COVID-19 serological testing devices: Notice on sensitivity and specificity values
Published: June 24, 2020
Purpose and background
The purpose of this notice is to communicate target and minimum values of sensitivity and specificity for COVID-19 serological testing devices.
Health Canada has published guidance on requirements for serological antibody tests submitted under the COVID-19 Interim Order (IO). This guidance outlines the requirements that these products must meet. Refer to the authorization of serological testing devices and a list of authorized testing devices for more information.
This document addresses only sensitivity and specificity for serological tests. It complements the published guidance.
Sensitivity and specificity are measures of the diagnostic accuracy of a testFootnote 1 :
- sensitivity is the proportion of subjects with the target condition in whom the test is positive
- specificity is the proportion of subjects without the target condition in whom the test is negative
They are both important measures to determine whether test information is useful and reliable.
Minimum values for sensitivity and specificity
Health Canada does not usually set minimum standards for sensitivity and specificity. Normally we review the submitted data to determine whether a test performs to the standard claimed by the manufacturer. We then compare that to the standard claimed by similar tests.
However, the COVID-19 pandemic is a unique public health crisis. We have received an unprecedented number of applications for serological tests to detect antibodies to SARS-CoV-2. For this reason, we are taking a different approach.
We have set minimum standards for sensitivity and specificity that a COVID-19 serological test must meet in order for us to consider it for authorization. Tests with sensitivity and specificity values below these minimums do not meet the criteria of 5(c) and (d) of the Interim order respecting the importation and sale of medical devices for use in relation to COVID-19, and will not be authorized.
Health Canada considers the following to be unacceptable for authorization:
- sensitivity below 90% for IgG antibodies or total antibodies in samples collected 2 weeks or more after onset of symptoms, or
- specificity below 95%
Sensitivity and specificity values below these values will produce too many false positive or false negative results. These tests will not be authorized, regardless of any other factors.
Tests with sensitivity and specificity values above the minimums will not necessarily be authorized. We consider many factors when making a decision to authorize a testing device. These include:
- whether the device exceeds the target sensitivity value of at least 95% for IgG or total antibodies in samples collected 2 weeks after onset of symptoms
- whether the device exceeds the target specificity value of at least 98%
- whether the sensitivity and specificity values were measured in a substantial number of patients (for example, more than 50 positive samples collected more than 2 weeks after onset of symptoms were used to measure sensitivity)
- whether the tested population represents wide variability (for example, negative samples collected from both healthy patients and patients presenting with infections and respiratory symptoms from causes unrelated to COVID-19)
Testing devices meeting these criteria are better able to demonstrate that they meet the requirements of paragraphs 5(c) and (d) of the Interim Order.
While these factors do not directly lead to authorization or refusal, we use them as guides when considering a test’s performance. The sensitivity and specificity of tests when used in the field may be slightly lower than the values identified through pre-market studies. This is because pre-market studies tend to be conducted under optimal conditions. These additional factors make it more likely that the test will still perform well in a clinical setting.
Health Canada’s target values align well with international targets from other trusted regulators, as set out in the table below. However, as more research results become available, we may revise these values accordingly.
Health Canada welcomes applications for technologies that exceed the minimum limit values. We will consider their performance in relation to the target values when making a decision whether to authorize the device. We will also continue to monitor emerging science and international experience to determine whether we need to amend these values.
International Comparison of Target Values for Sensitivity and Specificity
|UK MHRA||>98% (95% CI 96%-100%) on specimens collected 20 days or more after the first appearance of symptoms||>98% (95% CI 96%-100%)|
|US FDA||90% overall
|95% (overall - total)|
|Health Canada||95% for IgG or total antibodies in samples collected 2 weeks or more after symptom onset.||98%|
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