PICO: the latest evidence to support best practice.

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In this podcast Chris Saunders discusses the findings of the latest meta- analysis  supporting the use of PICO for closed incisions in preventing surgical site complications.

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Welcome to Smith and Nephew's Closer to Zero podcast, a bimonthly podcast with leading experts in wound care hosted by Smith and Nephew, helping health care professionals in reducing the human and economic cost of wounds.

Hello, I'm Ruth Timmins from Smith and Nephew, and welcome to our podcast, which is looking at the latest evidence for PICO's single-use negative pressure wound therapy. We have Chris Saunders with us today, who recently published a meta-analysis on this. Chris graduated from the University of Edinburgh Medical School in 2012 and went on to do a PhD in infectious diseases at the University of York. He's always had an interest in clinical evidence and how it can be used to inform clinical decision-making and best practice. 

Since joining Smith and Nephew in 2016, Chris has spent his time identifying, critically analysing, and making sense of the evidence surrounding Smith and Nephew products. He now manages the evidence analysis team within the company and worked as part of the cross-functional team on the NICE guidance for PICO in 2019. So welcome, Chris, and thanks for joining us today.


Hi, Ruth, and thanks a lot for having me along.


So, you recently published this latest meta-analysis evidence, so perhaps you can give us an overview of the paper.


Yeah, I think that's a good place to start. So, this project really stemmed from a piece of work, which we've been working on with NICE to assess the evidence for PICO. So, NICE, for those that don't know, is a UK public body and NICE stands for the National Institute for Health and Care Excellence. So, their role is really to improve outcomes for people using the UK's National Health Service. So, they do this by producing evidence-based guidance and advice for practitioners, for commissioners, and managers, and to make their assessment, NICE is interested in both the clinical outcomes.


So, for example, how to get the best possible result for the patient, but also the economic arguments as well. So, we know it's clinically effective, but it also cost-effective, as an example. We set out with a question, what clinical benefits does PICO provide over the standard care when used for closed surgical incisions in patients at higher risk of complications? And keep in mind that surgical site complications still represent a significant burden to health care systems. So, this is really quite an important clinical question to ask. So as part of this, we needed to identify all the studies that were relevant to the topic. And we did this by performing what is called a systematic literature review. And we can go into the details about that a little bit later on.


Having identified the relevant evidence, we then pulled out information on clinical endpoints of interest. So, that's things like surgical site infections and other surgical site complications. We then performed what is called a meta-analysis to combine all of those different data points into an aggregated average. And this showed reductions in things like SSI, seroma, dehiscence, and necrosis for PICO when compared to the standard care. And it also led to reduction in the mean length of hospital stay for those patients as well.


OK, thank you. So, you mentioned that you performed a systematic literature review, and, you know, perhaps you could explain that a little bit and why it was performed here.


Yeah, certainly. So, a systematic literature review is a commonly used method to identify, select and critically analyse clinical evidence to answer a particular research question. So, in our case, that question was, what clinical benefits does PICO provide over the standard of care when used in closed surgical incisions in patients at higher risk of complications?


So our systematic literature review identified over 6,000 different studies which we needed to individually work our way through and work out whether they were relevant to this question or not. And that left us with 29 studies at the end of it. And the main benefits of performing a systematic literature review are, firstly, it's systematic, which means that we searched all of the main evidence databases for relevant clinical evidence. That includes PubMed, Embase, and the Cochrane Library. It's transparent, which means that we have clearly laid out keywords used for searches, the inclusion, exclusion criteria are available for everyone to see and the database is searched.


When we did the searches and things like that are all given so that we give enough detail so that anyone who is interested can replicate our searches and come up with that same list of 29 studies. And I think this is quite important because although this project was performed by Smith and Nephew employees, by performing a systematic literature review, what that means is that the results can be replicated by anyone using the same methodology that we've outlined in the manuscript.


Yeah. And so, if you are interested, our previous podcast went through about different levels of evidence, so that may be worth listening to, if you haven't heard that one. So, this systematic literature review, you said, identified 29 studies that were relevant. So, you went on to do a meta-analysis of the results. So, what is a meta-analysis, and why do it in this case?


