Covid-19 - “Test-test-test” confusion
Wim Van Damme
Tedros, DG of WHO, has repeated frequently the mantra “test-test-test”.
But, in a country such as DRC, this raises many questions, such as:
(1) Testing for which objective? To prevent spread, be it in the country, in a workplace, in a plane? To identify covid-19 cases? To understand where the virus is spreading (regions, hotspots, …)
(2) Testing whom?
o Testing the sick?
o Testing the worried?
o Testing contacts?
o Testing before resuming work?
o Testing before travelling?
o Testing arriving travellers?
o Testing to decide till when a contact or a patient should remain in isolation?
o Testing to know where the virus has spread?
o Testing all patients to protect health care workers from professional exposure?
o Testing health care workers to prevent them spreading the virus to non-covid patients?
(3) Testing with which test? Considering the tests available, and knowing the limits of testing capacity?
(4) How to interpret the test results? (which may arrive with considerably delays; and what to do in the meantime?)
(5) How often to repeat the tests?
And then there are also issues, such as:
- Validation of the different tests in the context (may vary with endemicity of malaria and other infections); which may result in different predictive value depending on contexts;
- What and who to give priority, if capacity is limited (as it almost invariably is);
- What about the costs of all this?
- How far to decentralise testing? Which tests?
- How to assure quality of testing, including of sampling, transport & processing?
With testing capacity being limited quasi-universally and with existing tests having serious limitations, be they PCR, Ag test or Ab test, I am wondering what should be prioritised?
A few considerations:
- For case management, in the absence of a very effective treatment, it is in fact not very important to know whether a patient has covid-19 or another respiratory infection.
- Given the limits of any test, health care workers and non-covid patients risk infection, even from patients who have not been tested, or who have a negative test.
- To assure that someone is not infected and/or non-infectious; she should be tested very frequently.
- …
What is the best strategy to use limited testing capacity?
How can a “rationing strategy” be made acceptable, even to “powerful stakeholders” (be they VIPs, employers, international organisations, international travellers, …)?
Robert Colebunders
Testing is very useful if quarantine and contact tracing is possible
Robert (Bob) Colebunders
International citizen project COVID-19 (ICPCovid)
NSETHIO project
Campus drie Eiken
Gouverneur Kinsbergen Centrum
Doornstraat 331, 2610 Wilrijk
Skype name Robert colebunders
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Stefan Swartling Peterson
Kalk, Andreas GIZ CD
To my best knowledge, antigen tests are mainly positive during the late incubation and the early disease period. Furthermore, the antigen can be detected sometimes (e. g. the famous ‘second’ infections in S Korea) without real infectiousness being given. To my best knowledge again, it is even doubtful in how far viruses remaining on surfaces remain infectious. Hence, I believe that antigen tests are much more meaningful for individual diagnostics than for contact and pathway tracing, i. e. for public health purposes.
On the other hand, antibody testing deepens our understanding of the real spread of the – mostly not very virulent – infection. Figures depicting a high seroprevalence like in Ischgl in Austria (42 % of the entire population), in Heinsberg in Germany (14 %), Geneva (10 %) and on the aircraft carrier Charles de Gaulle (50 %) speak for themselves.
Finally, I allow myself to share three ‘theses papers’ with you. Unfortunately, they are only available in German language by now, but I find them that excellent that I presume they might at least be interesting for Dutch, Flemish and other German-speaking readers.
Dr Andreas Kalk MS (Gen Surg) MCommH
Directeur Résident
Bureau GIZ à Kinshasa
(Rep. Dém. du Congo, Rép. du Congo)
7, av. Comité Urbain
B. P. 7555, Gombe, Kinshasa
République Démocratique du Congo
Tel. : +243-810 844 577
GSM : +243-811 600 455
GSM Allemagne/Germany : +49-151-7189 0706 Nouveau numéro ! New number !
