Image credits: Dr. Beth Ripley and Timothy Prestero.

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COVID-19 Supply Chain Response: Swab Design and Testing Protocol

Curated by NIH/NIAID in collaboration with the U.S. Food and Drug Administration, the Veterans Healthcare Administration, and America Makes

Nasal swabs, particularly nasopharyngeal (NP) swabs, are an important part of the diagnostic testing procedures for the SARS-CoV-2 virus that causes the current pandemic COVID-19 disease. The expanded demand for testing has increased the need for swabs, and 3D printing technology has emerged as a method to meet the demand. There are a variety of 3D-printed swabs currently available, with different designs and printing methods. The Veterans Health Administration (VHA) is evaluating the safety and functionality of a variety of 3D-printable NP swab designs for use in acquiring samples for COVID-19 diagnostic tests.

Testing protocols can be downloaded from links in the table below. Click here to download a PDF of test results, up to date as of August 17, 2020. All swabs were purchased independently by the VHA. At present, only commercially-available swabs have been tested.

  • Nasal swab manufacturers, including those using 3D printing or additive manufucturing methods, should meet FDA requirements for product labeling, and swabs should be produced in a facility registered and listed with the FDA as meeting requirements for current Good Manufacturing Practices.
  • Per 21 CFR 880.6025, general use nasal swabs (including NP swabs) are Class I devices exempt from FDA pre-market notification. As such, they are not cleared or approved by FDA and should not be labeled as such. For additional information about regulatory or FDA guidance-related questions, please refer to FDA guidance documents, or contact the FDA at deviceshortages@fda.hhs.gov. All other inquiries may be submitted here

Design and Testing Considerations

The areas for risk are as follows and designated for each requirement in the table below. Unless otherwise specified, all the swabs were designed for nasopharyngeal specimen collection.

  • Diagnostic (Dx) Test Compatibility: Nasal swabs are meant to be used as part of a testing kit. 3D printed nasal swabs need to be compatible with the transport tubes, viral transport media and rtPCR testing protocol to ensure an accurate result.
  • Mechanical Testing: Nasal swabs need to be strong enough to not break in use, flexible enough to reach the sample site, but not so flexible that they will buckle when inserted into the nasal passage. Mechanical tests are designed to address these design requirements. See custom devices for nasal swab testing.
  • Patient Safety: Swabs need to be safe for patient use. This covers potential injuries such as nose bleeding (epistaxis), potential foreign body (from a broken swab during use), as well as more global injuries that can occur from an incorrect COVID-19 diagnosis (positive or negative).
= Risk area is relevant to the requirement. = Risk area is not primarily applicable.
Swab Requirements Dx Test
Compatibility
Mechanical
Failure
Patient
Injury
Potential Harm Testing Protocol
Must be sterilizable Unsterile swabs may introduce infection to the patient and may invalidate the test result 3rd Party Report of Sterilization Validation
Must be able to fit through the nasal cavity and reach the sampling location (e.g. nasopharynx, mid-turbinate region) Inability to complete test; lost patient and staff time Go/ No-Go Gauge

Dimensional Analysis
Sterilized swab should not substantially increase the risk of epistaxis (nose bleeds) as compared to the SOC* Usually self-limited; in some cases, can lead to excessive blood loss and need for medical intervention Abrasion Protocol

Indentation Protocol
Sterilized swabs should not break while in the nasal cavity Swab material retained in patient (e.g., nasal cavity) and/or mucosal injury, necessitating additional diagnostic testing and/ or procedures Go/ No-Go Gauge

Fatigue Bending Protocol
Sterilized swab must collect and release a sufficient amount of SARS-CoV-2 sample to render a valid test result (benchmarked to standard of care) Inaccurate test result, improper patient care delivered as a result Adsorption Protocol

Elution Protocol
Sterilized swab must be compatible with (e.g., fit within) the transportation tube Additional burden on testing staff (e.g., needing to cut a swab that is too long) Dimensional Analysis Report

Breakpoint Function Test
Sterilized swab material must not interfere with the PCR test results False negative test result, improper patient care delivered as a result PCR Interference Protocol
Sterilized swab material must be proven safe for mucus membrane contact Mucus membrane irritation, adverse tissue reaction, patient illness Material Biocompatibility Analysis report (ISO 10993)

DEFINITIONS: SOC = Standard of Care; SARS-CoV-2 = the virus that causes COVID-19; PCR = Polymerase Chain Reaction, a step in the diagnostic test for COVID-19 that amplifies the viral genomic material of SARS-CoV-2, to indicate if the virus is present in the patient.


Swab Testing Devices

To support mechanical testing of 3D-printable nasopharyngeal swabs, the VHA designed custom devices. There are a total of 9 protocols that cover testing of 3D-printed swab design requirements. Protocols that require creation of fixtures or jigs are listed here.