How are specimens collected for coronavirus disease 2019 (COVID-19) diagnostic tests?

Updated: Apr 02, 2021
  • Author: James J Dunn, PhD, D(ABMM), MT(ASCP); more...
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Answer

Answer

Collecting the appropriate specimen at the right time and transporting it to the laboratory under proper conditions are critical pre-analytic components of the testing process. The type of specimen collected will depend to some extent on the authorized SARS-CoV-2 viral test used; the instructions for use (IFU) provided by the manufacturer for FDA Emergency Use Authorization (EUA) will detail the approved sample types. Initial direct viral detection is typically performed using an upper respiratory tract (URT) specimen. Such specimens may include healthcare personnel (HCP)–collected nasopharyngeal (NP), oropharyngeal (OP), mid-turbinate (MT), or anterior nares swabs, as well as NP or nasal wash/aspirate specimens. [3] Swabs should be composed of synthetic fibers and have plastic or wire shafts. Wooden shafts or calcium alginate swabs may contain substances that inhibit some viruses and nucleic acid detection reactions. If both NP and OP swabs are collected, they can be combined in a single tube to maximize test sensitivity and conserve transport devices.

In certain situations, it may be acceptable for patients to collect their own nasal or mid-turbinate swab or saliva (1-5 mL), as long as they are given a clear, step-by-step protocol of the process. [4] Swabs are typically placed in 1.5-3 mL of viral transport media (VTM) prior to transport to the laboratory. In some cases, for point-of-care tests, the manufacturer's IFU may call for direct testing of the swab without dilution in VTM. Collection of lower respiratory tract (LRT) specimens such as sputum, bronchoalveolar lavage (BAL), or tracheal aspirate (in mechanically ventilated patients) may be warranted in certain cases. However, in hospitalized patients with LRT disease, the Infectious Diseases Society of America (IDSA) recommends first obtaining a URT specimen for testing; if it is negative for SARS-CoV-2, an LRT specimen can be collected and tested. [4] HCP collecting specimens and in close patient contact should use recommended personal protective equipment (PPE) and maintain good infection control practices. Other HCP handling specimens after collection should follow standard precautions.

Although at-home sample collection kits for COVID-19 testing have been available by prescription, in December 2020, the LabCorp Pixel COVID-19 Test Home Collection Kit became the first to receive an FDA EUA for nonprescription use. The kit can be purchased by individuals aged 18 years or older, who collect a nasal swab sample at home and send it to be tested at a LabCorp facility. [5, 6]


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