- Clinical Guidance
- NIH Recommendations for Testing for SARS-CoV-2 Infection
- SARS-CoV-2 Testing for Public Health Use: Core Principles and Considerations for Defined Use Settings
- CDC Guidance for SARS-CoV-2 Point-of-Care Testing
- CDC Interim Guidance for Antigen Testing for SARS-CoV-2
- CDC Interim Guidelines for COVID-19 Antibody Testing
- Interim Guidelines for Collecting, Handling, and Testing Clinical Specimens for COVID-19
- FDA FAQs on Testing for SARS-CoV-2
- NEJM Video: How to Obtain a Nasopharyngeal Swab Specimen (Diagram)
- Research
- Diagnostics for SARS-CoV-2 Infections (Feb 2021)
- Interpreting Diagnostic Tests for SARS-CoV-2
- COVID-19 Testing: One Size Does Not Fit All
- Nucleic Acid Amplification Testing
- Woloshin S, et al. False Negative Tests for SARS-CoV-2 Infection — Challenges and Implications. N Engl J Med. Aug 2020.
- Wikramaratna PS, et al. Estimating False-negative Detection Rate of SARS-CoV-2 by RT-PCR. Euro Surveill. Dec 2020.
- Higgins TS, et al. SARS-CoV-2 Nasopharyngeal Swab Testing—False-Negative Results From a Pervasive Anatomical Misconception. JAMA Otolaryngol Head Neck Surg. Sep 2020.
- Sullivan CB, et al. Cerebrospinal Fluid Leak After Nasal Swab Testing for Coronavirus Disease 2019. JAMA Otolaryngol Head Neck Surg. Oct 2020.
- Collier DA, et al. Point of Care Nucleic Acid Testing for SARS-CoV-2 in Hospitalized Patients: A Clinical Validation Trial and Implementation Study. Cell Rep Med. Nov 2020.
- Gibani MM, et al. Assessing a Novel, Lab-Free, Point-of-Care Test for SARS-CoV-2 (CovidNudge): A Diagnostic Accuracy Study. Lancet Microbe. Nov 2020.
- Atherstone C, et al. Time from Start of Quarantine to SARS-CoV-2 Positive Test Among Quarantined College and University Athletes — 17 States, June–October 2020. MMWR Morb Mortal Wkly Rep. Jan 2021.
- Cycle (Ct) Thresholds
- CEBM: COVID-19 Testing and Correlation with Infectious Virus, Cycle Thresholds, and Analytical Sensitivity
- Salvatore PP, et al. Epidemiological Correlates of PCR Cycle Threshold Values in the Detection of SARS-CoV-2. Clin Infect Dis. Sep 2020.
- Hay JA, et al. Estimating Epidemiologic Dynamics from Single Cross-Sectional Viral Load Distributions. Oct 2020. (Not Peer Reviewed)
- Pooled Testing
- Barak N, et al. Lessons from Applied Large-Scale Pooling of 133,816 SARS-CoV-2 RT-PCR Tests. Sci Transl Med. Feb 2021.
- Cleary B, et al. Using Viral Load and Epidemic Dynamics to Optimize Pooled Testing in Resource-Constrained Settings. Sci Transl Med. Feb 2021.
- Antigen Testing
- Pekosz A, et al. Antigen-Based Testing but Not Real-Time Polymerase Chain Reaction Correlates With Severe Acute Respiratory Syndrome Coronavirus 2 Viral Culture . Clin Infect Dis. Jan 2021.
- Prince-Guerra JL, et al. Evaluation of Abbott BinaxNOW Rapid Antigen Test for SARS-CoV-2 Infection at Two Community-Based Testing Sites — Pima County, Arizona, November 3–17, 2020. MMWR Morb Mortal Wkly Rep. Jan 2021.
- Pilarowski G, et al. Performance Characteristics of a Rapid SARS-CoV-2 Antigen Detection Assay at a Public Plaza Testing Site in San Francisco. J Infect Dis. Jan 2021.
