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Capacity-Responsive COVID-19 Testing Performance in Emergency Departments: Turnaround Time Thresholds for Lateral Flow Assay and Polymerase Chain Reaction Strategies

Published online by Cambridge University Press:  16 June 2026

Cheng-Han Chen Open the ORCID record for Cheng-Han Chen [Opens in a new window] ,
Yi-Tzu Lee ,
Li-Hua Li ,
Teh-Fu Hsu ,
Chorng-Kuang How  and
Chao-Min Cheng
Cheng-Han Chen*
Affiliation:
Emergency Department, Taipei Veterans General Hospital, Taipei, Taiwan School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
Yi-Tzu Lee
Affiliation:
Emergency Department, Taipei Veterans General Hospital, Taipei, Taiwan School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
Li-Hua Li
Affiliation:
Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
Teh-Fu Hsu
Affiliation:
Emergency Department, Taipei Veterans General Hospital, Taipei, Taiwan Department of Emergency Medicine, Kinmen Hospital, Ministry of Health and Welfare, Kinmen, Taiwan Institute of Emergency and Critical Care Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan School of Nursing, National Yang Ming Chiao Tung University, Taipei, Taiwan
Chorng-Kuang How
Affiliation:
Emergency Department, Taipei Veterans General Hospital, Taipei, Taiwan School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
Chao-Min Cheng*
Affiliation:
Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu, Taiwan
*
Correspondence: Cheng-Han Chen, MD, PhD Taipei Veterans General Hospital, Taipei, Taiwan E-mail: gdc123.tw@gmail.com; Chao-Min Cheng, PhD, Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu, Taiwan E-mail: chaomin@mx.nthu.edu.tw
Correspondence: Cheng-Han Chen, MD, PhD Taipei Veterans General Hospital, Taipei, Taiwan E-mail: gdc123.tw@gmail.com; Chao-Min Cheng, PhD, Institute of Biomedical Engineering, National Tsing Hua University, Hsinchu, Taiwan E-mail: chaomin@mx.nthu.edu.tw
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Abstract

Background:

During the coronavirus disease 2019 (COVID-19) pandemic, emergency departments (EDs) faced unprecedented operational stress compounded by mandatory testing requirements that directly influenced patient flow and length-of-stay (LOS). Two testing modalities were central to pandemic ED operations: (1) rapid point-of-care lateral flow assays (LFAs), which return results in minutes but depend on frontline ED personnel and space, and (2) laboratory-based polymerase chain reaction (PCR), which requires sample transport and centralized processing but functions independently of ED capacity. Whether the relative performance of these modalities remains robust under varying ED operational pressures is unclear.

Methods:

This retrospective observational study analyzed 31,737 COVID-19 testing encounters (11,098 LFA; 20,639 PCR) during the 11-month dual-testing period (May 2022–March 2023) at a high-volume tertiary ED, when both modalities were concurrently deployed. Propensity score matching (PSM; 1:1 nearest-neighbor, caliper 0.5 SD) generated 8,492 well-balanced LFA–PCR pairs. Turnaround time (TAT) was evaluated as an operational stress indicator modifying the association between testing modality and ED LOS. Variability analyses assessed performance stability under differing capacity levels.

Results:

Overall, LFA was associated with longer LOS than PCR (median 8.3 versus 5.8 hours; P < 0.001). Under low-stress conditions (TAT ≤30 minutes), this difference was modest (median difference 1.5 hours; 95% CI, 0.80 to 2.07). As TAT increased, modality performance diverged substantially. At TAT >90 minutes, LOS difference increased to 3.6 hours (95% CI, 2.85 to 4.42). Threshold inflection occurred between 60–90 minutes. Lateral flow assays exhibited higher operational variability (CV ratio 2.09; 95% CI, 1.25 to 3.12), with the greatest instability during high-volume periods, while PCR performance remained comparatively stable across stress levels. Stratified analyses were exploratory; confidence intervals were not adjusted for multiplicity.

Conclusion:

Turnaround time and its variability serve as actionable, real-time indicators of ED system capacity. Lateral flow assay performance degrades progressively under operational strain due to its reliance on frontline ED resources, whereas PCR—supported by external laboratory infrastructure—maintains more stable throughput. Capacity-contingent, adaptive testing strategies that shift toward PCR as TAT rises may enhance ED resilience, reduce LOS, and support more predictable patient flow during future outbreaks and surge conditions.

Keywords

COVID-19emergency departmentlateral flow assaypoint-of-care testingpolymerase chain reactionturnaround time

Information

Type
Original Research
Information
Prehospital and Disaster Medicine , Volume 41 , Issue 1 , 2026 , e10
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Copyright
© The Author(s), 2026. Published by Cambridge University Press on behalf of World Association for Disaster and Emergency Medicine

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