Guidance

COVID-19: laboratory investigations and sample requirements for diagnosis

Updated 29 March 2021

Scope

This document describes the samples required for establishing a diagnosis of COVID-19 acute respiratory disease and the tests that will be performed in England.

Initial steps and arranging testing for COVID-19

Please refer to guidance on coronavirus testing, including who is eligible for a test and how to arrange laboratory testing. More information is provided in the specific guidance on safe sampling and handling of laboratory samples and infection prevention and control.

Testing is performed by NHS Trust laboratories, Public Health England (PHE) laboratories, and the UK Lighthouse Labs Network.

Following clinical assessment some patients in healthcare settings may require testing for influenza and other respiratory viruses when these viruses are known to be circulating or are suspected based on exposure and travel history. Additional samples may be required for detection of other viruses, please check requirements with the local laboratory. The influenza surveillance reports can be found at weekly national flu reports: 2019 to 2020 season.

If testing for avian influenza is also indicated (based on assessment of travel and exposure histories), specific and separate samples will need to be collected and sent to the appropriate public health laboratory as per routine practice. For more information, refer to PHE Avian influenza: guidance, data and analysis.

If testing for MERS-CoV is also indicated (based on assessment of travel and exposure histories), specific and separate samples will need to be collected and sent to the relevant public health laboratory.

The local PHE Health Protection Team should be informed where testing is being undertaken in the situations detailed at investigation and initial clinical management of possible cases.

Samples required for initial diagnostic testing

1. Upper respiratory tract sample(s):

• combined nose and throat swab (*) – a single swab used for throat then nose into one pot of viral transport medium. Both palatopharyngeal arches and both nostrils should be swabbed with the single swab. This is also suitable for patients with a tracheostomy and or laryngectomy

• a nose swab is recommended where it is not possible to sample both the nose and throat. Both nostrils should be swabbed with a single swab

• or a nasopharyngeal aspirate in a universal transport pot

(*) Bacterial or charcoal swabs are not suitable

Refer to guidance on how to take swab samples

2. Lower respiratory tract sample (sputum) if obtainable, in universal container

Label each sample with patient ID, date of birth, and date and type of sample and submit to your local testing laboratory according to usual procedures.

Sending samples to the testing laboratory

For hospitals without local testing, the referring laboratory must send the sample to the designated laboratory listed in how to arrange laboratory testing. There is no need to call the health protection team (HPT) or regional laboratory to request testing.

All samples for COVID-19 testing should be packaged and transported in accordance with Category B transportation regulations and labelled ‘Priority 10’. UN 3373 packaging must be used for sample transport.

Further guidance is given on packaging and transport of samples in safe handling and processing for laboratories. PHE follows the World Health Organization (WHO) guidance on regulations for the transport of infectious substances 2019 to 2020.

If the referring laboratory needs to know whether the samples have arrived at the designated laboratory, they should contact the courier for tracking information.