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Wound-edge protection devices for preventing surgical site infection in abdominal surgery

  1. Thomas D Pinkney1,*,
  2. John McCall2,
  3. Jo C Dumville3,
  4. Francesca J Edwards2,
  5. Adrian Gheorghe4,
  6. David C Bartlett5,
  7. Benjamin R Fletcher4,
  8. Melanie J Calvert6

Editorial Group: Cochrane Wounds Group

Published Online: 24 JUN 2013

DOI: 10.1002/14651858.CD010614


How to Cite

Pinkney TD, McCall J, Dumville JC, Edwards FJ, Gheorghe A, Bartlett DC, Fletcher BR, Calvert MJ. Wound-edge protection devices for preventing surgical site infection in abdominal surgery (Protocol). Cochrane Database of Systematic Reviews 2013, Issue 6. Art. No.: CD010614. DOI: 10.1002/14651858.CD010614.

Author Information

  1. 1

    University Hospitals Birmingham, Academic Department of Surgery, Birmingham, UK

  2. 2

    Dunedin School of Medicine, University of Otago, Department of Surgical Sciences, Dunedin, New Zealand

  3. 3

    University of Manchester, Department of Nursing, Midwifery and Social Work, Manchester, UK

  4. 4

    University of Birmingham, Primary Care Clinical Sciences, Birmingham, West Midlands, UK

  5. 5

    University of Birmingham, NIHR Biomedical Unit and Centre for Liver Research, Birmingham, West Midlands, UK

  6. 6

    University of Birmingham, School of Health and Population Science, Birmingham, UK

*Thomas D Pinkney, Academic Department of Surgery, University Hospitals Birmingham, Queen Elizabeth Hospital, Mindelsohn Drive, Edgbaston, Birmingham, NG7 2UH, UK. thomas.pinkney@tiscali.co.uk.

Publication History

  1. Publication Status: New
  2. Published Online: 24 JUN 2013

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This is not the most recent version of the article. View current version (09 JUN 2015)

 

Background

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support

Surgical site infection (SSI) is an infection of the wound following a surgical procedure. These infections can be categorised into superficial (skin and subcutaneous tissue), deep incisional (fascia and muscle) and organ space infection (involving manipulated internal parts) (Mangram 1999). SSI is the most frequent cause of nosocomial infection in surgical patients, accounting for 38% of all infections (Mangram 1999) and its occurrence confers a significant impact on patient mortality and morbidity rates as well as healthcare costs. A US study found that in over 750,000 episodes of surgical hospitalisation, 1% resulted in a SSI (de Lissovoy 2009), and similar estimates have been found in France (Astagneau 2009). A UK-wide prevalence survey of over 75,000 patients showed that 3.7% to 5.4% of patients undergoing a surgical procedure developed a SSI (Smyth 2008). It should be noted that all these figures are based on passive and retrospective surveillance and are reliant on the accurate coding or recording of SSI signs and symptoms. As such they are likely to significantly under-represent the true incidence of this complication.

The risk of developing SSI has been shown to be multifactorial. Surgical wound type is one such factor first categorised by the National Research Council in 1964 (NRC 1964). Under this system wounds may be classified as 'clean', 'clean-contaminated', 'contaminated' and 'dirty'.

  • Clean wounds are defined surgical wounds in which the bronchi, gastrointestinal tract or genitourinary tract was not entered. The incidence of SSI in clean wounds is less than 2% and is most commonly due endogenous Staphylococcus aureus present on the skin.
  • Clean-contaminated wounds are defined as surgical wounds in which the bronchi, gastrointestinal tract or genitourinary tract was breached, but without unusual contamination. Elective intestinal resection, pulmonary resection, gynaecologic procedures and head-neck cancer operations that involve the oropharynx are examples of clean-contaminated procedures. SSI incidence for these procedures is in the range of 4% to 10%.
  • Contaminated wounds are defined as fresh traumatic wounds or surgical wounds where there has been a breach in sterile technique or acute, gross spillage from gastrointestinal tract or nonpurulent inflammation is encountered. Infection rates in contaminated wounds exceed 10% even with antibiotic prophylaxis.
  • Finally dirty wounds are old traumatic wounds involving abscesses or perforated viscera. Abdominal exploration for acute bacterial peritonitis and intra-abdominal abscess are examples of this class of surgical site infection (NNIS 2004; NRC 1964).

