Presentation on theme: "TESTS USED IN BLOOD SCREENING French Blood Services (EFS)"— Presentation transcript:
1 TESTS USED IN BLOOD SCREENING French Blood Services (EFS) Second WHO consultation on International Reference Preparation for Chagas Diagnostic TestsJanuary 27 & 28 January, 2009TESTS USED IN BLOOD SCREENINGdDr Azzedine ASSALFrench Blood Services (EFS)
2 BackgroundThe choice of a Chagas disease screening assay or strategy for TT prevention is far from straightforwardRecommendation of the PAHO (1994): parallel use of at least 2 different serological tests in Chagas disease screening in blood donations (Lack of sensitivity and specificity) .Recommendations of WHO, 2002: one ELISA is recommended for blood bank screening
3 Control of Chagas Disease Second report of the WHO expert Committee Geneva 2002
4 Amadeo Sáez-Alquezar. Fondation Mérieux. May 2008. Screening StrategiesEndemic Countries :Brazil: until 2002: 2 tests (>70% ELISA + IHA)Brazil: since 2003: 1 test ELISAArgentina 2004: 2 testsCosta Rica 2006: 2 tests (ELISA rec + Lys)Non endemic countriesUK 1999 to 2005: 1 ELISA Lys, from 2006 ELISA recUSA 2007: 1 test (ELISA Lys)France 2007: 2 tests (ELISA rec + Lys)Spain 2008: 2 tests (ELISA rec + Lys)The shift of Brazilian Blood Banks to One test is based on the fact that the PAHO recommendation for using to tests dates back to a period of time were tests lacked sensitivity. Nowadays tests has better performance and undergo a series of quality controls and regulation requirements that make them more reliable.Amadeo Sáez-Alquezar. Fondation Mérieux. May 2008.
5 Ideal screening serological test The ideal test does not exist 100 % sensitivity100 % specificityReproducibleEasy to performFast and automatedNon subjective readingNot expensiveThe ideal test does not exist
6 Different strategies for blood banks Using only one testHigh sensitivity test (IgG + IgM)Use a whole parasite Lysate test (mixture of parasite antigens)Using 2 tests1 Lysate ELISA + 1 rec ELISAIFI + ELISA
7 French Screening Strategy Commercial assays available : IHA or other agglutination tests, ELISA, IFA.French strategy: Screening based on 2 parallel ELISAs (Crude and recombinant antigens).IFA as an alternative test (“confirmation”) test in case of positivity or discrepancy between the 2 ELISAs.
8 EVALUATED ASSAYS 1) ELISAs Recombinant ELISAs Bioelisa Chagas (Biokit, Spain). CE mark.Crude ELISAsELISA Cruzi (BioMérieux). No CE mark.Chagatek Elisa (Lemos, Argentina), No CE mark.T.cruzi ELISA Test System–1 (OCD). CE mark.EIAgen Trypanosoma Cruzi Ab (manufactured by Adaltis and distributed by Ingen,France). CE mark.2) IFAImmunofluor Chagas (Biocientifica. Argentina). CE mark.
9 FEASIBILITY CLINICAL SENSITIVITY SPECIFICITY EVALUATED FEATURES REPRODUCIBILITY
10 Reference material for test evaluation IdeallySensitivity evaluationStrong positive samplesBorderline samplesDiscordant samplesSamples with reactivity against main strains of the 2 lineages of T. cruziSpecificity evaluation“True” negative samplesPotential cross-reactive samples (leishmania, T. Rangeli, other protozoans)
11 Material and methods Panels and samples BBI panel : 14 positive samples + 1 negative sampleDilutions of Positive Control (Accurun, Ingen)Brazilian donor Panel (Blood Bank Sao Paulo): 36 samples of positive and negative donors, tested with ELISA, IHA et IFA.Patient samples (French Guyana) 35 positive and negative samples, tested with ID PaGia (Diamed), Biokit ELISA and PCRFrench Blood donors for specificity study.
12 RESULTS Sensitivity / BBI Panel The 14 samples are detected positive by all the kits.
13 Sensitivity / Brazilian donor panel RESULTS (2)Sensitivity / Brazilian donor panelNegative samples: No discrepancies with Brazilian data.