So, a meta-analysis is a statistical technique that is commonly used in clinical research to combine the results of multiple different clinical studies into an aggregated figure. So that the studies you combine must be all looking at the same research question. It must be similar enough to be able to combine. So, they must have similar patient cohorts, similar research questions, similar outcomes that they're studying. And in the case of this manuscript, for example, we performed a meta-analysis of studies looking at surgical site infections. So, all of these studies were comparative in nature, they were all comparing PICO with the standard of care, and they all reporting on infection rates postoperatively.


So, if we look at each of those individual studies, for example, we know that in the Hyldig study there was a 52% reduction in the odds of a surgical site infection with PICO.(1) If we look at Karlakki, that was an 83% reduction(2), and Galiano, for example, there was a 34% reduction(3). And what a meta-analysis does is it allows you to make sense of all of those different numbers. So, we know that clinical studies always have variation or imprecision in the results they present. And that's natural because the human body is variable and not everyone responds exactly the same way to a treatment.


So, by combining all of the results from these individual studies, we first increase the confidence that we have in the ability of PICO to reduce SSIs and we can further get a more accurate percentage reduction associated with this. So, in this case, in this study, it was 63% reduction with PICO.(4)


OK, so what were the main findings, or the main results of the meta-analysis?


So, the main finding that we had was that 63% reduction in the odds of surgical site infections.(4) And this was statistically significant with a P value less than 0.001, which means we are very confident this is a real effect and not just a chance finding that we've come out of from this project. We also performed some sub-analysis, looking at individual surgical specialties. And this, again, showed a statistically significant difference in favour of PICO. And this was a case for orthopaedics, for obstetrics, for breast surgery and vascular surgery, which are their specialties which most of the evidence for PICO lies.


We also found a statistically significant reduction in the odds of dehiscence by 30%, seroma by 77%, and skin necrosis by 89%. And we did also look at other surgical site complications. (4)And I think for transparency, it's worth mentioning these as well. So, these are things like delays in healing, abnormal scarring, and a few other outcomes as well. And these perhaps showed a trend towards better results with PICO. But these results were not statistically significant, perhaps because of the smaller number of studies looking at these particular outcomes.


So, separately to these surgical site complications, but definitely related, we also found that there was a mean reduction in the length of hospital stay of 1.75 days for patients that had PICO compared to the standard of care. What this means is that patients with PICO were discharged home almost two days earlier than their counterparts that had standard dressings used instead.(4)


Some really interesting findings there and results. So, you know, what were the main strengths and perhaps potential weaknesses of the study, Chris?


Yes, a great question, Ruth, because I think it is important to note that every study, regardless of whether it's a level five study or level one study, every study has strengths and weaknesses. And I think it's important to take these into account when you're considering the merits and the ability of a study to be applied to your own patient population. So, if we start with some of the strengths of this study, I think probably the key strength is the depth and breadth of the evidence base for the use of PICO in closed surgical incision.


So, we had a good number of comparative studies in there. Many of these were those level one RCT, randomised controlled trials, which I think you talked about on the last podcast, and they all compared PICO with standard of care. So, we've got a good number of studies in there. And also the evidence base also includes several different surgical specialties. And the data comes from many different countries, making this more applicable and relevant to the general at-risk patient population. If we look at some of the weaknesses, and I would say that one weakness to highlight here is probably that we did include observational studies. So, we didn't just include those level one randomised control trials.


We also included lower levels of evidence as well. And these studies can be inherently subject to bias. But one thing to mention is that the observational nature of these studies can often provide high external validity. What this means is that the results of these studies are more easily applicable to the general patient population because a lot of these are in a less controlled clinical study. So some people would argue that the results are more applicable to the general patient population. So what this does is it gives a better idea of real-life results rather than relying solely on the results from those level one randomised control trials. One thing that gives us confidence, because I think there's different opinions about whether we should include observational studies, whether they should be excluded. One thing that gives us confidence that the inclusion of these studies didn't dominate the analysis was that the results of these studies were consistent with the results of the level one studies, which we included as well. We also performed what are called bias assessments for each of the studies included in the analysis, and this revealed relatively low bias for the observational studies included. So, overall, I think it is a potential weakness of the study, which we should certainly be aware of. But I think we've done everything we can to control that having a significant impact on the overall conclusions.