In addition to this stratification by contamination level, the site of surgery and structures operated upon also play an important role in the likelihood of developing a SSI. Abdominal surgery carries one of the highest rates of SSI, particularly if the operation involves the colon or rectum (Blumetti 2007; Smyth 2008). Recent studies exploring the rate of SSI after open colorectal surgery have found a very similar incidence of 25% (Blumetti 2007), 25.3% (Howard 2010) and 24.9% (Serra-Aracil 2011).

Other co-factors associated with an increased risk of SSI include a compromised immune system (including diabetes, malnutrition, immunosuppressive therapy or HIV), increased risk of endogenous contamination (positively correlated to the duration of the operative procedure) and type of operation (procedures involving tissue with high concentrations of bacterial flora such as the bowel) (NICE 2008).

SSI is associated with considerable morbidity, a reduction in quality of life and increased healthcare costs, placing a significant burden on healthcare systems and individuals. In a study of 38,973 patients in Northern France over a three-year period, SSI was found to be an independent predictor of mortality, with mortality due to SSI reported in 78 patients (0.2%) (Astagneau 2001). In 2002 there were 8205 deaths in the US due to SSI, accounting for 8% of all deaths caused by a nosocomial infection, with SSI listed as one of the most common causes of multiple system organ failure (Klevens 2007; Mangram 1999).

SSI has also been shown to significantly increase the duration and cost of patient hospitalisation, predominantly due to re-operation, additional nursing care and drug treatment costs (Mangram 1999; Wilson 2004). In a case-controlled US study of 255 patient pairs, it was found that in those patients with SSI, hospital discharge was delayed by an average of 6.5 days (95% confidence interval (CI) 5 to 8 days) with an additional direct cost of USD 3089 per patient (Kirkland 1999). In a further Swiss study of 6283 surgical procedures, 187 SSIs were reported, of which 168 were successfully matched with a control patient. In patients with SSI, the mean additional hospital cost was CHF 19,638 (95% CI CHF 8492 to CHF 30784) and the mean additional length of hospitalisation was 16.8 days (95% CI 13 to 20.6 days) (Weber 2008). In the UK, length of stay is typically doubled and additional costs of GBP 814 to GBP 10,523 are incurred in patients with a SSI (Coello 2005; NICE 2008; Plowman 2001; Tanner 2009). The indirect costs of SSI, due to loss of productivity, patient dissatisfaction and litigation, and reduced quality of life, have been studied less extensively.

As the majority of SSIs are the result of bacterial contamination of a wound stemming from endogenous flora from the patients skin, mucous membranes or hollow viscera, the idea of using a physical barrier to cover the cut edges of the surgical wound has been revisited several times over the last 40 to 50 years. This protection can take the form of a wound-edge protection device (WEPD) or 'wound-guard' which is inserted into the wound for the duration of the operation.

This review aims to assess the clinical effectiveness of wound-edge protection devices (WEPDs) in reducing the SSI rate in patients undergoing open abdominal surgery.

 

Description of the condition

Whilst SSIs can be difficult to define - one review identified 41 different definitions and 13 SSI grading scales (Bruce 2001) - the Centers for Disease Control and Prevention (CDC) have published the following guidelines defining superficial and deep incisional SSIs (Horan 2008).

A superficial SSI is defined as: an infection occurring within 30 days after the operation and only involving the skin and subcutaneous tissue of the incision that is associated with at least one of the following.

  • Purulent drainage, with or without laboratory confirmation, from the surgical site.
  • Organisms isolated from an aseptically obtained culture of fluid or tissue from the surgical site.
  • At least one of the following signs or symptoms of infection: pain or tenderness, localised swelling, redness or heat, and superficial incision is deliberately opened by the surgeon and is culture-positive or not cultured. A culture-negative finding does not meet this criterion.
  • Diagnosis of SSI by the surgeon or attending physician.

A deep incisional SSI is defined as: infection that occurs within 30 days after the operative procedure if no implant is left in place, or within one year if an implant is left in place, and the infection appears to be related to the operative procedure and involves deep soft tissues (e.g. fascial and muscle layers) of the incision associated with one of the following.

  • Purulent drainage from the deep incision, but not from the organ/space component of the surgical site.
  • A deep incision spontaneously dehisces (opens up) or is deliberately opened by the surgeon and is culture-positive or not cultured when the patient has at least one of the following symptoms: fever or localised pain or tenderness.
  • An abscess, or other evidence of infection involving the deep incision is found on direct examination, during re-operation, or by histopathologic or radiologic examination.
  • Diagnosis of a deep incisional SSI by a surgeon or attending physician.

