Presentation on theme: "Comparison of the HIV LIA vs WB on HIV-Negative Samples CDC-HIV Diagnostics Meeting “New Diagnostic Technologies” Dec 5-7, 2007 Dr. John Kim National Laboratory."— Presentation transcript:
Comparison of the HIV LIA vs WB on HIV-Negative Samples CDC-HIV Diagnostics Meeting “New Diagnostic Technologies” Dec 5-7, 2007 Dr. John Kim National Laboratory for HIV Reference Services Public Health Agency of Canada Ottawa, Ontario
Figure 1. HIV Testing (general) sample screening confirmatory EIA non-reactiveREPORT Repeat reactive Final Diagnosis (a) Western blot (HIV-1) (b) RIPA (HIV-1, HIV-2) (C) LIA (HIV-1/HIV-2) (d) PCR –Roche, Hpol, gp41, HIV-2 RNA – bDNA, Roche, Abbott, HIV-2 Q
INNO-LIA HIV (new technology ?) New anti-human immunodeficiency virus immunoblot assays resolve non-specific Western blot results. (Zaaijer et al, Transfusion, 37:193, 1997). Validation of a new immunoblot assay for confirmation of human immunodeficiency virus infection (Zaaijer et al, Transfusion, 38:776, 1998). Ability of the Innogenetics Inno-Lia to distinguish HIV-1, HIV- 2 and dually reactive sera. (Granade et al, Abstr. Gen Meet Am Soc Microbiol, 92:416 [T-47[, 1992. Confirmation of HIV infection with the line immune assay (INNO-LIA) using whole blood impregnated filter paper discs. (Kestens et al, Abstr. Int Conf Aids 5:309 [TBP 135], 1989.
gp160 gp120 p24 p31 p17 gp41 HIV-2 HIV-1 “O” ? A D C E F F 2 2 “O” ? A D C E F F + Detection of non-Subtype B HIV reference samples on Subtype B HIV-1 (WB & LIA) antigen kits
HIV WB Quality ISSUES-Canada SiteLot #DateProblems Sask 927304 Sep 04 Negative control had a few faint bands, slightly above where you would expect the gp160 and slightly below p18 Alberta 931422 Apr 05 Weak positive control strips of Biorad Western Blot kit that the 120 band is not visible after the maximum incubation time Halifax 928718 & 928634 Mar- Apr 05 NFLD 929713 May 05 Quebec 935405 Jan 06 Faint band at p18 on the negative control
Methods BIO-RAD Wb vs INNOGenetics HIV 1/2 Score > 1000 samples, (2002-2007) n=823 (77-pos; 746-neg), final status known/WB- LIA results Neg samples (746) n=472, LIA-neg/Wb-neg n=232*, LIA-neg/Wb-ind n=42, LIA-ind/Wb-ind ,LIA-ind/Wb-neg , LIA-pos/Wb-pos/neg/ind 
Living with the Wb-Improvements Wb still most widely used (licensed) confirm tool Known for years (89.3% [266/298]; BIORad; p20) Review/Change interpretative criteria…Harmonize international criterias Combine wb interpretative criteria eg: CDC/ASTPHLD + WHO [Tebourski et al, 2004] License new tests (eg. LIA) – patent issues ? LIA – test of choice in NLHRS sens (100% vs 95%), spec (94% vs 65%) PPV (65% vs 22%), NPV (100% vs 99%)
Predictive Values Positive predictive value (PPV) PPV = TP/TP +FP (x 100) Negative predictive value (NPV) NPV = TN/TN+FN (x100) How accurately a test predicts the presence or absence of analyte (disease) ! (i) sensitivity - incidence of true positives in those with disease (ii) specificity - incidence of true of negatives in those without disease (iii) prevalence - number of actual cases (of disease) in the population. Galen RS and Gambino SR. Beyond Normality: The Predictive Value and Efficiency of Medical Diagnosis. New York: Wiley, 1975. OMIT SLIDE ???