So, another thing to be aware of is that not every surgical specialty or patient group was included in this analysis. But again, the consistency and the results between different surgical specialties and patient groups gives us confidence that their effect in reducing surgical site complications is broadly applicable across the different groups. And one other thing just to mention on this is we were specifically looking at patients that were at higher risk of surgical site complications. And I think that's a good point to emphasise.


Hmm. Well, thanks for explaining that. So, do the results inform us which patients have the best results with PICO, Chris?


Yeah, so the majority of the patients in the studies included had risk factors that placed them at higher risk of surgical site complications. So, these are patient related factors like having a higher body mass index. There are patients who are perhaps smokers, those with underlying health conditions. And by that, we mean things like diabetes. And as well as patient-related factors, also procedural-related factors, so things such as prolonged duration of surgery, the use of implants, and complex surgery as well. So things like emergency surgery, for example, will always put a patient at higher risk of surgical site complications.


So, all of the studies and analysis included those patients that had either one or more risk factors that placed them at higher risk of surgical site complications. And this is really where PICO shines and is able to help those most vulnerable. In fact, some of the studies that we included in our meta-analysis, they had some sub-analysis within each of those individual studies where they've picked out those patients with the most risk factors for surgical site complications. And they've looked to see how PICO compared to standard care in those patients, what the results look like in those patients. And this is really where the biggest benefit of PICO can be seen.


So, what does this all mean? Well, PICO has the biggest benefit in those patients that are at higher risk of surgical site complications. So, really, patients should be risk assessed to identify those at highest risk of surgical site complications. And this should encapture both patient-related and procedure-related risk factors to get a full picture of that patient's individual risk profile. And finally, PICO should be used as part of a protocol to minimise those post-surgical risks.


So, you talked about the newly published manuscript, but how does this relate to the NICE guidance that was recently put out for PICO?


Yes, so this piece of work was part of the health technology assessment that we submitted to NICE. So, there was a package of clinical evidence, which is essentially the evidence which we present in this manuscript and what we've been talking about during this podcast. But in addition to this, NICE commissioned an independent working group to independently replicate and verify our findings.


So, this group came out with similar conclusions and the clinical outcomes to what we've discussed in this podcast. But as we mentioned at the start, NICE is interested in both the clinical outcomes and the economic outcomes. So NICE looked at economic modelling to determine whether the health economic argument for PICO stacked up. And this wasn't part of the clinical manuscript, which was recently published. But this economic analysis has recently been accepted for publication, so it will be available later on this year. And I wonder if this might be another piece of work, which some of your listeners might be interested in later on this year hearing about.


So, needless to say, PICO was shown to be both clinically and economically effective, resulting in NICE issuing guidance for PICO. And if we look at what NICE said in their guidance, they had three main recommendations. So, firstly, they state that the evidence supports the case for adopting PICO negative pressure wound dressings for close surgical incisions in the NHS. They're associated with fewer surgical site infections and seromas as compared with standard wound dressings. Secondly, they go on to say that PICO negative pressure wound dressings should be considered as an option for closed surgical incisions in patients who are at high risk of developing surgical site infections.(5)


And then finally they incorporate some of the health economic findings. And they say that cost modelling suggests that PICO negative pressure wound dressings provide extra clinical benefits at a similar overall cost compared with standard wound dressings. And this last point, in particular, I think is really important at a time when health care systems are stretched and they need to make best use of the resources that they have.


That's true, isn't it? And it's great to have such strong evidence to give the guidance of care. So, what would be the key take-home messages you'd like our listeners to go home with today?