Skype : andreas-kalk
E-Mail : andrea...@giz.de
Internet : www.giz.de
De : covid...@googlegroups.com <covid...@googlegroups.com>
De la part de Stefan Swartling Peterson
Envoyé : lundi 29 juin 2020 18:52
À : Covid-19 in SSA <covid...@googlegroups.com>
Objet : Re: Covid-19 - “Test-test-test” confusion
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Deutsche Gesellschaft fuer Internationale Zusammenarbeit (GIZ) GmbH;
Sitz der Gesellschaft Bonn und Eschborn/Registered offices Bonn and Eschborn, Germany;
Registergericht/Registered at Amtsgericht Bonn, Germany; Eintragungs-Nr./Registration no. HRB 18384 und/and Amtsgericht Frankfurt am Main, Germany; Eintragungs-Nr./Registration no. HRB 12394;
USt-IdNr./VAT ID no. DE 113891176;
Vorsitzender des Aufsichtsrats/Chairman of the Supervisory Board: Martin Jaeger, Staatssekretaer/State Secretary;
Vorstand/Management Board: Tanja Goenner (Vorstandssprecherin/Chair of the Management Board), Thorsten Schaefer-Guembel
Claudia Hanson
Dear Andreas,
You need the PCR for contract tracing, and restriction of movement of contacts (quarantining might take different faces in different settings…). For me this is a crucial preventive public health measures together with distancing, face mask, etc. and together with efforts to mitigate the effect of non-use of health services / encourage health care seeking. As I follow the German news regularly, I see in this also a high educating effects: the public learns about risks situation: you create a knowledgeable community, which is for me key in the marathon we have ahead of us.
But if contact tracing is not possible, than the testing has limited relevance. – But still the community education effect should be considered.
PCR also have their place in the diagnosis, but here again, if no consequences, then….
For classical surveillance I can rather see antibody tests in blood donors or pregnant women, as with HIV, but that is only useful in places where we expect at least some 5% of prevalence (thus not in Africa at present, but in Sweden it has shown to be useful to see the developments). Up to this point, surveillance needs to be PCR based in those who feel ill, contacts, and within influenza surveillance sentinel surveys (as an alert function).
Antibody test, as you say deepen our understanding, clearly and no doubt. But I understand, the immunological response is not yet clear, and antibody test may underestimate – but on the other hand maybe without antibodies no immunity – but everyday new insights….’
I agree that the test, test, test slogan needs to go into more details, but also more details are available, but not that easy to break them down to specific settings…,
Best wishes
Claudia
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Ir Por
The answers to these many questions related to Covid 19 testing are depending on many factors, including the country socio-economic and health system context (capacity and resources to perform the tests) and the status of the epidemic in the country – no confirmed case yet, only imported cases, cluster of cases and spread community transmission. In a country where there is only imported cases, maximizing the tests with accompanied quarantine measures among those coming from abroad is key to prevent further transmission.
For the choice of tests, it is clear that PCR and antigen tests help detect current infection while serological test is for past infection, and each has its advantages and disadvantages.
Por Ir, MD, MPH, PhD
Deputy Director
National Institute of Public Health
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Guido Vanham
Hi Andreas and all,
To avoid confusion, not so clear to me whether you refer to antigen tests (“rapid tests”, detected by ARS-CoV-2 specific antibodies) or PCR (which also detects the “viral antigen” in the broader sense of the word. Both types of test indeed are not designed to detect infectious virus and, outside of lab experiments, it is difficult to prove or disprove whether a “PCR” or “antigen” positive sample contains infectious virus, because, in general, it is not so easy to cultivate virus from “dirty” biological fluids like throat swabs or stools. In addition, for any virus, the infectious viral particles are a minority amongst a lot of incomplete or mutated genomic material, which gives positive signals in PCR (and less so in rapid antigen tests).
But, in general, if you look carefully in “ideal circumstances” you will find a very good correlation between PCR or antigen positivity and infectious titers, with the real antigen (rapid test) being less sensitive than PCR.
Your point about the difference between (high) seroprevalence and (low) frequency of positive PCR or antigen tests in populations, indeed shows that the virus is most probably less virulent or pathogenic than we had the impression in a hospital setting. It is likely that most infections are either abortive (maybe with low dose or less infectious variants) or asymptomatic (low dose?). But that applies to most infectious diseases, doesn’t it? HIV and EBOLA are some of the few exceptions.
Nevertheless, I wouldn’t “downplay” the pathogenicity of this virus too much. At my 66th birthday soon, I would not like to encounter it in an infectious form….. We just Stopped in the small “village fleuri” Larzicourt (just two dozen of houses) where a poster at to the door of the church asked to pray for the corona victims: 18 people, 2/3 male, 2/3 in their eighties with a range from 65 to 101…..
Best wishes from Burgundy
Guido Vanham
From: covid...@googlegroups.com <covid...@googlegroups.com>
On Behalf Of Kalk, Andreas GIZ CD
Sent: dinsdag 30 juni 2020 7:54
To: Stefan Swartling Peterson <stefan.swart...@gmail.com>; Covid-19 in SSA <covid...@googlegroups.com>
Subject: RE: Covid-19 - “Test-test-test” confusion
To my best knowledge, antigen tests are mainly positive during the late incubation and the early disease period. Furthermore, the antigen can be detected sometimes (e. g. the famous ‘second’ infections in S Korea) without real infectiousness being given. To my best knowledge again, it is even doubtful in how far viruses remaining on surfaces remain infectious. Hence, I believe that antigen tests are much more meaningful for individual diagnostics than for contact and pathway tracing, i. e. for public health purposes.
