There are two issues regarding false negatives:
1.
The PCR test: the paper
https://jamanetwork.com/journals/jama/fullarticle/2762997 by Wenling Wang, PhD1; Yanli Xu, MD2; Ruqin Gao, MD3; et al JAMA, March 11, 2020. Detection of SARS-CoV-2 in Different Types of
Clinical Specimens describes PCR detection in different body fluids. Numbers are low, but note the finding that not all nasal swabs are positive and broncheoalveola lavage fluid is better.
2.
The antibody test: As Ian has pointed out in one study
antibodies were detectable with a rise between 7 (IgG) and 9 (IgM) days of symptom onset. Thus potential for false negative due to early testing. My heart sinks when I hear that ambulance drivers are using antibody tests on symptomatic patients when they
go to their houses.
martin
<image002.jpg>
From: Craig Webster [mailto:[log in to unmask]]
Sent: 28 March 2020 16:22
To: Myers Martin (LTHTR); [log in to unmask]
Subject: [EXTERNAL] Re: COVID-19 test performance characteristics
Please note this message has arrived from an external sender.
Be careful when opening attachments or links, especially if logging in or providing data.
If you require assistance, please contact the LTH IT Service Desk.
---------------------------------------------------------------------------------------------------------------
papers I've seen have flipped between using RTPCR as the Gold Standard or CT and or clincal diagnosis. The sensitivity was based around the PCR 'missing' cases possibly tested too early or poor sampling technique.
bw
Craig
Craig Webster
Consultant Clinical Scientist
Acting Pathology Director
Clinical Service Lead - Biochemistry and Immunology
|
Internal:
|
15959
|
|
Mobile:
|
+44 7958 577328
|
|
Email:
|
[log in to unmask]
|
|
Web:
|
http://www.uhb.nhs.uk
|
Office 23 CLS Level -1 UHB
Pathology - University Hospitals Birmingham NHS Foundation Trust
Birmingham, B15 2GW
How is sensitivity being defined here? It is my understanding that it may take 4-6 weeks before antibodies are produced – test early and get a negative!
From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
On Behalf Of Craig Webster
Sent: 27 March 2020 23:29
To: [log in to unmask]
Subject: [EXTERNAL] Re: COVID-19 test performance characteristics
Please note this message has arrived from an external sender.
Be careful when opening attachments or links, especially if logging in or providing data.
If you require assistance, please contact the LTH IT Service Desk.
---------------------------------------------------------------------------------------------------------------
Today, I heard the deputy CMO mentioned the words 'sensitivity' and 'specificity' when answering a question on tests at the 5pm briefing.
Are there any estimates of these parameters for the tests in use?
All the very best to everyone who is at the sharp end of this crisis.
--
------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views
expressed are those of the individual who posts and they are solely responsible for all message content. The ACB does not monitor posts. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/
------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views
expressed are those of the individual who posts and they are solely responsible for all message content. The ACB does not monitor posts. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual who posts and they are solely responsible for all message content. The ACB does not monitor posts.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/