Serology plays an important complementary role in the diagnosis and control of covid 19 infection

1. Role of serology in diagnosis & control
of
Covid-19 infection
Prof. Ashok Rattan,
MD, MAMS,
Common Wealth Fellow, INSA DFG Fellow, SEARO Temporary Advisor,
WHO Lab Director (CAREC/PAHO)
Advisor: Pathkind Labs Knowledge Forum, R & D and Quality

2. SARS CoV 2 & Covid 19
• A novel corona virus with tremendous Human to Human transmission
• No previous exposure to it, so everyone is susceptible
• No known effective preventive or therapeutic drug
• Pandemic spreading widely
• Diagnosis playing an important role
• RT PCR : slow, gold standard for diagnosis
• Rapid Antigen test: Rapid but not very sensitive (False Negative)
• So Prescription for containment
• Test, Trace & Treat (Isolate) is the Matra for control
• But Not working effectively in halting spread

3. 3,526, 411
246,482
18 %
12,180,152
552,380
7
Covid 19 Cases
World india
15,656,884 1,288,130
Total Deaths
636, 576 30,645
Total Recovered
9,544,766 817,563
Active Cases
Mild Serious Mild Serious
5,409,354 66,188 430,848 8,944
Cases / million population
2009 933

5. Why SARS CoV 2 is spreading while
SARS was contained
• In 2003 when SARS first appeared, in six months it caused 8100 infections
in restricted geographies: Hong Kong, Singapore & Toronto
• What worked was institution of
• 1. symptom based case detection
• 2. Subsequent testing to guide isolation & quarantine
• SARS CoV 2 has many similarities
• High genetic relatedness to SARS
• Transmissible primary through respiratory droplets
• Frequent lower respiratory symptoms: cough, fever, shortness of breath
• Median IP of 5 days
• But, SARS CoV 2 is different & similar control efforts have not succeeded
• SARS CoV 2 is shed even before symptoms appear
• 80% of infectious persons (shedding virus) are asymptomatic or presymptomatic

7. Antigen detection

8. SARS CoV 2

11. Zhao J et al: Antibody responses to SARS-CoV-2 in patients of
novel coronavirus disease 2019

13. Characteristics Asymptomatic Symptomatic
Number 37 (20.8%) 141 (79.2%)
Median days of viral shedding 19 days
Shortest 6 days
Longest 45 days
14 days (37 sample group)
Ct vales orf 1ab
N
32.8
32.6
31.7
33.5
Virus specific IgG
(3 – 4 wks after exposure) level
30/ 37
Median S/CO 3.4
31/ 37
Median S/CO 20.5
Virus specific IgM 23/ 37 29/ 37
After 8 wks of discharge
IgG levels declined in 28/30 30/31
Median decrease 71.1% 76.2%
Decrease in neutralizing Ab 30/ 37 23 / 37
Percentage decrease 8.3 11.7
Became seronegative 12/ 30 4/ 31

15. Contribution of transmissibility &
severity on population impacted
SARS CoV 2

16. Time lines of Biomarkers
RT PCR
Serology
Antigen
Threshold of
detection

17. • The longitudinal tracking of re-exposure after the disappeared symptoms of the
SARS-CoV-2-infected monkeys :
• weight loss in some monkeys, viral replication mainly in nose, pharynx, lung and
gut, as well as moderate interstitial pneumonia at 7 days post-infection (dpi) were
clearly observed in rhesus monkeys after the primary infection.
• After the symptoms were alleviated and the specific antibody tested positively,
• half of infected monkeys were re-challenged with the same strain
• Neither viral loads in nasopharyngeal and anal swabs along timeline nor viral
replication in all primary tissue compartments at 5 days post-reinfection (dpr) was
found in re-exposed monkeys.
• Monkeys with re-exposure showed no recurrence of COVID-19, similarly to the
infected monkey without re-challenge.
Bao et al: Beijing Key Laboratory for Animal Models of Emerging and Remerging Infectious Diseases

19. Test Type Time to Result
TAT
What it will
tell
What it can
not tell
Expertise
needed
Rapid Card
test
10 to 30 min Presence of
antibodies
yes / no
*Quantity of
antibodies
*Are they
protective
POCT Minimal
Not recommended
by ICMR
ELISA
CLIA
2 to 5 hours Quantitative
test, tire of
antibodies
*Are they
protective or
not
Lab space
Technical skills
Instrument
Plaque
Reduction
Neutralizing
Test (PRNT)
2 to 5 days Presence of
protective
antibodies that
can inhibit the
virus
*May miss
antibodies which
are against
structural
proteins not
involved with
virulence
Lab space
BSL 3 facilities
Technical skill
Live virus
Funds
Time
Interest
Not advised by ICMR

20. Data From
USA FDA
Website
Abbott
Architect
Roche
Elecsys
DiaSorin
Liaison
Euro-
immune
Ortho
Antibody
detected
IgG Pan Ig IgG IgG IgG
Target Nucleocapsid Nucleocapsid Spike Spike Spike
Method CMIA ECLIA CLIA ELISA CLIA
Sensitivity 100 100 97.6 90 90
Specificity 99.6 99.8 99.3 100 100
PPV at 5%
prevalence
92.9 96.5 88 100 100
NPV at 5%
prevalence
100 100 99.9 99.5 99.5
Informs about exposure to SARS CoV 2 presence of protective antibodies to SARS CoV 2