So, I think there are a few key messages that I would like people to go away with. So, firstly, this is the strongest meta-analysis for PICO to date, and it includes evidence from 29 different comparative studies from a range of surgical specialties and geographical locations. So, we've got studies really represent a broad range of patients and regions of the world. The next thing is the main findings that we talked about.


So, some of those findings are that PICO, in comparison to standard wound dressings, reduces the odds of surgical site complications by an average of 63%. It reduces odds of dehiscence by 30%, seroma by 77%, and skin necrosis by 89%. (4) So, those findings were all found in patients with risk factors for surgical site complications, which we've also talked about. And this reduction in the surgical site complications helps to explain why we see that reduction in the mean length of hospital stay for patients as well. So, that was down by almost two days compared to those patients with standard dressings. Another important point, I think, is that PICO is still the only single-use negative pressure wound therapy device to get NICE guidance. And this is because of its strong clinical evidence base and good evidence to show that it's cost-effective.


And I think that if we take all of what we've discussed together and if you go through the manuscript, I think the results of this analysis really suggest that this technology warrants consideration by policymakers and health care professionals to really optimise those post-surgical wound treatment pathways to ensure that all patients, regardless of whether they have increased risk of surgical site complications, we need to make sure all patients have the best treatment, while making effective use of scarce health care resources.


So, thank you, Chris, for explaining that to us and giving us all that wonderful information. And don't forget to check out our online resources in the library attached to this podcast so you can have a look at those, and join us for our next podcast. Thanks for joining us. And thank you, Chris.


Thanks, Ruth.


Bye for now.


At Smith and Nephew, we are proud to help our customers get closer to zero surgical site complications and infection when it comes to treating high-risk closed incisions. Preventing and treating surgical site complications is vital to help reduce infection rates, prevent readmissions and improve patient outcomes. With our unique solution in PICO, this will promote faster healing and protect incisions against post-operative complications, with strong evidence across multiple specialties. The use of PICO has also shown a reduction in hospital length of stay and frequency of dressing changes, (4), helping our customers get closer to zero wasted health care resources. 


The information presented in this podcast is for educational purposes only. It is not intended to serve as medical advice. Products listed outline of care are examples only. Product selection and management should always be based on comprehensive clinical assessment, with detailed product information including indications for use, contraindications, precautions, and warnings. Please consult the product's applicable instructions for use prior to use.



1.Hyldig N, Vinter C, Kruse M, Mogensen O, Bille C, Sorensen JA et al. Prophylactic incisional negative pressure wound therapy reduces the risk of surgical site infection after caesarean section in obese women:a pragmatic randomised clinical trial. BJOG 2019;126:628–635

2.Karlakki SL, Hamad AK, Whittall C, Graham NM, Banerjee RD, Kuiper JH. Incisional negative pressure wound therapy dressings (iNPWTd) in routine primary hip and knee arthroplasties: a randomised controlled

trial. Bone Joint Res 2016;5:328–337

3.Galiano R, Hudson D, Shin J, van der Hulst R, Tanaydin V, Djohan R et al. Incisional negative pressure wound therapy for prevention of wound healing complications following reduction mammaplasty. Plast Reconstr Surg Glob Open 2018;6:e1560

4. Saunders C et al. Single-use negative-pressure wound therapy versus conventional dressings for closed surgical incisions: systematic literature review and meta-analysis BJS Open, 2021, 00, 1–8 DOI: 10.1093/bjsopen/zraa003

5.NICE PICO negative pressure wound dressings for closed surgical incisions Medical technologies guidance Published: 9 May 2019 www.nice.org.uk/guidance/mtg43

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Chris Saunders


Evidence Analysis Manager

Global Clinical Affairs, R&D

Smith + Nephew UK

Chris graduated from the University of Edinburgh medical school in 2012 and went on to do a PhD in infectious diseases at the University of York. He has always had an interest in clinical evidence and how it can be used to inform clinical decision making and best practice. Since joining Smith + Nephew in 2016, Chris has spent his time identifying, critically analysing and making sense of the evidence surrounding Smith + Nephew products. He now manages the Evidence Analysis team within the company and worked as part of a cross-functional team on the NICE guidance for PICO in 2019.

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