Living Evidence - rapid testing

Living evidence tables provide high level summaries of key studies and evidence on a particular topic, and links to sources. They are reviewed regularly and updated as new evidence and information is published.

Quantitative reverse transcription-PCR (RT-qPCR) assay for COVID-19 using upper and lower respiratory tract specimens (nasopharyngeal swab, throat swab and sputum) is considered the gold standard for diagnosing COVID-19.

Rapid point-of-care tests provide results within minutes of the test being administered, allowing for rapid decisions about patient care. It also provides the possibility to extend testing to geographically isolated communities and populations that cannot readily access onsite diagnostic services.

Table one - Test types

  NAAT (RT-PCR) Rapid antigen tests Rapid molecular testsRapid antibody tests

Definition

Detect SARS-CoV-2 viral (Ribonucleic acid) RNA

Identify virus proteins, often using disposable single-use devices

Detect the virus’s genetic material, using small portable or table-top devices

Detect human antibodies produced in the days and weeks after a person is infected

Sensitivity

99.91 - 99.98%

False negative rates that subsequently turn positive cases, in symptomatic patients early in the disease, have been estimated to be as high as 20% to 30%

72% (symptomatic)

58% (asymptomatic)

Results are better early in disease. It is not clear whether all tests pick up the delta variant.

73%* (ID NOW)

100%* (Xpert Xpress)

*Insufficient data to investigate the effect of symptom status or time after symptom onset

The combination of IgG/IgM:

30% (for 1 to 7 days)

72% (for 8 to 14 days)

91% (for 15 to 21 days)

Specificity

97.4 - 99.1%

At times where infections are rare, population prevalence surveys have shown false positive rate of RT‐PCR of less than 0.077%

99.6% (overall summary specificity in symptomatic and asymptomatic patients)

99.7%* (ID NOW)

97.2%* (Xpert Xpress)

*Insufficient data to investigate the effect of symptom status or time after symptom onset

98%

Specimen type

Nasal, Nasopharyngeal, Oropharyngeal, Sputum, Saliva

Mostly Nasal, Nasopharyngeal

Some studies have used oropharyngeal and saliva

Mostly Nasal, Nasopharyngeal

Some studies have used oropharyngeal and saliva, not all instruments TGA registered or validated for saliva.

Blood test (serology)

Time to perform the test

Generally less than 24 hours after the laboratory receives specimen.

Most range from 15 minutes–30 minutes

Approximately 15 minutes (ID NOW)

Approximately 60 minutes (Xpert Xpress)

Time varies depending on assay and device type

Up to two hours

Processing modality

Individual specimen

May use pooled samples depending on disease incidence and samples

Individual specimen

Each rapid antigen test is a single test on a single individual

Individual specimen

This is dependent on what rapid system is used and how it is used

Individual specimen

Applications

Gold standard for diagnosis

Pooled sample testing can be considered for  individuals/where prevalence is low.

For screening, many publications recommend a twostep screening strategy: rapid antigen testing as a first diagnostic method followed by RT-qPCR to distinguish false from true positives.

Repeated mass antigen testing can temporarily reduce the number of new infections. For lasting effects, re-testing at regular intervals would likely be necessary.  The benefits of testing tend to be small in low-prevalence settings.

For screening, many publications recommend a twostep screening strategy: rapid antigen testing as a first diagnostic method followed by RT-qPCR to distinguish false from true positives.

Communicable Disase Network Australia (CDNA) and Public Health Laboratory Network (PHLN) recommends preserving laboratory-based serology tests for where the result will influence individual patient or outbreak management.

In the US, CDC suggest a two-step testing algorithm, in which an initial positive test is confirmed by a second, different antibody assay.

Table two - Test samples

 Saliva Respiratory specimensSerum

Collection method

Different collections methods reported including:

Nasopharyngeal, oropharyngeal and nasal swabs

Fingerpick blood test

Self-collection

The sensitivity of a self-saliva sample was inferior by 9.5% compared to a healthcare work swab. Sensitivities up to 95% reported.

