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Predicting Direct-Specimen SARS-CoV-2 Assay Performance Using Residual Patient Samples.

Authors
  • Schroeder, Lee F1
  • Bachman, Michael A1
  • Idoni, Allison1
  • Gegenheimer-Holmes, Jennifer2
  • Kronick, Steven L2
  • Valdez, Riccardo1
  • Lephart, Paul R1
  • 1 Department of Pathology, University of Michigan, Michigan Medicine, Ann Arbor, MI, USA.
  • 2 Department of Emergency Services, University of Michigan, Michigan Medicine, Ann Arbor, Michigan, USA.
Type
Published Article
Journal
The journal of applied laboratory medicine
Publication Date
May 04, 2022
Volume
7
Issue
3
Pages
661–673
Identifiers
DOI: 10.1093/jalm/jfab159
PMID: 34755849
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Diagnostic sensitivities of point-of-care SARS-CoV-2 assays depend on specimen type and population-specific viral loads. Evaluation of these assays require "direct" specimens from paired-swab studies rather than more accessible residual specimens in viral transport media (VTM). Residual VTM and limit-of-detection studies were conducted on Abbott ID NOW™ COVID-19, Quidel Sofia 2™ SARS Antigen FIA, and DiaSorin Simplexa™ COVID-19 Direct assays, with cycle threshold (CT) adjustments to approximate direct-specimen testing based on gene-target doubling each PCR cycle. Logistic regression was used to model assay performance by specimen CT. These models were applied to CT distributions of symptomatic and asymptomatic populations presenting to emergency services to predict the percentage of specimens that would be detected by each assay. A 96-sample paired-swab study was conducted to confirm model results. When using direct nasopharyngeal samples and fit with either VTM or limit-of-detection data, percent positivities for ID NOW (symptomatic 94.9%/97.4%; asymptomatic 88.4.0%/89.6%) and Simplexa (symptomatic 97.8%/97.2%; asymptomatic 91.1%/90.8%) were predicted to be similar. Likewise, percent positivities for ID NOW with direct nasal specimens (symptomatic 77.8%; asymptomatic 64.5%) and, fit with VTM data, Sofia 2 with direct nasopharyngeal specimens (symptomatic 76.6%, asymptomatic 60.3%) were similar. The paired-swab study comparing direct nasopharyngeal specimens on ID NOW and nasopharyngeal VTM specimens on Simplexa showed 99% concordance. Assay performance can be modeled as dependent on viral load, fit using laboratory bench study results, and adjusted to account for direct-specimen testing. When using nasopharyngeal specimens, direct testing on Abbott ID NOW and VTM testing on DiaSorin Simplexa have similar performance. © American Association for Clinical Chemistry 2022. All rights reserved. For permissions, please email: [email protected]

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