- Schwob JM, et al. Antigen Rapid Tests, Nasopharyngeal PCR and Saliva PCR to Detect SARS-CoV-2: A Prospective Comparative Clinical Trial. Nov 2020. (Not Peer Reviewed)
- Serological Testing
- Cheng MP, et al. Serodiagnostics for Severe Acute Respiratory Syndrome-Related Coronavirus 2 : A Narrative Review. Ann Intern Med. Sep 2020.
- Lisboa Bastos M, et al. Diagnostic Accuracy of Serological Tests for COVID-19: Systematic Review and Meta-analysis. BMJ. Jul 2020.
- Whitman JD, et al. Evaluation of SARS-CoV-2 Serology Assays Reveals a Range of Test Performance. Nat Biotechnol. Aug 2020.
- Adams ER, et al. Antibody Testing for COVID-19: A Report from the National COVID Scientific Advisory Panel. Wellcome Open Res. Jun 2020.
- Specimen Type (NP Swab vs Saliva) and Collection
- Bastos ML, et al. The Sensitivity and Costs of Testing for SARS-CoV-2 Infection With Saliva Versus Nasopharyngeal Swabs. Ann Intern Med. Jan 2021.
- Butler-Laporte G, et al. Comparison of Saliva and Nasopharyngeal Swab Nucleic Acid Amplification Testing for Detection of SARS-CoV-2: A Systematic Review and Meta-analysis. JAMA Intern Med. Jan 2021.
- Yokota I, et al. Mass Screening of Asymptomatic Persons for SARS-CoV-2 Using Saliva. Clin Infect Dis. Sep 2020.
- Babady NE, et al. Performance of SARS-CoV-2 Real-Time RT-PCR Tests on Oral Rinses and Saliva Samples. J Mol Diagn. Nov 2020.
- Wyllie AL, et al. Saliva or Nasopharyngeal Swab Specimens for Detection of SARS-CoV-2. N Engl J Med. Sep 2020.
- McCulloch DJ, et al. Comparison of Unsupervised Home Self-collected Midnasal Swabs With Clinician-Collected Nasopharyngeal Swabs for Detection of SARS-CoV-2 Infection. JAMA Netw Open. Jul 2020.
- Other
- Ning B, et al. A Smartphone-Read Ultrasensitive and Quantitative Saliva Test for COVID-19. Sci Adv. Jan 2021.
- Larremore DB, et al. Modeling the Effectiveness of Olfactory Testing to Limit SARS-2-CoV Transmission. Dec 2020. (Not Peer Reviewed)
- Basile K, et al. Cell-Based Culture of SARS-CoV-2 Informs Infectivity and Safe De-Isolation Assessments during COVID-19.Clin Infect Dis. Oct 2020.
- Antigen tests (also known as rapid tests) are diagnostic tests and not screening tests for patients with signs or symptoms consistent with COVID-19. Antigen tests are not as sensitive as nucleic acid amplification (including PCR) tests, there is a higher chance of false negatives, thus negative results do not rule out infection and may need to be confirmed with a nucleic acid amplification testing prior to making treatment or isolation decisions (see CDC Testing Basics).
- Testing throat and nasal swabs by RT-PCR is not guaranteed to yield a positive result for SARS-CoV-2 infection and this probability decreases with time since the onset of symptoms. In a single test of someone who first developed symptoms ten days ago, there’s a 33% chance of a false negative with a nasopharyngeal swab and 53% chance of a false negative with an oropharyngeal swab.
- Molecular detection of SARS-CoV-2 RNA does not mean infectious virus is present. The use of Ct values and clinical symptoms in combination with PCR testing for SARS-CoV-2 provides a more accurate assessment of the potential for infectious virus shedding.
- Cycle threshold (Ct) values are lowest (corresponding to higher viral RNA concentration) soon after symptom onset and are significantly correlated with time elapsed since onset (P<0.001); within 7 days after symptom onset, the median Ct value was 26.5 compared with a median Ct value of 35.0 occurring 21 days after onset. Ct values were significantly lower among participants under 18 years of age (P=0.01) and those reporting upper respiratory symptoms at the time of sample collection (P=0.001) and were higher among participants reporting no symptoms (P=0.05). (Science Magazine Summary)
- The correlation between SARS-CoV-2 antigen and SARS-CoV-2 culture positivity represents a significant advancement in determining the risk for potential transmissibility beyond that which can be achieved by detection of SARS-CoV-2 genomic RNA.