To view this discussion on the web visit https://groups.google.com/d/msgid/covid19SSA/ff0cce3882d344a6ac449d8d9439d317%40giz.de.
Patricia Granja
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Quito-Ecuador
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Claudia Hanson
Dear Patricia,
That is also my thinking: why not going back to what is taught in text books: an improved clinical case definition is what you set up early, artificial intelligence should help us to get this better than just flu symptoms. That would help spoiling less resources in LMIC. The data from Rafaela from Rwanda are an eye opener. And sure, the antibody tests do not help for containing the epidemic anyhow.
Best wishes
Claudia
From: covid...@googlegroups.com <covid...@googlegroups.com>
On Behalf Of Patricia Granja
Sent: Monday, July 6, 2020 3:57 AM
To: Robert Colebunders <robert.co...@uantwerpen.be>
Cc: Wim Van Damme <wvd...@itg.be>; Covid-19 in SSA <covid...@googlegroups.com>
Subject: Re: Covid-19 - “Test-test-test” confusion
Identify, identify, identify (better if we have RT-PCR if not, you should use clinic parameters)
When we forgot to use epidemiology (specially communitarian epidemiology), signs and symptoms?
A person with olfactory loss in a city with raising cases, should be treated as covid positive (and then isolate, compulsory use of face mask, contact tracing etc) even with a negative PCR (in case that is lucky enough to have access to a PCR and even though the result will arrive in 48h hours in an ideal context, so you can lose precious time!!)
Identify (epidemiology= pretest + signs and symptoms)
isolate
contact tracing
treat symptoms
doing a lot of tests without isolating and contact tracing is useless (to much effort and resources on test and no contact tracing and food to support isolation, face masks..)
Be careful about rapid-tests!!
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Robert Colebunders
Indeed use a clinical case definition is very useful
Robert (Bob) Colebunders
International citizen project COVID-19 (ICPCovid)
NSETHIO project
Campus drie Eiken
Gouverneur Kinsbergen Centrum
Doornstraat 331, 2610 Wilrijk
Skype name Robert colebunders
From: Claudia Hanson <claudia...@ki.se>
Sent: maandag 6 juli 2020 7:37
To: Patricia Granja <patrici...@paliativosecuador.org>; Robert Colebunders <robert.co...@uantwerpen.be>
Cc: Wim Van Damme <wvd...@itg.be>; Covid-19 in SSA <covid...@googlegroups.com>
Subject: RE: Covid-19 - “Test-test-test” confusion
Dear Patricia,
Steven Van Den Broucke
- They will be cheap. Estimates are that they would cost between 1 and 5 dollars. That’s around the price of a cup of coffee.
- They can be done on saliva. No brain biopsy required (referring to patients experiencing a nasopharyngeal swab as a pituitary biopsy)
- They can be done frequently. Every day for college students, or healthcare workers, or bus drivers? Every third day for everyone?
- They will answer the key question — am I contagious to others right now?
Finally, and most importantly, they will answer this last question quickly. Results back in less than an hour.
To view this discussion on the web visit https://groups.google.com/d/msgid/covid19SSA/05e4aae120cd4ee79b2d03bc3b7fd43f%40uantwerpen.be.
Patricia Granja
borg...@gmail.com
Dear all,
A colleague of mine working in several elderly homes pointed out the additional difficulties of using anosmia and ageusia for this vulnerable population. When testing a clinical definition (a necessary tool for LMIC) it is imperative to test the usefulness amongst elderly as well.
Rgds
Stefaan Van der Borght
Van: covid...@googlegroups.com <covid...@googlegroups.com> Namens Robert Colebunders
Verzonden: maandag 6 juli 2020 7:51
Aan: Claudia Hanson <claudia...@ki.se>; Patricia Granja <patrici...@paliativosecuador.org>
CC: Wim Van Damme <wvd...@itg.be>; Covid-19 in SSA <covid...@googlegroups.com>
Onderwerp: RE: Covid-19 - “Test-test-test” confusion
Indeed use a clinical case definition is very useful
Robert (Bob) Colebunders
International citizen project COVID-19 (ICPCovid)
NSETHIO project
To view this discussion on the web visit https://groups.google.com/d/msgid/covid19SSA/05e4aae120cd4ee79b2d03bc3b7fd43f%40uantwerpen.be.
Thetard, Rudi
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