Sensitivity for detecting SARS-CoV-2 in patient collected (compared to professionally collected) tongue, nasal, and mid-turbinate samples was 89.8%, 94.0% and 96.2% respectively.

Sensitivity depends upon the collection methods and device.

High percentage (97-99%) able to self-collect an adequate sample

Sensitivity

85%

97% (nasal and throat swab)

86% (nasal swab)

68% (throat swab)

Specificity depends upon the collection methods and device.

The combination of IgG/IgM:

30% (for 1 to 7 days)

72% (for 8 to 14 days)

91% (for 15 to 21 days)

Specificity

99%

99% (nasal and throat swab)

99% (nasal swab)

97% (throat swab)

98%

Test mechanism

RT-PCR

Isothermal nucleic acid amplification tests e.g. LAMP

Infrared light technology

Lateral flow

Rapid antigen tests

Rapid molecular tests

RT-PCR

Isothermal nucleic acid amplification tests e.g. LAMP

Lateral flow

Rapid antigen tests

Rapid molecular tests

Antibody tests

Lateral flow immunoassay technology

Table three - Policy and evidence

 NSWAustraliaNZUKUSACanadaEvidence

Preadmission hospital/surgery

NSW does not recommend routine COVID-19 testing prior to surgery.

Routine preoperative testing is not recommended in patients with no risk factors.

Routine preoperative testing is not recommended in patients with no risk factors.

Self-test 3 days before the day of procedure.

The CDC recommends pre-procedure or pre-admission testing be at the discretion of the facility.

Recommendations vary by province.

Ontario: In areas with high community transmission, surgery patients who require a general anaesthetic and are not fully vaccinated should be tested 24-48 hours before the procedure. Testing is not required in areas with low community transmission.

Observational studies have found that rapid antigen testing in the emergency department can improve the identification of COVID-19 infected patients and assist with patient management.

Routine testing population

Testing is recommended for anyone who has: COVID-19 symptoms; visited a place at the same time as a  COVID-19 case or have been told they are a close or casual contact.

Anyone with even mild cold or flu-like symptoms should get tested.

The TGA has approved rapid antigen tests for home use.

Anyone who has any COVID-19 symptoms, been at a location of interest at the relevant time, or been identified as a contact should be assessed and/or tested based on symptoms and circumstances.

Anyone who does not have symptoms can perform regular rapid lateral flow self-tests to check for COVID-19.

Anyone with signs or symptoms of COVID-19 should have diagnostic testing.

The CDC also recommends screening tests for unvaccinated people to identify those who are asymptomatic. Examples of screening include: employees in the workplace; students and staff at schools or universities; before or after travel.

Deciding who should be tested is based on symptoms, underlying medical conditions, and risk of exposure to COVID-19.

A systematic review identified six categories of rapid testing initiatives: mass screening; targeted screening; healthcare entry testing; at-home testing; surveillance; and prevalence survey.^

Cochrane review on rapid antigen tests identified virtually no evidence for mass screening of asymptomatic individuals using rapid antigen tests in people with no known exposure, and no evidence of test accuracy in at-risk asymptomatic groups.

Rapid antigen tests have been implemented across a variety of settings including: frontline screening at emergency departments, mass gathering live music eventhospital admissionschoolsscreening test for travellerspoints of entry, targeted testing to release individuals from unnecessary quarantine, and targeted testing in outbreak settings.

The benefits of screening with rapid antigen testing is proportional to disease prevalence, with greater benefit from higher community risk.

A French study found that population testing could have a significant impact on mortality rate.

Routine testing staff

NSW quarantine worker surveillance and testing program with saliva testing.

Mandatory COVID-19 surveillance testing was introduced for workers in local government areas of concern during the current Sydney outbreak.

Rapid antigen test kits were made available to residential aged care, home care, short-term restorative care, and services delivered through the Commonwealth Home Support Program.

Rapid antigen tests will be performed onsite for selected workplaces and schools in NSW.

