Review of Current COVID-19 Diagnostics and Opportunities for Further Development

Abstract

Diagnostic testing plays a critical role in addressing the coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Rapid and accurate diagnostic tests are imperative for identifying and managing infected individuals, contact tracing, epidemiologic characterization, and public health decision making. Laboratory testing may be performed based on symptomatic presentation or for screening of asymptomatic people. Confirmation of SARS-CoV-2 infection is typically by nucleic acid amplification tests (NAAT), which requires specialized equipment and training and may be particularly challenging in resource-limited settings. NAAT may give false-negative results due to timing of sample collection relative to infection, improper sampling of respiratory specimens, inadequate preservation of samples, and technical limitations; false-positives may occur due to technical errors, particularly contamination during the manual real-time polymerase chain reaction (RT-PCR) process. Thus, clinical presentation, contact history and contemporary phyloepidemiology must be considered when interpreting results. Several sample-to-answer platforms, including high-throughput systems and Point of Care (PoC) assays, have been developed to increase testing capacity and decrease technical errors. Alternatives to RT-PCR assay, such as other RNA detection methods and antigen tests may be appropriate for certain situations, such as resource-limited settings. While sequencing is important to monitor on-going evolution of the SARS-CoV-2 genome, antibody assays are useful for epidemiologic purposes. The ever-expanding assortment of tests, with varying clinical utility, performance requirements, and limitations, merits comparative evaluation. We herein provide a comprehensive review of currently available COVID-19 diagnostics, exploring their pros and cons as well as appropriate indications. Strategies to further optimize safety, speed, and ease of SARS-CoV-2 testing without compromising accuracy are suggested. Access to scalable diagnostic tools and continued technologic advances, including machine learning and smartphone integration, will facilitate control of the current pandemic as well as preparedness for the next one.

Management of COVID-19 Patients in the Emergency Department

“…Generally, NAATs are believed to be the most sensitive methods for a pathogen detection [ 55 , 56 ] whereas RDTs are recommended by the World Health Organization (WHO) mainly in research and low-income countries [ 57 ]. RT-PCR is recommended as the most sensitive NAAT method [ 55 , 56 ]. Like all diagnostic tests, rRT-PCR is not completely foolproof and false-negativity has been reported.…”

“…Like all diagnostic tests, rRT-PCR is not completely foolproof and false-negativity has been reported. False negatives have been reported to occur in ∼30% (range 10–40%) of patients with COVID-19 [ 56 , 58 ]. Multiple factors may contribute to false RT-PCR results, including: (1) a high limit of detection score (LoD score) in a specific RT-PCR kit; (2) sample collection when the viral load is low (e.g., early after exposure and before the peak associated with symptom onset, or late in disease course); (3) faulty sample collection technique especially from unqualified personnel resulting in reduced viral specimens and load; (4) sample degradation from inadequate preservation, delays in transportation, and processing of the unstable RNA virus, as specimens may degrade without appropriate transport medium or storage conditions; (5) specific SARS-CoV-2 RNA mutations that escape detection; (6) RT-PCR inhibitors in the sample (bloody or viscous sample, such as in several respiratory preexisting medical conditions); (7) technical limitations of the RT-PCR kit’s interim guidance [ 57 , 58 ].…”

“…The aforementioned molecular two-step assay usually takes 3.5–4.0 h [ 62 ]. Thus, point-of-care (POC) tests are currently being implemented, and they provide results within minutes rather than hours [ 56 ]. These may be NAAT, Ag-RDTs, or antibody tests.…”

“…These may be NAAT, Ag-RDTs, or antibody tests. Most molecular POC tests that are currently used or recently developed demonstrate excellent accuracy with 96–100% PPV and similar negative predictive value (NPV) [ 56 ]. In regard to Ag-RDTs, data showed excellent specificity (99.5–100%) and varying overall sensitivity (11.7–68.8%) directly associated with viral loads [ 56 , 63 ].…”

“…Most molecular POC tests that are currently used or recently developed demonstrate excellent accuracy with 96–100% PPV and similar negative predictive value (NPV) [ 56 ]. In regard to Ag-RDTs, data showed excellent specificity (99.5–100%) and varying overall sensitivity (11.7–68.8%) directly associated with viral loads [ 56 , 63 ]. In a recently published study by Jegerlehner et al, concerning the diagnostic accuracy of a SARS-CoV-2 rapid antigen test in real-life clinical settings, the overall sensitivity of the rapid antigen test was 65.3% (95% confidence interval [CI] 56.8–73.1), the specificity was 99.9% (95% CI 99.5–100.0), while in asymptomatic individuals, the sensitivity was 44.0% (95% CI 24.4–65.1) [ 64 ].…”