Lab Matters Summer 2018 | Page 73

APHL 2018 Annual Meeting Poster Abstracts

rRT-PCR, three were positive for dengue type 1 virus( 0.21 %) and one was positive for chikungunya virus( 0.07 %). NYC PHL’ s rapid response and testing flexibility enabled NYC to better monitor and manage the ZIKV outbreak.

Presenter: Bisram Deocharan, PhD, New York City Public Health Laboratory, New York, NY, Phone: 212.671.5734, Email: bdeochar @ health. nyc. gov

Zika Virus Antibody Testing Using the DiaSorin LIAISON XL Zika Capture IgM Assay

D. Liu 1, V. Streva 2, W. Ren 2, M. Younis 2, R. Basea 2, H. Doo 2, S. Sayeed 2, M. Moy 2, A. Dupuis 2, L. Kramer 2, A. Shukla 3, R. Limberger 2, J. Rakeman 1; 1 New York City Public Health Laboratory, New York, NY, 2 New York City Department of Health and Mental Hygiene, New York, NY, 3 Diasorin, Inc., Stillwater, MN

HON. MENTION 2018

Zika virus has spread through the Americas and the outbreak has been declared a public health emergency by the WHO. Because of the risk of harm to the fetus, rapid and accurate diagnosis of Zika virus infection is critical. Definitive diagnosis can be made by detection of Zika virus-specific RNA, however the viremic period is short and may be missed. Serology is a critical diagnostic and commonly includes a screening test for Zika IgM followed by PRNT. This study compared two methods used to screen for Zika IgM: a high-throughput DiaSorin LIAISON XL Zika Capture IgM and the CDC MAC-ELISA using 583 specimens. The CDC MAC-ELISA assay uses a pan-flavivirus antibody, 6b6c-1 and Zika virus E glycoprotein, which likely results in a high level of cross-reactivity with other flaviviruses. The LIAISON XL Zika Capture IgM uses a Zika NS1 peptide antigen that is more specific to Zika virus and less subject to the effects of non-specific binding by antibodies against other related flaviviruses. This first comprehensive analysis provides evidence for reproducible results and improved clinical testing sensitivity. Compared to the CDC MAC-ELISA, the LIAISON XL Zika Capture IgM Assay has a 95.2 % negative agreement, a 69.1 % positive agreement and an overall agreement of 78.0 %. The 69.1 % positive agreement is likely due to differences in testing methodology resulting in non-specific flavivirus IgM cross-reactivity in the CDC MAC-ELISA. About 80 % of the discrepant specimens were PRNT positive for Zika and dengue. This difference was further investigated by testing the discrepant specimens with the EuroImmun Zika IgM assay which also uses Zika NS1 protein and PRNT. The overall agreement between the LIAISON XL Zika Capture IgM and the EuroImmun Zika IgM was 97.8 % supporting the accuracy of the LIAISON XL Zika Capture IgM assay testing results. All of the specimens with inconclusive results from the CDC MAC-ELISA test had negative results on the LIAISON XL Zika Capture IgM assay, indicating that CDC MAC-ELISA specimens with inconclusive results likely represent true Zika IgM negatives with nonspecific interference causing a non-negative result on the CDC MAC-ELISA. Additionally, our data show that 50 out of 132 total equivocal CDC MAC-ELISA specimens were positive for Zika virus IgM when tested using the LIAISON XL Zika Capture IgM, suggesting an improved clinical testing sensitivity for the LIAISON XL Zika Capture IgM assay, allowing for a definitive result with a decreased turnaround time. Finally, the LIAISON XL Zika Capture IgM Assay has a Zika IgM intra-run precision of 2.4 % of 66578.9 RLU and an inter-run precision of 4.1 % of 66117.2 RLU. The LIAISON XL Zika Capture IgM will be a useful tool for laboratories to differentiate Zika virus infections from infections with other flaviviruses and will enable more rapid serological testing of potential Zika virus infected patients.

Presenter: Dakai Liu, PhD, New York City Public Health Laboratory, New York, NY, Phone: 212.447.2858, Email: dliu @ health. nyc. gov

Impact of Rapid Mycobacterium tuberculosis Complex Identification on Turnaround Time and Drug Resistance Predictions at the New York City Public Health Laboratory

J. Lemon, C. Courtney, Q. Liu and J. Rakeman, New York City Public Health Laboratory, New York, NY

New York City encounters an above average rate of tuberculosis cases, 6.9 per 100,000 people in 20161; most cases are in foreign born individuals. The NYC Public Health Laboratory( PHL) serves as the primary diagnostic testing laboratory for Health Department Chest Center clinics and tests approximately 5000 primary specimens per year. PHL also performs testing on ~ 600 referral isolates per year. The development of rapid molecular testing options for the diagnosis of Mycobacterium tuberculosis complex( MTBC) from primary patient specimens has presented an exciting opportunity to decrease diagnostic turnaround time( TAT), which has long been a challenge in the field. In this study, we evaluated the impact of implementing the Cepheid GeneXpert MTB / RIF assay in place of the HAIN GenoType MTBDR Line Probe Assay for molecular detection of MTBC. Molecular testing is routinely performed on smear positive primary specimens only. We retrospectively analyzed results from HAIN Line Probe assays performed in 2016. This set included data from 315 specimens from 290 patients, of which 110 were positive for MTBC by the HAIN Line Probe assay. One advantage of the HAIN Line Probe Assay is its ability to detect mutations associated with resistance to both rifampin( RIF) and isoniazid( INH). In contrast, the Xpert MTB / RIF assay detects mutations only associated with RIF resistance. Therefore, we analyzed the 110 MTBC positive specimens to determine the percentage of INH mono-resistance detected by the Hain Line Probe Assay and found that for one year of testing, only five patients( 4.5 %) had INH mono-resistance which would have been missed by the Xpert MTB / RIF Assay. We also evaluated the impact of switching assays on TAT for reporting molecular results. The HAIN Line Probe Assay required seven hours of personnel time, which was typically completed the day after reporting a positive microscopy result. Implementation of the Xpert MTB / RIF Assay would decrease personnel time from seven hours to > 1 hour, affording the opportunity for molecular testing to be completed on the same day as microscopy. This would allow for the release of a preliminary report a full working day earlier than the current algorithm allows. We determined that by performing an IQCP we would be able to meet regulatory requirements and discontinue the practice of performing daily quality control. This allowed the change of testing assays to have a minimal impact on cost despite the difference in cost between the two test kits. Our analysis demonstrates that implementation of a new molecular testing stratagem can result in minimal impact on drug resistance predictions, reduce TAT for results reporting, while maintaining overall testing costs and providing a viable solution for the future of MTBC molecular diagnostic testing in New York City.

1. New York City Department of Health and Mental Hygiene. Bureau of Tuberculosis Control Annual Summary, 2016.

Presenter: Jamie Lemon, PhD, D( ABMM), New York City Public Health Laboratory, New York, NY, Phone: 212.671.5668, Email: jlemon @ health. nyc. gov

Infectious Disease