Regular testing of asymptomatic staff working in COVID-19 quarantine and isolation settings is recommended. Large-scale, non-targeted asymptomatic testing is not currently recommended.

TGA has approved rapid antigen tests for use in Australia.

Regular, mandatory testing for border workforce groups.

Targeted asymptomatic testing of primary health providers only on advice from Ministry of Health and/or public health unit.

Private-sector employers are recommended to offer their on-site staff access to a minimum of two lateral flow tests per week.

Employers that require staff to travel regularly across UK borders must help their staff get tested for COVID-19.

Point-of care testing in residential aged care facilities assists identification of infection in residents and staff.

Testing asymptomatic healthcare workers without known or suspected exposure to SARS-CoV-2 is recommended for workers in nursing homes. Testing asymptomatic healthcare workers who do not work in nursing homes may be considered if resources are available.

No real-world evidence to support or refute routine screening, the potential harms and costs outweigh the benefits for long term care staff.

An Italian observational study found systematic surveillance of asymptomatic vaccinated healthcare workers uncovers more breakthrough infections than symptom-based testing. 
Pre-entry testing for travellers Passengers travelling to Australia must be tested for COVID-19 72 hours or less before scheduled flight departure, and display evidence of a negative test result at the time of check-in. PCR testing is required. Most travellers are required to have a negative pre-departure test result returned within 72 hours of scheduled departure. 

Travellers must take a COVID-19 test within three days of travelling to England, Wales or Scotland if they do not qualify as fully vaccinated or have been in a red list country or territory in the 10 days before arrival.

Travellers who are fully vaccinated and have not been in a red list country do not need to have a test.

All air passengers arriving to the US from a foreign country must have a COVID-19 test no more than 3 days (fully vaccinated) or 1 day (not fully vaccinated) before their flight departs and present the negative result or documentation of having recovered from COVID-19 to the airline before boarding the flight.

All travellers ≥ 5 years, regardless of citizenship or vaccination status, must provide proof of a COVID-19 negative molecular test result or proof of a previous positive test result taken between 14 and 180 days. Rapid antigen tests not accepted.

Background

The Royal College of Pathologists of Australasia highlights that rapid antigen tests have lower sensitivity and specificity and therefore should never be used alone for diagnostic purposes. They may need to be used for surveillance purposes in circumscribed agreed settings in COVID-19 hotspots.

Point-of-care testing may not necessarily be constituted by ‘close to patient’ ‘easy use’ or ‘simple platform’ devices. Rapid output devices are usually cartridge-based tests that can only be run serially on one instrument and take the full onboard run time for analysis. For example, a one-hour test takes one hour for one test after which you can run another one-hour test on another patient.

Lateral flow devices are a form of testing for SARS-CoV-2 which rely on the detection of viral antigens by immunoassays.

Some rapid diagnostic tests may lead to high rates of false negatives and false positives.

Limitations

Different testing protocols are used throughout the literature, as well as differing definitions of what constitutes a rapid test. Some publications did not include in their results how long the test took. Implications of self-collection of tests, including the potential implications to public reporting of cases, are not explored in this review.

The methods for recording or interpreting the results of these tests may be rudimentary and often manual with no electronic repository available for collection or documentation into any patient result record. The expectation that these tests can be done at volume is not necessarily accurate given the manual requirements necessary.

Many studies are product specific and heterogeneous performance may limit our ability to assess the efficacy of the generic approach.

Sensitivity and specificity rates were taken from Cochrane reviews where available, otherwise recent systematic reviews and do not represent a full range as reported throughout the literature. In regards to rapid molecular tests, only tests evaluated in the published Cochrane review are included in this table.

Living evidence tables include some links to low quality sources and an assessment of the original source has not been undertaken. Sources are monitored daily but due to rapidly emerging information, tables may not always reflect the most current evidence. The tables are not peer reviewed, and inclusion does not imply official recommendation nor endorsement of NSW Health.

Last updated on 2 Dec 2021

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