The Mölnlycke Health Care blog
Grading the evidence: Research questions and the mitigation of risk
In this final post in a series on evidence-based medicine, Hayley Hughes, a member of the clinical research team at Mölnlycke Health Care, will look at how posing a different research question may provide a more positive outcome for your intervention of choice.
Question: When is the outcome of a paper discussing your intervention not relevant to your needs?
Answer: When it is the wrong research question!
An inconclusive outcome for a particular healthcare intervention is still noteworthy when deciding on an intervention… but what if the article or systematic review that led to this conclusion was only looking at the proof of the virtually impossible?
During my MSc studies, researching the evidence used to make decisions on infection control practices, it was fairly evident that the most highly graded evidence was the Cochrane Review, a systematic review of randomized controlled trials (carried out independently by two individuals) and an intervention’s ability to reduce the incidence of surgical site infections (SSIs).
But because an SSI is caused by so many factors, the number of subjects needed to produce a significant result is a lot higher than looking at a reduction in bacterial load, for example. Therefore, more often than not, the outcome of each Cochrane Review was “an absence of evidence that the intervention prevents an SSI”. However, many of these interventions, e.g. surgical facemasks and surgical gowns, are included in the NHS Care Bundle for reducing SSIs1.
Obviously in the case of interventions, such as surgical face masks, it is fair to say that the NICE guidelines will not retract their recommendation because of the outcome from the review2, but in the case of interventions that are not currently advocated, e.g. washing with an antiseptic prior to surgery (an intervention that reduces the bacterial load on a patient prior to incision)3, an absence of evidence for reducing SSIs can often render the intervention not worth the expense to even consider advocating!
Reducing the risk
That said, the review on surgical face masks also concluded that they were shown to decrease contamination, even though this was not the primary research question.
With this in mind, why do we not choose practices based upon reducing the risk of getting an infection, rather than only relying on ultimate proof that these practices reduce infection rates? Too many times it seems like “reducing the risk” is perceived as just common sense and therefore just not good enough as evidence!
During my MSc this “common sense” answer was the outcome of many conversations with infection control nurses, especially in the case of washing with an antiseptic prior to surgery to reduce the risk of surgical site infection, but it was the initial blanket expense of such an intervention that prevented it being brought into local practice, even though the cost of treating one patient with an SSI was much higher.
In 2012, Judith Tanner and colleagues published an RCT on antiseptic whole-body washing comparing chlorhexidine with a similar antiseptic in addition to soap and water4. However, like the methodology in earlier Swedish studies5,6, this team did not check the overall bacterial load on the skin, but provided evidence to support the efficacy of the procedure in decreasing the bacterial count at high sources of residential bacteria, e.g. the groin or armpits, therefore reducing the risk that the bacteria can migrate from these areas to the site of surgical incision and potentially cause an SSI.
All the care bundle measures in hospitals are carried out to prevent the risk of infection, so why not advocate a practice that reduces the risk, of which there is ample evidence, rather than solve the multifactorial problem of SSIs outright by itself? Common sense in this instance seems justified, doesn’t it?
When you next dismiss a study for its absence of evidence for your intervention, critically analyse it to see if it actually provides evidence for a reduction in risk… because a different research question may help focus us all on the newly christened, but long-held belief amongst healthcare workers of “patient-centred care”.
Other articles in the same series:
- National Institute for Health and Clinical Excellence (NICE) (Oct 2008) Prevention and Treatment of Surgical Site Infection, 'Clinical Guideline 74', http://www.nice.org.uk/nicemedia/pdf/CG74NICEGuideline.pdf.
- Lipp, A. and Edwards, P. (2012) Disposable surgical face masks for preventing surgical wound infection in clean surgery, 'Cochrane Database of Systematic Reviews', John Wiley & Sons, Ltd.
- Webster, J. and Osborne, S. (2011) 'Preoperative bathing or showering with skin antiseptics to prevent surgical site infection', Cochrane Database of Systematic Reviews, no. 3.
- Tanner, J., Gould, D., Jenkins, P., Hilliam, R., Mistry, N. and Walsh, S. (2012) 'A fresh look at preoperative body washing', Journal of Infection Prevention, vol. 13, no. 1, pp. 11-15.
- Brandberg, A. and Anderssson, I. (1979) 'Whole Body Disinfection by Shower-Bath with Chlorhexidine Soap', Control of Hospital Infection: Royal Society of Medicine Internation Congress and Symposium Series No.23, London, London, Acaedimc Press inc and Royal Society of Medicine, pp. 65-70.
- Byrne, D.J., Napier, A., Phillips, G. and Cuschieri, A. (1991) 'Effects of whole body disinfection on skin flora in patients undergoing elective surgery', Journal of Hospital Infection, vol. 17, no. 3, pp. 217-222.