21. Antigen
target
Antigen
target
Exposure Surveillance Acute
infection
Recovered
infection
Immunity Vaccine
assessment
IgG S1, RBD + + - ++ ++ ++
IgG NC ++ ++ - + + +
Pan S1 + + - + + +
Pan NC +++ +++ - + + +
Important attributes of available Serology Tests
Protective Antibodies (neutralizing)
EXPOSED

22. • Orthogonal Testing Strategy
• Sample (serum) should be collected after atleast
two weeks of positive RT PCR result or symptoms
or exposure to a positive case
• First test: 100% sensitive
• Total antibodies against Nucleocapsid (NC)
protein (most immunogenic antigen of the virus)
• If Positive, person has exposure to SARS CoV 2
Reflex to:
• Test against Spike protein
• If positive, person has definitive exposure to
SARS CoV 2 and has had either symptomatic or
asymptomatic Covid 19 infection in the past.
• anti Spike IgG are neutralizing antibodies in
nature and offer protection against infection &
reinfection in animals since viral spike binds to
ACE 2 receptors on human cells to gain entry.
• Not for diagnosis of Acute Covid 19 infection
ECLIA Pan Ig
CMIA IgG

23. Clinical And Analytical Performance Of An Automated
Serological Test That Identifies S1/S2 Neutralizing IgG In
Covid-19 Patients Semi-quantitatively.

24. • In January 2020 : Lab performing Covid 19 RT PCR = 1 (NIV, Pune)
• On 24th June 2020:
• Public labs : 730
• RT PCR : 557
• TrueNat : 363
• Cepheid : 80
• Private labs : 270

25. • Test after two weeks (not useful for detecting acute infection)
• Use IgG based ELISA & CLIA
• Who can test ?
• Government & private hospitals
• Offices
• Public sector units etc
• Share the comprehensive report of antibody testing with ICMR
IgG antibody test

26. • Immunocompromised patients
• Individuals in containment zones
• Health care workers
• Security personnel
• Police & paramilitary personnel
• Press
• Rural, tribals after reverse
migration
• Industrial workers or labour force
• Farmers, vendors visiting large markets
• Staff in municipal bodies
• Drivers
• Banks, post, couriers, telecom offices
• Shops
• Air travel related staff
• International operations
• Congregate settings
• prisons
Who can be tested ?

27. Surveillance (Spread of Infection)

28. Thyrocare Serosurveillance results after > 50,000 tests
Pin Place %
110009 New Delhi 33.3
120001 Gurgaon 20.8
123501 Mehendergarh 1.9
201301 Gautam Budh 23.7
380060 Ahmedabad 18.9
395006 Surat 21.6
400009 Mumbai 35.6
400097 25.7
400705 Navi Mumbai 28.1
401302 Thane 47.1
411046 Pune 19.9
560002 Hyderabad 37.3
560057 Bangalore 44.1
600034 Chennai 27.3
700020 Kolkotta 21.7
800014 Patna 19.6
842001 Muzzafarpur 13.8
800105 Katihar 8.7
> 40%
20%
20%
<
20%
30%
Covid 19 antibodies present

30. Should antibody test be performed before surgery ?

31. Convalescent Plasma Therapy
• Can convalescent Plasma therapy from recovered
coronavirus patient treat infected people?
• Yes, is there are neutralizing antibodies present, we will
know only if we can test for antibodies in patients

32. Can I go back to work ?
• If a person has antibodies to SARS CoV 2, tested 14 days after symptoms or
contact with a positive patient, it means
• Persons had been infected
• If person has neutralizing antibodies, he is protected
• Can go back to work
• Personal protection & social distancing would still be useful

33. When used as a complementary test with RT PCR
Serology can function as a reliable diagnostic aid indication
recent or prior infection

34. Guo L et al: Profiling Early Humoral Response to Diagnose Novel Coronavirus Disease (COVID-19) CID 2020
RT PCR RT PCR + Serology

35. Test What it detects Sample Time for test Expect
report in
Sensitivity
(True positive)
Specificity
(True Negative)
RT PCR
(Gold standard)
Viral RNA
increased many
fold over original
level
(106 fold increase)
Respiratory
NP, TS,NS
4 to 6 hrs 24 hours 80 – 90%
time dependent
90 - 100
CBNAAT or
TRUE NAT
“
closed system
“ 90 min 4 hours “ “
Rapid
Antigen
Protein fragments
of SARS CoV2 virus
At original level
“ 30 min 60 min 40% “
Pan Ig to NCP Antibodies to viral
Nucleoprotein
Blood
(serum)
60 min 4 hours > 95% >95%
IgG to S1/S2
Spike
Protective
antibodies
“ 60 min 4 hours >90 % >90 %

38. SARS CoV 2 Detection in Covid 19 Infection is a moving target, the current
presentation is based on available information,
recommendations may change depending upon availability of better scientific data