14 Sensitivity / Brazilian donor panel RESULTS (3)Sensitivity / Brazilian donor panel24 non negative samples20 positives in concordance with Brazilian data.4 discrepant samples.
15 Sensitivity / Brazilian donor panel RESULTS (4)Sensitivity / Brazilian donor panelThe 4 discrepant results of Brazilian lab are discrepant with EFS tests as well
16 Conclusion on the sensitivity of Brazilian donor panel RESULTS (5)Conclusion on the sensitivity of Brazilian donor panelGood overall sensitivity of all the kitsFollow up of Brazilian discrepant samples showed that the discrepant samples were false positive samples
17 RESULTS (6) Guyana patient samples A set of 35 negative and positive patient samples (Dr Christine Aznar. Laboratory of Parasitology, Cayenne Hospital, French Guyana).Tested by 3 different assays in Guyana:Agglutination test (ID-PaGIA, Diamed, France).ELISA (Bioelisa Chagas, Biokit).In-house PCR.Blind testing before result comparison with Guyana data.
18 Guyana patient samples (2) Out of the 35 samples tested:10 samples negative in agreement with Guyana's results7 samples could not be interpreted (incomplete data)18 samples expected to be positive according to Guyana’sdata.
19 Reproducibility Dilution series of Accurun Tested in 8 replicates per run, during 3 different days (24 values)
20 Tested on a limited number of donations (limited number of kits). SpecificityTested on a limited number of donations (limited number of kits).
27 Measures taken to prevent T. cruzi Transfusion transmitted infections. Temporary deferral, for 4 months oftravelers or residents returning from endemicareas.Screening for antibodies to T. cruzi intargeted at risk blood donors.
28 Donors born in endemic areas Travelers and residents returning from At risk blood donorsDonors born in endemic areasTravelers and residents returning fromendemic areasDonors born in France from a mother born inrisk areasDonors who underwent blood transfusion
30 Seroprevalence in French Donors Period: May 2, 2007 to February 29, 2008Collected donationsTested donationsNegative donationsPositive donationsInconclusive resultsNumber of donations(Percentage)2,143,74097,618(4.55 %)96,625(99 %)4(0,004 %)1 / 24,404989(1 %)dN.B.= Seroprevalence in UK: 1/ 24,300 from 1999 to 2007
31 Positive Donors in France 2 first-time Bolivian donors2 donors from San SalvadorOne first-time donorOne repeat donor: only 2 previous donations transfused to recipients who died from underlying diseases.d
33 Control of French Inconclusive results 465 donors with inconclusive results could be controlled.Out of these 213 (46 %) were found negative.d
34 Reevaluation of Ortho test Tobler LH et al. Evaluation of a new enzyme-linked immunosorbent assay for detection of Chagas antibody in US blood donors. Transfusion January 2007;47:90-96d
35 Reevaluation of Ortho test Cut off calculation of Ortho test modified: better sensitivitySame sensitivity with BBI panel and Brazilian samplesGood sensitivity with 53 Mexican samples: higher S/CO than those obtained with BioMérieux and Biokit kitsSpecificity evaluated on 4000 donations:1 non repeated reactive sample2 repeat reactive samples (specificity: % )d
36 Reevaluation of Ortho test Patient panelOnly 4 samples leftSamplesS/CO 2006S/CO 2009BioMérieuxBiokitOrthoVTLA1.222.540.6021.36VTJE1.661.460.5461.23Da Sis3.190.3461.03VTVE2.911.010.8361.70d
37 Conclusions Current serological tests (ELISAs) have good performance Performance continuously improved by manufactures under stringent Quality Control proceduresCurrent screening strategy results in Large number of Indeterminate results (false positive ?).IFA is used in France as an alternative tests. It is cumbersome, with a subjective reading and interpretation and with analytical performance close to ELISAs, it should be replaced by a real confirmatory test such as WB or IB)
38 Conclusions (2) Revision of screening strategy in France Screening strategy should be simplifiedScreening with a single ELISA sufficientReplace IFA by true confirmatory assays (Western Blot, immunoblot , RIPA,…)IFA is used in France as an alternative tests. It is cumbersome, with a subjective reading and interpretation and with analytical performance close to ELISAs, it should be replaced by a real confirmatory test such as WB or IB)Sreening with only one ELISA in a non endemic country with few immigrants from endemic countries is sufficient provided the test has good sensitivity and specificity