TABLE 1.

Preclinical (phase I) evaluation testing parameters and acceptance criteria

Parameter	Description or comments	Acceptance criteria
Measurements
Total length	Length of NP swab from end to end	15–16 cm
Head length	Length of NP swab head used for collection of secretions and cellular material from posterior nasopharynx	1.5–3.5 cm
Head diam	Diam of NP head allowing passage into posterior nasopharynx; must be sufficiently small for passage beyond inferior turbinate without catching on abnormal anatomy, such as septal spurs or a deviated nasal septum, but must otherwise maximize surface area for specimen collection	1–4 mm
Neck diam	A neck thinner than the head and shaft allows flexibility, easing manipulation of the swab in the posterior nasopharynx	1–2 mm
Neck length	Length of neck following the head tip prior to the shaft	3–3.5 cm
Break point location	A break point is a scoring or narrowing that allows the user to break the head off into the viral transport tube. This must be sufficiently easy that breaking can occur without need of, e.g., scissors and without excessive infection risk but not so easy as to risk breaking during insertion into the patient. Distance from head tip to break point must be less than the length of the tube (Fig. 1d, bottom left).	7–10 cm
Surface properties
Smoothness	Swabs should be sufficiently smooth to touch and minimally abrasive for patient comfort and safety. In particular, the tip should not be sharp, so as to prevent puncture injuries and minimize epistaxis risk.	Sufficient smoothness
Adhesiveness or residue	Swabs should not feel sticky or tacky or leave a residue behind with handling, as such residue could in principle have unwanted effects.	Not sticky
Odor	Swabs should not have an unusual chemical or metallic odor that could be an allergen or safety hazard to patients.	Must have a tolerable odor (e.g., no odor or very faint “plastic smell” is acceptable; strong, acrid, or glue smell is unacceptable)
Mechanical properties
Head and neck flexibility	Swabs must be flexible enough to be maneuvered into the posterior nasopharynx	Ability to bend head and, separately, neck at least 90 degrees without detachment. Ability of swab neck to revert to initial form following repetitive bending to 45° in both directions 45 times (Fig. 1d, top)
Durability/strength	Swabs must be durable enough to not break with reasonable manipulation	Ability to tolerate 20 rough repeated insertions into a 4 mm-inner-diam clear plastic tube curved with a radius of 3 cm (Fig. 1d, lower left)
Additional factors
Collection sufficiency	Swabs must be able to collect sufficient material for detection of viral nucleic acid. Collection sufficiency was approximated by Gram staining of an interior cheek swab compared to standard Copan swab (model 501CS01) as a control.	At least 10 clusters of bacteria/cells at ×40 magnification (Fig. 1c)
PCR compatibility	Swabs must not inhibit PCR	Swab material was incubated in standard viral transport medium overnight, spiked with 2× the limit of detection (200 copies/ml) of the SARS-CoV-2 amplicon target, and tested using the Abbott RealTime SARS-CoV-2 assay on the Abbott m2000 platform.