Other systems have been used to diagnose or classify SSI including the ASEPSIS system and providing these are validated and predominantly based upon a clinical diagnosis of SSI they will be included in this review. We will exclude purely bacteriological definitions of SSI because the current clinical guidelines (CDC 1999; NICE 2008) specify definitions of SSI based predominantly on clinical signs and because it is difficult to differentiate infection from contamination when interpreting the positive results of swab cultures (Gurevich 1995; Peel 1991).

 

Description of the intervention

Wound-edge protection devices (WEPDs), also known as 'wound guards', have been used in abdominal surgery for more than 40 years (Maxwell 1969). There are several different devices on the market but they have the same basic design - a semi-rigid plastic ring placed into the abdomen via the laparotomy wound to which an impervious drape is circumferentially attached. This plastic drape comes up and out of the wound onto the skin surface, thus protecting the cut wound edges. WEPDs create a physical barrier between the abdominal wound edges and viscera, visceral contents, contaminated instruments and gloves, thereby preventing wound contamination. A wound protector may also provide a degree of mechanical retraction of the incisional edges.

Despite their potential for reducing SSIs when used intra-operatively, by protecting the wound margins from contact with any contaminated materials, they have never become common practice and they are not mentioned in the current UK clinical guidelines. It should be noted that WEPDs are distinct from 'adhesive drapes': the latter are plastic drapes adherent to the superficial surface of the skin and they do not come into direct contact with the internal wound margins, i.e. the cut edge of skin, fat and fascia/muscle.

 

How the intervention might work

The proposed mechanism of action of a WEPD is two-fold. Firstly, they create a physical barrier between the abdominal wound edges and viscera, visceral contents, contaminated instruments and gloves, thus reducing accumulation of endogenous and exogenous bacteria on the wound edges. They also potentially reduce tissue necrosis from long procedure exposure as well as performing a degree of mechanical retraction which in turn may reduce the need for handheld mechanical retraction and the tissue damage associated therein. Smaller versions of wound-edge protection devices are also currently often used in laparoscopic-assisted resections of colorectal malignancies to prevent seeding of tumour cells into wound edges - this potential role is not relevant to this review.

It can be hypothesised that WEPDs may be particularly beneficial in procedures with an increased risk of endogenous contamination such as clean-contaminated, contaminated or dirty procedures where, by definition, there will be greater bacteriological concentrations contained within the operative field.

The effectiveness of the physical barrier WEPDs provide over the wound edges in reducing numbers of bacterial pathogens present was first reported more than 40 years ago (Harrower 1968) and corroborated more recently by Horiuchi 2010 who found that all incision margin cultures from patients where a WEPD had been used yielded no growth of organisms.

 

Why it is important to do this review

SSI places a significant burden on healthcare systems globally due to increased hospitalisation, additional operative and nursing costs and drug treatment requirements. SSI is associated with significant morbidity and mortality and can have a significant impact on individuals' well being, causing persistent pain, cosmetically unacceptable scars and restriction of movement (NICE 2008).

Guidelines concerning the prevention of SSI have been issued in the UK by the National Institute for Health and Clinical Excellence (NICE 2008) and in the USA by the Centers for Disease Control and Prevention (CDC 1999). These recommendations are based on systematic reviews of best available evidence, or when minimal evidence is available the guideline development group’s opinion of what constitutes good practice. Intra-operative guidance includes the role of hand decontamination, sterile gowns and drapes, and antiseptic skin preparation. The concept of a WEPD is not discussed in these guidelines.

 

Objectives

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support

To compare the effects of WEPDs in the prevention of SSI in patients undergoing abdominal surgery.

 

Methods

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support
 

Criteria for considering studies for this review

 

Types of studies

Published or unpublished randomised controlled trials (RCTs) that compare the use of an intra-operative WEPD with standard care or comparing alternate types of WEPD in patients undergoing abdominal surgery. We will include any RCT where the use of a WEPD is the only systematic difference between trial arms.

 

Types of participants

Studies involving patients of any age undergoing abdominal surgery.

 

Types of interventions

The primary intervention is the use of a WEPD. For the purpose of this review, a WEPD is considered eligible if it covered the wound's cut edges with an impervious plastic sheet. We will exclude studies evaluating adhesive drapes which, unlike WEPDs, adhere to the superficial surface of the skin and do not come into direct contact with the internal wound margins, i.e. the cut edge of skin, fat and fascia/muscle.

 

Types of outcome measures

 

Primary outcomes

  • Postoperative SSI: any standard definition of postoperative SSI based on clinical findings (e.g. CDC criteria) diagnosed within 30 days of operation. We will exclude purely bacteriological definitions of SSI. We will not differentiate between superficial, deep incisional and organ space infection.
  • Adverse events relating to use of the WEPD, as defined and categorised in individual studies.

