Generation Immunoassays as a Potential Laboratory-Based HIV-1/2 Testing Strategy. B. Bennett, S. Fordan, O. David, M. Salfinger, M. Chan, D. Willis, S. Crowe, Florida Department of Health, Bureau of Laboratories-Jacksonville, FL., USA. Objectives. Primary:

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Objectives

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  1. Comparative Performance of Dual 3rd Generation Immunoassays as a Potential Laboratory-Based HIV-1/2 Testing Strategy.B. Bennett, S. Fordan, O. David, M. Salfinger, M. Chan, D. Willis, S. Crowe, Florida Department of Health, Bureau of Laboratories-Jacksonville, FL., USA.

  2. Objectives Primary: • To assess clinical performance of each immunoassay for possible ITN purposes within our current algorithm, not specifically for a dual immunoassay algorithm design. Strategy-specific: • Increase algorithm sensitivity w/o compromising specificity as compared to a traditional algorithm. • Demonstrate potential reagent cost-effectiveness on seropositive results as compared to a traditional algorithm. • Demonstrate improve testing TAT on non-seronegative reporting. • Reduce the number of inconclusive reports.

  3. Methods • Assay selection;BioRad’s HIV-1/2 Plus O EIA Siemens Advia Enhanced HIV-1/O/2 • n = 2,765 fresh serum samples tested by both 3rd generation immunoassays. • TP = 92 (3.3%), 90 WBlot +, 1 NAAT +, 1 subsequent seroconversion • TN = 2,673

  4. Strategy 3. HIV 1/2 Dual Immunoassay A1 = HIV1/2 immunoassay(e.g. EIA or CIA) n = 2765 TP = 92 (3.3%) A1 (+) BR1/2/O = 98E1/2/O = 98 A1 (-) Negative for HIV-1 & HIV-2 antibodies BR1/2/O = 2667E1/2/O = 2667 A1 (- -) Repeat A1**This study did not include the (duplicate) ? ? repeat AI pathway. A2 = HIV 1/2 immunoassay in duplicate (e.g. EIA or CIA or non-waived rapid) A2(- -) E1/2/O = 2BR1/2/O = 2 A1 (++ or +-) A2 (++) (+-) Presumptive positive for HIV-1 or HIV-2 antibodies; requires medical follow-up for further evaluation and testingE1/2/O = 96 BR1/2/0 = 96A1/A2 sensitivity = 100% PPV = 95.8% A1/A2 specificity = 99.85% NPV = 100% Inconclusive for HIV antibodies; request plasma redrawfor NAAT *. Requires medical follow-up for further evaluation and testing. HIV-2 testing; Strategy 5, if 1 or more of the following apply: 1) Indicated by clinical presentation 2) Indicated by local HIV-2 prevalence 3) Indicated by client/patient travel or risk history *If window period infection is suspected, refer to Acute HIV Infection Testing, Strategy 4.

  5. Table 1Individual Assay & Strategy PerformanceAssay(s) Clinical Sensitivity Clinical Specificity * Optional replacement with Advia HIV-1/O/2 w/ same performance.** Based on Western Blot negative and/or limited seronegative follow up.

  6. Table 2 Discordant Results Specimen HIV-1/2 Plus O Advia HIV-1/O/2 Western NAAT Follow up S/CO* Index* Blot (HIV-1) (Aptima HIV-1 RNA) * <1.0 s/co or index values are exact, >1.0 s/co or index values are averages of replicates. Color representations; false positive screens, false negative blots,confirmed HIV-1 acute infections.

  7. Conclusions • Increased sensitivity over the reference method. • Increased specificity over either 3rd generation immunoassay in stand-alone use. • Comparable specificity to a licensed HIV-1 WBlot, the licensed HIV-1 NAAT assay and several POC HIV-1/2 rapid devices. • Did not demonstrate the ability to detect a very limited number of confirmed HIV-1 acute infections. • Laboratory-TAT of seropositive results potentially could be reduced by 1-3 days. • Diagnostic reagent costs could be reduced for non-negative specimens by 26-43%.

  8. Table 3Application ComparisonsStrategy Turn-Around-Time (non-negatives) Reagent Costs

  9. Study Notes & Needs • Need to expand study size & include more acute and early infections(focus on increasing specificity w/o compromising the improved sensitivity); - Better assay(s) selections? - The addition of a 3rd assay? - The use of a S/CO threshold value to assist in further testing, referrals and/or reporting needs? • Need for reproducibility data over more than one lot# per assay. • Need for seroconversion panels(budgetary restraints in our case) • Note: Based on this study’s limited number of AIs (4) and if AIT is desired, perhaps consider the Strategy 5 add-on. • Note: Large automated analysis platforms are often required to accompany these newer diagnostic assays and possibly could impact the cost-effectiveness of a dual immunoassay algorithm. Use of other diagnostic applications (HBV, HCV, etc.) on the secondary platform may counter some of the additional costs. • Note: The “Random access” feature of at least one immunoassay has the potential to decrease TAT in a dual immunoassay algorithm but the “control bracketing” requirement may lessen the appeal when testing small numbers of initial reactives.

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