Covid 19 laboratory diagnosis.

1. Laboratory Diagnostics
of Covid-19
Laboratory Diagnostics
of Covid-19

2. Other
tools
& clinical
diagnosis

3. Waiting for vaccine or drugs……………

4. Overview
Identifying persons infected with SARS–CoV-2 infection is central to control the
global pandemic of COVID-19.
The use of diagnostic testing on a massive scale has been a cornerstone of
successful containment strategies.
Real-time reverse transcriptase polymerase chain reaction–based assays
performed in a laboratory on respiratory specimens are the reference standard
for COVID-19 diagnostics.
However, point-of-care technologies and serologic immunoassays are rapidly
emerging.

5. Overview (Cont.,)
Laboratory diagnosis of symptomatic patients is effective, when coupled
with patient history and clinical data.
Important gaps remain in:
• Screening asymptomatic persons in the incubation phase,
• Accurate determination of live viral shedding during convalescence to
inform decisions to end isolation.
• Challenges encountered in test delivery and specimen collection that have
inhibited rapid increases in testing capacity.
These challenges may be even greater in low-resource settings.

6. 1. The test detects infection directly (such as the virus itself) or indirectly
(such as host antibodies),
2. Test turnaround time.
3. The ability to perform many tests at the same time.
4. The need to have a minimum number of specimens before testing.
5. The ability to perform the test in low-infrastructure settings.
6. The potential for use at the point of care depends on test complexity.
Tests considerations

7. 1. Waived tests are available for use at the point of
care.
2.Moderate- and high-complexity tests must be
performed in a laboratory.
The U.S. Food and Drug Administration (FDA) categorizes diagnostic
tests by their complexity:
Labelled RUO (research use only)

8. https://www.nature.com/articles/d41586-020-01221-
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C01_GL_Nature&fbclid=IwAR2BE5STcGC45xvYu_RYUogqp3yluN79HAhQqar0P2Umqsguw0tAuoS0hgA

9. Electron Microscope
isothermal amplification

10. CRISPERCAS12
CRISPR–Cas12-based assay for detection of SARS-CoV-2.

11. Why testing?
1

12. Why and where testing is needed
Active and/Passive Surveillance
Monitoring contacts/ Contact tracing
Incubation period Symptoms Convalescence
Screening of asymptomatic patients Screening of symptomatic patients
Diagnosis Treatment initiation decision
Monitoring of viral shedding
Discharge/termination of Isolation

13. Who to Test?
In most countries, diagnostic testing indications and capacity were
limited at the beginning of the outbreak
To expand access to testing, the FDA released policies to allow
laboratories to use their validated assays in a more timely manner.
On 4 March, the Centers for Disease Control and Prevention (CDC)
removed restrictive testing criteria, recommending that clinicians
use their judgment to determine whether a test should be
performed.

14. Who to Test?
The CDC still recommends priority for testing 3 groups:
1. Hospitalized patients with presentations compatible with
COVID-19.
2. Other symptomatic persons at risk for poor outcomes
3. Persons who had close contact with someone with suspected
or confirmed COVID-19 within 14 days of illness onset or have
a history of travel in an affected area

15. How to Test?
• Among patients diagnosed with COVID-19, the occurrence of concomitant
viral infections has been reported to range from below 6% to greater than
60% .
• As a result, it is not possible to rule out SARS–CoV-2 infection merely by
detecting another respiratory pathogen.
• Real-time reverse transcriptase polymerase chain reaction (RT-PCR)–
based assays performed in the laboratory on respiratory specimens are
the cornerstone of COVID-19 diagnostic testing.
• Several novel or complementary diagnostic methods are being developed
and evaluated
Diagnostic Tests in Use or Under Evaluation

16. Laboratory tests
✓ Reference standard
Laboratory based rt-PCR01
✓ Point of Care test
Sample to answer NAAT
assays
02
✓ Under development
Antigen Detection03
✓ Laboratory based
✓ Point of care
Serology IgM & IgG04

17. POC
Point
of care

18. InterpretingDiagnosticTestsforSARS-CoV-2
NandiniSethuraman,MD1;Sundararaj
StanleyrajJeremiah,MD2;AkihideRyo,MD,PhD2
IgG
BAL
PCR
Stool
PCRNP
PCR
Virus
isolation
IgM

20. PCR Vs. Serology

21. COVID-19
Diagnostics/Specimens

22. Specimens
Since COVID-19 is an infectious respiratory tract infection, respiratory material
should be collected, at a minimum:
1.upper respiratory specimens: nasopharyngeal and oropharyngeal swabs or
wash in patients still capable of movement.
2.lower respiratory specimens: sputum (if produced) or endotracheal aspirate
or bronchoalveolar lavage in patients with more severe respiratory disease.
•Additional clinical specimens can be collected as the COVID-19 virus has been
detected in blood and stool.
•In the case of deceased patients, the collection of autopsy material including
lung tissue should be considered.
•In recovered patients, paired serum (acute and convalescent) can be favorable
to define cases as serological assays become available retrospectively.

23. Specimens
Saliva samples preferable to deep nasal swabs
for testing COVID-19
Taken together, our findings demonstrate that saliva is a viable
and more sensitive alternative to nasopharyngeal swabs and
could enable at-home self-administered sample collection for
accurate large-scale SARS-CoV-2 testing.
https://www.medrxiv.org/content/10.1101/2020.04.16.20067835v1.full.pdf

24. Safety issues
Clinical laboratories performing routine haematology,
urinalysis, and clinical chemistry studies, as well as
microbiology laboratories performing diagnostic tests on
serum, blood, or urine specimens should follow standard
laboratory practices, including standard precautions,
when handling specimens from potential COVID-19
patients.
Viral RNA detected in serum
Viral RNA detected in Blood
https://www.cdc.gov/coronavirus/2019-ncov/lab/lab-biosafety-guidelines.html

26. COVID-2019 Test
Interpretation Of Result
Positive Result
Negative Resuit
Inconclusive Result

27. • The current pandemic highlighted the vital role of diagnostics in the
control of communicable diseases.
• Laboratory-based molecular assays for detecting SARS–CoV-2 in
respiratory specimens are the current reference standard for COVID-19
diagnosis.
• Point-of-care technologies and serologic immunoassays are rapidly
emerging.
• Early, massive deployment of SARS–CoV-2 diagnostics for case finding
helped controlling the epidemic in several countries.
• There is an unprecedented global effort to increase testing capacity of all
healthcare settings.
Take home messages

28. THANK YOU