 

Secondary outcomes

  • Cost-effectiveness: including measures of resource use such as duration of hospital stay, operation duration, use of antibiotic or analgesic drugs, dressing costs and nursing time, all in relation to the index admission for the operation during which the intervention (WEPD/control) was used.
  • Pain within 30 days of operation, measured using survey/questionnaire/data capture process or visual analogue scale in individual studies.
  • Health-related quality of life (measured using a standardised generic questionnaire such as EQ-5D, SF-36, SF-12 or SF-6 or disease-specific questionnaire). We will not include ad hoc measures of quality of life which are likely not to be validated and will not be common to multiple trials. Measured any time from the operation up to one year.
  • Other wound complications such as wound dehiscence and incisional hernia - measured within one year of operation.
  • Mortality.

 

Search methods for identification of studies

 

Electronic searches

We will search the following electronic databases:

  • the Cochrane Wounds Group Specialised Register (latest issue);
  • the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, latest issue);
  • Ovid MEDLINE (1948 to latest issue);
  • Ovid MEDLINE (In-Process & Other Non-Indexed Citations, latest issue);
  • Ovid EMBASE (1974 to latest issue);
  • EBSCO CINAHL (1982 to latest issue).

We will combine the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity- and precision-maximising version (2008 revision); Ovid format (Lefebvre 2011). We will use the Ovid EMBASE filter developed by the UK Cochrane Centre (Lefebvre 2011) and combine the CINAHL search with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN) (SIGN 2011). There will be no restrictions on the basis of date or language of publication.

We will use the following search strategy to search CENTRAL:

1 (wound* adj protect*).tw.
2 wound edge protect*.tw.
3 (wound* adj guard*).tw.
4 wound drape*.tw.
5 ring drape*.tw.
6 ((drape or barrier) adj protect*).tw.
7 (ViDrape or Vi Drape or Steri Drape or SteriDrape or Alexis).tw.
8 or/1-7
9 exp Surgical Wound Infection/
10 exp Surgical Wound Dehiscence/
11 (surg* adj5 infect*).tw.
12 (surg* adj5 wound*).tw.
13 (surg* adj5 site*).tw.
14 (surg* adj5 incision*).tw.
15 (surg* adj5 dehisc*).tw.
16 (wound* adj5 dehisc*).tw.
17 wound complication*.tw.
18 exp Bacterial Infections/
19 exp Postoperative Complications/
20 or/9-19
21 8 and 20

We will search the following ongoing trials databases:

 

Searching other resources

We will search the bibliographies of all retrieved and relevant publications identified by these strategies for further studies. We will not perform handsearches for this review since they are conducted by the Cochrane Wounds Group in order to populate the Cochrane Central Register of Controlled Trials (CENTRAL), which will be searched. We will also contact manufacturers regarding studies for inclusion including: 3M ('Steri-drape' wound edge protection drape), Applied Medical ('Alexis' device) and Medical Concepts Development (MCD) ('Vi-Drape' device).

 

Data collection and analysis

 

Selection of studies

Two review authors will independently assess the study titles and abstracts against the review inclusion criteria. After this initial assessment, we will obtain all studies that might potentially meet these criteria in full. Two review authors will check the full papers for eligibility, with disagreements being resolved by discussion and, where required, the input of a third review author. We will extract details of the eligible studies and summarise them on a data extraction sheet. Two review authors will extract data independently. If data are missing from reports, we will make attempts to contact the study authors to obtain the missing information. Studies published in duplicate will be included once, but we will extract the maximum amount of data from the papers. This process will be followed by all review authors, with at least two review authors working independently. We plan to include a study flow diagram as recommended by the PRISMA statement (Liberati 2009) to illustrate the results of all searching activity and the process of screening and selecting studies for inclusion in the review.

 

Data extraction and management

Two review authors will extract all data independently. We will extract the following data.

  • Country of origin of trial.
  • Type of surgery.
  • Classification of surgical contamination.
  • Eligibility criteria and baseline participant data.
  • Details of the protector/treatment regimen received by each group and any co-interventions.
  • Primary and secondary outcome(s) (with definitions).
  • Outcome data for primary and secondary outcomes (by group).
  • Duration of follow-up.
  • Number of withdrawals (by group).
  • Source of funding for trial.

