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Tackling the diagnostic testing sustainability problem

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A leading researcher has called on the World Health Organization to set limits on the amount of waste generated by disposable diagnostics.

Maïwenn Kersaudy-Kerhoas is a professor of microfluidic engineering and leads the Global Research Institute in Health and Care Technologies at Heriot-Watt University.

She said: “The urgency of the pandemic led us to lose focus on environmental sustainability in the area of medical diagnostics and it is time to redress the balance between medical need and sustainability.”

Health Tech World called up Prof. Kersaudy-Kerhoas to find out more.

HTW: Hi Professor Kersaudy-Kerhoas. How big a problem is sustainability in diagnostic testing?

In my practice, I develop a lot of single-use, plastic, disposable devices. And I’m not the only one.

The field of point-of-care (PoC) testing is full of these single-use disposable cartridges. 

They are they are extremely useful because they enable broader access to diagnostics than has been the case in the past. 

But nobody has looked at what we do after we use them. We throw them away and bury or incinerate them.

The Cepheid GeneXpert cartridge is a prime example of PoC tests, especially in low and middle income countries (LMICs.) 

There were 24 million produced in 2020. But that’s just one type of cartridge for COVID tests. 

They have about 24 different types of cartridge for each disease, equating to more than 1,680 tonnes of plastic per year. 

And at the opposite end of the spectrum, we have lateral flow assays. 

A conservative estimate is that we produce two billion lateral flow assays [per year]. 

I got this figure from a 2018 paper, so before the pandemic. That’s 40,000 tonnes of plastic per year. 

We were totally ignoring this. 

But what the pandemic did was bring the issue of medical waste into focus in the media and among the broader public, when we saw these big bags of PPE, and so on.

Now, PoC tests are only a fraction of this, but it’s still important that we consider our footprint at the design stage, so we make the right choices in terms of material, design, where it’s manufactured and where it’s going.

What about other kinds of waste?

We’ve seen shocking examples of electrical waste, even in lateral flow assays. 

For example, there’s a product which is sold in Australia and in the US, which is called the Ellume test. 

These tests have a single use PCB and a battery button for a single use test. 

Prof. Maïwenn Kersaudy-Kerhoas

We’ve collaborated with Alice Street at the University of Edinburgh to dismantle 20 different tests.

And this particular test was the hardest to take apart. 

The battery button was the hardest thing to dismantle, so who’s going to do that? The batteries will just end up in landfill.

It’s the same with Covid tests and also things like pregnancy tests, where we went from simple, paper devices to plastic devices with battery components. 

On top of that, there’s also chemical waste associated with PoC devices, such as a chemical called guanidine thiocyanate, which is present in a lot of molecular base tests for HIV, TB and so on.

The presence of these chemicals means that these cartridges need to be incinerated at over 850 degrees. 

The problem is that these cartridges test for diseases that are highly prevalent in LMICs. 

The cartridges themselves have been developed with this market in mind, but nobody has thought about what people will do after the test is used. 

How are you working towards finding alternatives to this?

As an engineer, I’m thinking about the design of these devices, and also the material that we use for them. 

There’s been a lot of progress in paper microfluidics, where, instead of using plastic substrate, we use paper substrates. 

When it was first introduced by George Whitesides back in 2010, it was touted as a more environmentally friendly solution. 

But, again, people have forgotten about the sustainability side of the solution and have started adding more and more plastic to their paper device. 

There’s some really good devices demonstrated in the literature. Now, what we have to do is show that we can mass manufacture them. We’re not there yet.

When I talk to lateral flow assay manufacturers, it’s not a black and white picture.

They know they have sustainability issues, but they don’t have the resources to address these. That’s why academia is there, to bridge the gap and do the research. 

But at some point, it will also need investment from government and funders to develop these high volume manufacturing lines for more sustainable products.

I guess with every solution, there’s so many variables. How is this going to endure? How will you transport it? How can you be consistent with the manufacturing? Lots of considerations to juggle… 

Yeah, absolutely. We have to make our assays robust enough that they can work on different substrates. 

Ideally, you might want to do wood in a certain country that has a lot of these resources where you don’t need to transport material from halfway around the planet.  

And in some other countries, you will have more natural plastic derivatives. 

We have to adapt to the natural resources that are around us. It does create challenges but it’s really interesting research as well. 

You’ve called on the World Health Organization to set limits on the amount of waste from disposable diagnostics.

Could you expand on that? And what else can be done at a local, national or international level to address this issue?

The target product profile, or TPP lists a set of requirements that have to be met by the product. For example, they set sensitivity and specificity limits.. 

These TPPs are hugely influential on the manufacturers and on the products that end up with on the market. 

My colleague, Alice Street, did a survey of these TPPs, and found that less than 25 per cent have any sort of information on the environmental sustainability of the device. 

When we did the survey on the lateral flow assay cartridge, we found that the average is about 3.5 grammes per cartridge, but there can be a huge variation.

We could use this average as a quantitative limit in the TPP.

First of all, it would give the industry a guideline and then it can force the direction of travel so that people have to use less than the average that we’re using at the moment. 

That’s work that we want to pursue and we’re engaged with a number of manufacturers and organisations that are really behind these things.

So presumably, you’ve got partnerships with developers of these technologies? 

Yes. In fact, I was talking this morning with a Dutch startup that has developed this cartridge [made of] a bio-derived plastic.

There’s a lot of work to be done to prove to manufacturers that this can work. 

We know that a lot of these can be moulded.  It’s about demonstrating that the test is as effective as the virgin plastics that are used at the moment. 

And then there’s also an economic element, a regulatory element and  the human behaviour element.

At the moment, these plastic alternatives are more expensive. So if that’s the case, can we convince the NHS that this added cost is actually going to be beneficial along the line because the carbon footprint will be less?

Then there’s the regulatory element. 

Now, there’s no reason why we couldn’t use recycled plastics to make these lateral flow assay cassettes.

But when you tell that to manufacturers, they’re like, ‘oh, no, no, we have to use virgin plastic.’

But I haven’t been able to pinpoint exactly where it is written that we have to do this. 

I think there’s an element of research around the regulation, and possibly then influencing a change in the regulation to allow these recycled plastics to be used. 

And finally, there’s a human behaviour element.

If you had the choice between two devices, which would you use?

You might see the brownish [naturally-derived or recycled] one as dirty, for example. 

So it’s not just the technical work. There is also social science work to bringing in more sustainable alternatives. 

So, where are you taking your research next into 2024?

We’re really excited to partner with an English moulder, Great Central Plastics in Manchester. 

We’re producing LFA cartridges in five different bio plastics, including GUM-TEC, which is plastic made out of chewing gum collected from the streets of England.

We’re not suggesting that these lateral flow assays have to be made in these sorts of plastics, but we want to use these as demonstrators of the things that can be done.

Is there enough of this type of plastic to make 2 billion cartridges a year? Surely not.

But can this still be an economical solution in a certain part of the world? 

The research is about creating this demonstrator and sparking the debate around the sort of material we use in these sorts of devices. 

Anyone interested in collaborating with the new Health and Care Technologies global research institute at Heriot-Watt University can contact [email protected]

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