This important study from the WHO Infection Prevention and Control global unit was based on a multi-component intervention.[1] The intervention consisted of a number of specific measures, including not shaving the skin prior to surgery, antibiotic prophylaxis and proper skin preparation. It also included some generic cultural components, including the promotion of operating theatre discipline.
The incidence of post-operative infections of the surgical site was halved from 8% to about 4% following implementation of the intervention. No contemporaneous national initiative took place in any of the countries concerned, so I think that a general temporal effect, or rising tide,[2] is unlikely. Moreover, process measures improved in line with the clinical outcomes. A cause-effect explanation is thus plausible.
Yet, people will be properly sceptical of this result. Determining a surgical site infection (SSI) is subjective, as has been shown in many empirical studies.[3] Such measurements are likely to be reactive, meaning that there is an interaction between the intervention and the outcomes observed. The way to get around this is to objectify the observations in some way, such as by blinding the observers. Reactivity is a limitation on most studies of SSIs, whether randomised or observational. In my opinion, it is worth spending additional money to avoid this problem, which cannot simply be wished away. Possible methods to get around the problem include: use of observers who move from institution to institution and who do not know where or when interventions were implemented; or use of images scored blindly by independent observers. If this is too expensive, then independent sampling of wards taken at random by a truly blinded observer should be used. In the meantime, given the likely reactivity of the measurement, it is prudent to interpret RCTs of methods to reduce SSIs with caution.
— Richard Lilford, CLAHRC WM Director
- Allegranzi B, Aiken AM, Kubilay NZ, et al. A multimodal infection control and patient safety intervention to reduce surgical site infections in Africa: a multicentre, before-after, cohort study. Lancet Infect Dis. 2018; 18: 507-15.
- Chen YF, Hemming K, Stevens AJ, Lilford RJ. Secular trends and evaluation of complex interventions: the rising tide phenomenon. BMJ Qual Saf. 2016; 25: 303-10.
- Taylor JS, Marten CA, Potts KA, et al. What is the Real Rate of Surgical Site Infection? J Oncol Pract. 2016; 12(10): e878-83.