2. Collecting and Handling Specimens Safely
• For healthcare providers collecting specimens or working within 6 feet of patients suspected to be
infected with SARS-CoV-2, use recommended personal protective equipment (PPE), which
includes an N95 (Face Masks) or higher-level respirator, eye protection, gloves, and a gown.
• For diagnostic testing for current SARS-CoV-2 infections, collecting and testing of an upper
respiratory specimen, Nasopharyngeal specimen (NP) collection /Oropharyngeal (OP) (throat)
specimen is recommended.
• Testing lower respiratory tract specimens is also an option. For patients who develop a productive
cough, sputum can be collected and tested for SARS-CoV-2 when available. However, the
induction of sputum is not recommended due to the possibility of aerosol production during the
procedure.
3. Storing and Shipping Respiratory Specimens
• Store respiratory specimens at 2-8°C for up to 72 hours after collection.
• If a delay in testing or shipping is expected, store specimens at -70°C or below.
Store extracted nucleic acid samples at -70°C or lower.
4. PCR: Gold Standard for SARS-CoV-2
Detects presence of SARS-CoV-2 viral nucleic acid, generally during acute phase of
infection.
Result Interpretations:
Positive: Active infection with SARS-CoV-2
Negative: likely not infected when the sample was collected.
5. PCR: Gold Standard for SARS-CoV-2
Limitations
• Sample collection and transport
impact the test accuracy
• Individuals may still test positive by
PCR but not be infectious
• Turnaround time ranges (<1hr to
multiple days).
Benefits
• Most sensitive and specific
• Gold standard to diagnose acute
infections
• Can identify infection in asymptomatic
individuals
6. Antigen tests: Quicker, Cheaper but less sensitive
Detects the presence of SARS-CoV-2 by binding to viral surface proteins (antigens)
.
Results Interpretations:
Positive: Active infection with SARS-CoV-2, person is presumed to be contagious.
Negative: does not rule out infection, may be considered presumptive & confirmed
with a molecular test.
7. Antigen tests: Quicker, Cheaper but less sensitive
Limitations
• No amplification steps: Far less
sensitive (Risk of false negatives).
• Best for symptomatic individuals early
during infection (when viral load is
highest.
• False Positive can occur.
Benefits
• Rapid (~15mins)
• High specificity
• Positive results informs clinical
decisions and infection control
measures.
8. Antibody test: useful to assess exposure, not for
diagnosis
Detects the body’s immune response to SARS-CoV-2 (i.e. past infection,not active
infection)
Takes 2-3 weeks post-infection to develop antibodies (IgM, IgG)
Results Interpretations:
Positive: Previous infection with SARS-CoV-2, Doesnot indicate current infection.
Negative: Probably has not been infected with SARS-CoV-2 or too early in infection
to have detectable antibodies.
9. Antibody test: useful to assess exposure, not for
diagnosis
Limitation
• Risk of false positives
• Should not be used to diagnose active
infection.
• Unknown how long protective
antibodies last (months?)
Benefits
• Determining population-level
exposure, especially when some are
asymptomatic.
• Determine who can donate
plasma/blood as possible treatment for
severely ill.
