Specifications for swabs
There seem to be various groups testing various things on their swab prototypes. But:
What exactly should we test and how? What specifications do we actually require?
This is not only important for prototyping, but also for quality control (e.g. if mass production is outsourced).
Here is a probably incomplete list of things to think about:
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Collection: Of course, the swabs should collect material that most probably contain COVID19 viruses in infected patients. While viruses may be present in mucus, it seems like it is more reliable to actually pluck mucous cells. The target for a nasopharyngeal swab is the nasal concha. Once there, the swab must scrap the surface of the concha.
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Mechanical properties: The practitioner needs to insert and guide the swab all the way to the concha. Thus the swab should not be too rigid nor too soft (to be quantified).
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Head separation: Once out of the patient's body, the head must be detachable so it can be inserted in a test tube for the PCR. This is most easily achieved by having a weakness in the design so that the swab can be broken in two (very easy to do in PLA).
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Biocompatibility: The swabs should be made of a material that is not harmful for the patient (when used appropriately). Food-safe PLA should be ok. What about allergies?
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PCR compatibility: Once in the PCR, the swab itself should not interfere with the processes resulting in RNA multiplication.
As a warning, I want to stress that I am not a healthcare professional and all what's above is what I got from various discussions with ENT physicians and others. If I am writing something wrong, please correct me asap.
For each of the above points (and more to come I guess), one could come up with more precise requirement (volume of collected material? etc) and preferably easy-to-set-up testing protocols.