Watch any news clip showcasing a laboratory working on COViD-19 Coronavirus and as the camera pans the lab you will spot laboratory technicians vortexing or sorting dozens of tubes with colored screw cap lids.
Those tubes are likely a 10mL transport tube which, at 80mm tall and 16mm wide, is the perfect size tube for storing the nasal swabs used to produce patient samples for COViD-19 testing.
Approved nasal swabs like the Puritan Purflock (SKU: 25-3320-H) come with a breakaway point at 80mm, and there are others with an even shorter break point, which fit easily into these transport tubes.
These 10mL transport tubes are then filled with a Viral Transport Media which protects and preserves the sample from the collection point until they can be tested at an approved COViD-19 testing center.
The problem is, there has been a mad rush on these and the USA supply has been depleted!
In the last few days we have been scrambling to identify a few suitable alternative transport tubes.
To be a candidate, the transport tube needs to meet the following qualifications.
1. RNase/DNase free - So there is no introduction of contaminants that would taint the sample
2. Sterile - For the same reason
3. For some customers, the tubes need to be of a specific height to accommodate robotic pipettors or other loading apparatus.
The most logical substitute would be the fairly common 15mL conical tube.
These are inexpensive, running about 14-15 cents a piece, are RNase/DNase free and sterile.
With a height of 118mm, it can be a hit or miss depending on the breakaway point of the nasal swab and the automated equipment.
For the most part we have found kit manufacturers avoiding 15mL conical tubes and only accepting them as a last resort.
Another alternative which has the right characteristics, but might not be compatible with automated loaders or robotic pipettors, are 4.5mL cryovials.
Cryovials are, by definition, RNase/DNase free and sterile.
With an overall height of about 89mm these come pretty close to being a good substitute, but the inner diameter runs between 9-11mm and some have raised the concern the fit is too tight for the nasal swab to fit properly.
With choices dwindling, the remaining option would be to search for a tube that might not be sterile, but could be sterilized through autoclaving; which means that both the tube and cap would have to be made from a sturdy plastic like polypropylene.
There are plenty of excellent non-sterile polypropylene 10mL tubes such as this one:
While these transport tubes are autoclavable, the caps are made from a softer and less durable polyethylene, which is not.
Which leads us to our final choice. Not ideal, but something worth considering:
A round bottom 5mL tube with screw-cap.
These transport tubes are 12 x 75mm which actually works quite well for nasal swabs, but they lack the ability to stand without the use of a tube rack or some other device.
However, as both the cap and the transport tube are autoclavable, a COVID-19 kit manufacturer could purchase these and autoclave them to bring them into compliance.
These last few days have been quite a journey and we've learned a lot about the different transport tube options.
Have questions? Give us a call 410-764-2225 and we'll share some additional information we've picked up.