COVID 19 Testing
Which Test is Right For Your Patients?
PCR IgM IgG Clinical Significance:
+ - - Patient may be in the window period of infection
+ + - Patient may be in the early stage of infection
+ + + .Patient is in the active phase of infection
+ - + Patient may be in the late or recurrent stage of infection
- + - Patient may be in the early stage of infection. PCR may be a false negative
- - + Patient may have had a past infection, and has recovered
- + + Patient may be in the recovery stage of an infection, or the PCR may be a false negative
Detection Method Limit of Detection
PCR testing - SARS-CoV-2 RNA 1 to 28 days post infection
IgM testing - Antibody Testing for IgM 7 to 21 days
IgG testing - Antibody Testing for IgG 14 to years - Long term immunity
Figure 1: This infection timeline is based on the current knowledge about the rise and fall
of COVID-19 RNA (SARS-CoV-2), IgM antibody and IgG antibody and the correlation of
these levels vary with the initial time of infection, onset of symptoms, and recovery phase.
Detection limits are based on average times for viral replication and average times for
IgG and IgM production. Detection limits may be different based on biological and viral
Sensitivity and Specificity of Assay
Sensitivity of 91.2% to 95.6%
Using RT-qPCR-confirmed SARS-CoV-2 positive specimens, the clinical sensitivity of the Diazyme DZ-Lite SARS-CoV-2 IgG CLIA test was estimated at 91.2%. When used in combination with the Diazyme DZ-Lite SARS-CoV-2 IgM CLIA test, clinical sensitivity was found to be 95.6%.
Specificity of 96%
Using confirmed SARS-CoV-2 negative specimens, the clinical specificity of the Diazyme DZ-Lite SARS-CoV-2 IgG CLIA test was estimated at 97.3%. When used in combination with the Diazyme DZ-Lite SARS-CoV-2 IgM CLIA test, clinical specificity was found to be 96.0%.
Using confirmed SARS-CoV-2 negative specimens, the clinical specificity of the Diazyme DZ-Lite SARS-CoV-2 IgM CLIA test was estimated at 97.5%. When used in combination with the Diazyme DZ-Lite SARS-CoV-2 IgG CLIA test, clinical specificity was found to be 96.5%.
People with COVID-19 have a wide range of reported symptoms, ranging from mild to severe illness. Symptoms may appear 2-14 days after exposure to the virus.
Shortness of breath or difficulty breathing
New loss of taste or smell
Less common symptoms may include:
When To Seek Medical Attention
Emergency warning signs for COVID-19. Please seek emergency medical care immediately if you have any of these symptoms:
Persistent pain or pressure in the chest
Inability to wake or stay awake
Blue-ish lips or face
This list is not all possible symptoms. Please call your medical provider for any other symptoms that are severe or concerning to you.
Who Can Get Tested
Testing will be based on Federal and State guidelines. California's guideline is categorized into two tiers:
Healthcare workers, first responders, and other social service employees
Any symptomatic person
People exposed to infected individuals in places where COVID-19 risk is high facilities including:
Asymptomatic residents or employees of group living
After positive cases have been identified in a facility
Before resident admission or re-admission to a facility
People in essential Jobs (Healthcare/Public Health, emergency services, food and agriculture, energy, water and wastewater, transportation and logistics, communications and information technology, government operation and other community-based essential function, critical manufacturing, financial services, chemical and hazardous material, defense industiral base, industrial, commercial, residential, and sheltering facility and services.
Low-risk, asymptomatic people
Bach Diagnostic’s COVID-19 PCR test has been authorized by FDA under an Emergency Use Authorization (EUA), and has been authorized only for the detection of nucleic acid from SARS-CoV-2, not for any other viruses or pathogens. The test is only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostic tests for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.
Bach Diagnostic's is providing serology testing based on IgG and IgM. Such tests have either received an emergency use authorization (EUA) from the U.S. Food and Drug Administration (FDA) or were released for use under FDA guidance, “Policy for Diagnostic Tests for Coronavirus Disease-2019 during the Public Health Emergency - Immediately in Effect Guidance for Clinical Laboratories, Commercial Manufacturers and Food and Drug Administration Staff” that was updated on May 4, 2020. Tests being performed under an EUA have not been FDA cleared or approved and LabCorp has completed independent validation of these tests. In addition, various manufacturers have submitted or will seek EUA for their tests
1. Weaver, C. Questions About Accuracy of Coronavirus Tests Sow Worry. The Wall Street Journal. April 2nd, 2020. Retrieved from https://www.wsj.com/articles/questions-about-accuracy-of-coronavirus-tests-sow-worry-11585836001
2. Li R, Pei S, Chen B, Song Y, Zhang T, Yang W, Shaman J2. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science. 2020 Mar 16. pii: eabb3221.
3. Lauer, S. et al., 2020. The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application. Annals of Internal Medicine.
4. National Health Commission of the People’s Republic of China, New Coronavirus Pneumonia Diagnosis and Treatment Program (Trial Version 7).
5. To KK, Tsang OT, Leung WS, Tam AR, Wu TC, Lung DC et al. (2020). Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study. Lancet Infect Dis. 2020 Mar 23. pii: S1473-3099(20)30196-1.