Why Are the LFT Swab Bristles Tube-like and Why Do They Stay in Your Body?

A few months ago, some people had a closer look at the swabs typically provided for carrying out lateral flow tests and wondered why the bristles broke away so easily and remained in your body. Here’s a good video demonstrating the issue.

One oddity was that the bristles appeared to be like tubes, and this raised the question of whether they were hollow, and what might be inside them.

Intrigued by the unusual composition of the swabs, Professor Anthony Brookes and Dr Kees Straatman from the University of Leicester put some material from one under a powerful laser microscope. The videos below show what they found. They explain:

To shed further light on the bristle structure of the swabs provided in LFD testing kits, we examined examples via confocal microscopy. The bristles were easy to separate from the swab itself, about 15 micrometres in diameter (the size of a large nucleus in a human cell), and clearly comprised an outer tube layer with an inner filling. The inner material does not seem to exude or flow or deviate from a cylindrical shape when the bristles are dissected, and so we would provisionally conclude this inner material is solid or semi-solid in nature.

It remains mysterious why the swabs would be manufactured in this strange way, and why they break away so easily when it should be straightforward to design a swab that remains intact and leaves no residue in the body. There is no evidence we are aware of that this swab design is harmful to health, but the design is still hard to understand and clarification from the manufacturer would be welcome.