- Sensitivity of the BinaxNOW antigen test, compared with polymerase chain reaction testing, was lower when used to test specimens from asymptomatic (35.8%) than from symptomatic (64.2%) persons, but specificity was high. Sensitivity was higher for culture-positive specimens (92.6% and 78.6% for those from symptomatic and asymptomatic persons, respectively); however, some antigen test-negative specimens had culturable virus.
- The high performance of rapid diagnostic [antigen] tests allows rapid identification of COVID cases with immediate isolation of the vast majority of contagious individuals.
- SARS-CoV-2 testing on respiratory specimens has imperfect sensitivity and is limited in capacity. Antibody testing can aid in diagnosing RT-PCR–negative patients who present later during disease. However, antibody testing should not be the only test for diagnosing acute COVID-19.
- Pooled sensitivity from 40 studies was 84.3% for enzyme-linked immunosorbent assays measuring IgG or IgM, 66.0% for lateral flow immunoassays (LFIAs), and 97.8% for chemiluminescent immunoassays. The pooled sensitivity of LFIAs was lower in commercial kits compared with non-commercial tests. The sensitivity at week 3 after symptom onset was significantly higher than at week 1.
- Test specificity ranged from 84.3% to 100.0% and was predominantly affected by variability in IgM results. LFA specificity could be increased by considering weak bands as negative, but this decreased detection of antibodies (sensitivity) in a subset of SARS-CoV-2 real-time PCR-positive cases. Our results underline the importance of seropositivity threshold determination and reader training for reliable LFA deployment (Explore their Dataset).
- Currently available commercial LFIA devices do not perform sufficiently well for individual patient applications. ELISA can be calibrated to be specific for detecting and quantifying SARS-CoV-2 IgM and IgG and is highly sensitive for IgG from 10 days following first symptoms.
- “Thirty-seven studies with 7,332 paired samples were included. The sensitivity of saliva was 3.4 percentage points lower than that of nasopharyngeal swabs. Among persons with previously confirmed SARS-CoV-2 infection, saliva’s sensitivity was 1.5 percentage points higher than that of nasopharyngeal swabs. Among persons without a previous SARS-CoV-2 diagnosis, saliva was 7.9 percentage points less sensitive. In this subgroup, if testing 100,000 persons with a SARS-CoV-2 prevalence of 1%, nasopharyngeal swabs would detect 79 more persons with SARS-CoV-2 than saliva, but with an incremental cost per additional infection detected of $8,093.”
- Both nasopharyngeal and saliva specimens had high sensitivity and specificity.
- In this small study, researchers compared home-collected versus clinician-collected nasopharyngeal swabs for COVID-19 testing. The two methods were comparable.
- The authors describe an ultrasensitive saliva-based COVID-19 assay with a 15-minute sample-to-answer time that does not require RNA isolation or laboratory equipment. This assay uses CRISPR-Cas12a activity to enhance a viral amplicon signal, which is stimulated by the laser diode of a smartphone-based fluorescence microscope device. This device robustly quantified viral load over a broad linear range and exhibited a limit of detection below that of the PCR gold standard assay. CRISPR data of SARS-CoV-2 RNA levels were similar in saliva and nasal swabs, and viral loads measured by RT-PCR and the smartphone-read CRISPR assay demonstrated good correlation.
- Evaluation of an alternative strategy based on the monitoring of olfactory dysfunction, a symptom identified in 76-83% of SARS-CoV-2 infections—including those that are otherwise asymptomatic—when a standardized olfaction test is used. The authors model how screening for olfactory dysfunction, with reflexive molecular tests, could be beneficial in reducing community spread of SARS-CoV-2 by varying testing frequency and the prevalence, duration, and onset time of olfactory dysfunction and believe that self-monitoring olfactory dysfunction could reduce spread via regular screening.
- SARS-CoV-2 culture may be used as a surrogate marker for infectivity and inform de-isolation protocols.