Lab Matters Summer 2018 | Page 68

APHL 2018 Annual Meeting Poster Abstracts

Infectious Disease

Background : Routine detection of Measles , Mumps , Rubella and Varicella Zoster ( MMRV ) IgG is used to determine antibody status where infection history or previous immunization is unknown .

Materials / Methods : This MMRV assay was developed using the Dynex Technologies Multiplier system and coated bead technology . Antigen coated beads representing each MMRV specificity were embedded into the base of carrier 96 well assay plate . Each assay well contains the 4 MMRV targets for the test sample IgG detection . The final chemiluminescent reaction is imaged with the on-board camera and results output as index values referenced against the assay specific calibrator . Precision was measured by assaying a range of 14 samples 3 times across an assay plate on three instruments over three days . A ROC analysis was run in order to set the cut-off for each of MMV and confirm it for Rubella where the cutoff was ultimately defined by the International reference RUBI-1-94 . Based on the resulting cut-off values , concordance was assessed on up to 929 samples collected for MMRV screening ; results were compared to 510k cleared ELISA assays .

Results : Percentage coefficient of variation (% CV ) for each MMRV specificity was calculated and is summarized below :

Precision test Measles (% CV ) Mumps (% CV ) Rubella (% CV ) VZV (% CV ) Within run 4.54 5.35 3.69 4.08 Between run 4.51 5.66 4.64 4.06 Between day 3.56 4.01 4.76 3.15 Between instrument 1.41 3.19 2.24 1.37

ROC analysis :

Area under the curve ( AUC ) and 95 % confidence interval ( CI ) results were :

• Measles 0.995 AUC ( 0.991-0.998 CI )

• Mumps 0.987 AUC ( 0.977-0.997CI )

• Rubella 0.998 ( 0.997-0.999 CI )

• VZV 0.999 ( 0.997-1.000 CI ).

• Percent positive agreement ( PPA ) and percent negative agreement ( PNA ) with 95 % confidence intervals ( Cl ) were calculated in two ways :

• Equivocal samples scored as positive PPA : Measles - 95.3 % ( 93.5-96.6 %), Mumps : 90.2 ( 87.8-92.2 %), Rubella : 93.9 ( 91.9-95.4 %), VZV : 98.1 ( 96.8-98.8 %). PNA : Measles – 94.2 ( 90.7-97.0 %), Mumps : 93.3 ( 88.5-96.2 %), Rubella 99.5 % ( 97.4- 99.9 %), VZV 97.5 ( 96.3-99.2 %).

• Equivocal samples scored as negative PPA : Measles – 93.3 % ( 91.2-95.0 %) Mumps : 93.3 ( 91.1-95.0 %), Rubella : 93.0 ( 90.9- 94.7 %), VZV : 97.7 ( 96.3-98.5 %). PNA : Measles – 95.4 ( 92.0- 97.4 %), Mumps : 94.6 ( 90.8-96.9 %), Rubella : 100.0 ( 98.4- 100.00 %), VZV : 99.2 ( 95.6-99.9 %).

Conclusion : This multiplexed fully automated assay gives reproducible semi-quantitative results for MMRV IgG . It is ideal for batch testing as can handle up to ninety two test samples in a single plate to produce 368 results in < 3 hours . When two plates are run together 736 results are generated in five hours .

Presenter : Robert Wolfert , PhD , Dynex Technologies , Inc ., Chantilly , VA , Phone : 703.803.1254 , Email : rwolfert @ dynex . com

Novel ELISA Based on Antigens from Strongyloides papillosus Instead of Strongyloides ratti Exhibits Increased Serological Specificity

B . Menge 1 , O . Klemens 1 , A . Streit 2 , O . Sendscheid 3 , J . Klemens 1 , K . Steinhagen 1 ; 1 EUROIMMUN , Lubeck , Germany , 2 Max Planck Institute for Developmental Biology , Tubingen , Germany , 3 EUROIMMUN US , Inc ., Mountain Lakes , NJ

Background : Strongyloidiasis is an infectious disease caused by the nematode Strongyloides . Human infection by Strongyloides stercoralis can manifest with dermatological , intestinal and pulmonal symptoms frequently passing into a chronic disease . Low parasitic loads and discontinuous larvae excretion may hamper diagnosis by coproscopy . Serological test systems are more sensitive to detect the infection . Available serological tests are commonly based on native antigens from S . ratti larvae and lack specificity . We developed and evaluated the first ELISA based on S . papillosus to increase specificity . Methods : Evaluation of the ELISA based on S . papillosus was performed using the following three approaches :[ 1 ] Participation in an external quality assessment scheme ( NEQAS , UK ) encompassing six positive and five negative samples [ 2 ] A correlation study with the commercial Bordier ELISA ( Strongyloides ELISA kit based on S . ratti antigens ; Bordier Affinity Products , Switzerland ) including 89 sera pre-characterized as either positive ( n = 59 ) or negative ( n = 30 ) by means of Bordier ELISA [ 3 ] Comparison with an in house ELISA based on S . ratti by determining specificity with respect to a cross-reactivity panel ( n = 193 , samples from patients with other parasitic or bacterial infections ) and a control panel ( n = 688 , samples from 500 healthy blood donors , 100 pregnant women and 88 children ).

Results : [ 1 ] Results obtained with the Anti-Strongyloides ELISA were 100 % in agreement with NEQAS target values .[ 2 ] In 74 of 89 samples ( 83.1 %), the result of the novel ELISA correlated with the Bordier ELISA . Seven discrepant cases , which were positive in Bordier ELISA but negative in the novel ELISA , were further examined . Serological analyses indicated the presence of antibodies against other parasites ( Plasmodium spp ., Schistosoma spp . and Echinococcus spp .) in six of these cases .[ 3 ] The S . ratti based ELISA was reactive in 13.9 % of the sera in the cross-reactivity panel and in 10.6 % of the samples from healthy individuals , yielding a combined specificity of 88.6 %. In comparison , reactivities of 6.2 % ( cross-reactivity panel ) and 3.5 % ( healthy individuals ) were detected with the novel Anti-Strongyloides ELISA , resulting in a combined specificity of 95.9 %.

Discussion : The novel Anti-Strongyloides ELISA reveals a high diagnostic accuracy in the serological diagnosis of Strongyloidiasis . The use of native antigens from S . papillosus instead of S . ratti increases assay specificity by 7.3 %.

Presenter : Oliver Sendscheid , PhD , EUROIMMUN US , Inc ., Mountain Lakes , NJ , Phone : 973.656.1000 x130 , Email : oliver . sendscheid @ euroimmun . us

Development of a Novel NS1-based ELISA for Detection of Specific IgG Antibodies Against West-Nile Virus

O . Klemens 1 , C . Pannwitt 1 , A . Hachid 2 , J . Klemens 1 , O . Sendscheid 3 , J . Fraune 1 , W . Schlumberger 1 , K . Steinhagen 1 ; 1 EUROIMMUN , Lubeck , Germany , 2 Institut Pasteur d ’ Algérie , Dely-Brahim , Algeria

3

EUROIMMUN US , Inc ., Mountain Lakes , NJ