 

Assessment of risk of bias in included studies

Two review authors will independently assess each included study. We will undertake assessment using the Cochrane Collaboration tool for assessing risk of bias (Higgins 2011). The 'Risk of bias' tool considers six domains: sequence generation, allocation concealment, blinding, incomplete outcome data, freedom from selective reporting and other issues (e.g. fraud). Please see Appendix 1 for details of the criteria on which the judgement will be based. We will complete a 'Risk of bias' table for each eligible study; we will combine these data into a 'Risk of bias' summary figure where judgements for each domain are tabulated by study. We will consider all risk of bias domains equally, but for the purpose of the proposed sensitivity analysis we will classify trials as being at overall high risk of bias if they are rated 'high' for any one of three key criteria, i.e. randomisation sequence, allocation concealment and blinded outcome assessment.

 

Measures of treatment effect

We will present results with 95% confidence intervals (CI). We will report estimates for dichotomous outcomes (e.g. infected: yes/no) as risk ratios (RR) (Deeks 2002). We will report continuous data (e.g. pain) as mean differences (MD) and we will calculate overall effect sizes (with 95% CI). We will record the adverse events reported and present this information narratively, we will report the data as count data if available. 

 

Dealing with missing data

The problem of missing data is common in trials, especially those of poor quality. Excluding participants from the analysis after randomisation, or ignoring participants lost to follow-up can, in effect, undo the process of randomisation and thus, potentially, introduce bias into the trial. For our primary outcomes, SSI and adverse events, we will assume that where randomised participants are not included in an analysis, they did not have a SSI or other adverse event(s)(that is they were considered in the denominator but not the numerator). Given the relatively small number of SSI or adverse events anticipated, this seems the most appropriate assumption. However, we will test this assumption in a sensitivity analysis where we will assume participants excluded post-randomisation to have developed the outcome (i.e. included in both the numerator and the denominator). Where a trial does not specify participant group numbers prior to dropout, we will only present complete case data. We will present data for all secondary outcomes as complete case analysis.

 

Data synthesis

We will explore both clinical and statistical heterogeneity and the decision to include studies in a meta-analysis will depend on the availability of treatment effect data and assessment of heterogeneity.

We will also summarise data for each comparison by compiling 'Summary of findings' tables in GRADEprofiler: all outcomes will be included. We will estimate control group event rates for patients at medium risk of SSI using the average risk of SSI in the included studies; we will investigate the potential of estimating control group event rates for patients at high risk of SSI using data from studies with populations at particularly high risk, e.g. based on surgery type.

 

Subgroup analysis and investigation of heterogeneity

We will assess statistical heterogeneity using the Chi² test (we will consider a P value significance level of less than 0.1 to indicate heterogeneity). We will consider the I² statistic which examines the percentage of total variation across studies due to heterogeneity rather than to chance. Values of I² over 50% may represent substantial heterogeneity (Higgins 2003). In the absence of clinical heterogeneity, we will perform a meta-analysis using a fixed-effects model. Where there is likely clinical heterogeneity, we will apply a random-effects model. Where possible we will assess the influence of the degree of contamination (clean/clean-contaminated/contaminated/dirty) on the impact of wound protectors on SSI rate.

Should data be available we will undertake subgroup analyses comparing open and laparoscopic surgery.

 

Sensitivity analysis

We will undertake a sensitivity analysis to investigate the effects of removing studies at high risk of bias from the analysis, studies at high risk of bias being those which do not adequately define random sequence generation, allocation concealment methods and blinding of outcome assessor. We will undertake a sensitivity analysis to investigate the way that missing data was dealt with as detailed in the Dealing with missing data section.

 

'Summary of findings' table

We will present the main results of the review in summary of findings tables, which provide key information concerning the quality of evidence, the magnitude of effect of the interventions examined, and the sum of available data on the main outcomes, as recommended by the Cochrane Collaboration (Schunemann 2011a). We plan to include the following main outcomes in the summary of findings tables:

  1. surgical site infection;
  2. health-related QOL and cost-effectiveness
  3. wound complications, adverse events.

The summary of findings table includes an overall grading of the evidence related to each of the main outcomes, using the GRADE approach (Schunemann 2011b).

 

Acknowledgements

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support

We would like to acknowledge Jenny Bellorini, the copy editor of this protocol, the external peer referees (Anne-Marie Bagnall, Malcolm Brewster, Beryl de Souza and Elmer Villanueuva) and the Wounds Group Editors (Kurinchi Gurusamy and Dirk Ubbink).

 

Appendices

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support
 

Appendix 1. Appendix 1 - Assessment of risk of bias in included studies

 

1. Was the allocation sequence randomly generated?

 
Low risk of bias

The investigators describe a random component in the sequence generation process such as: referring to a random number table; using a computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots.

 
High risk of bias

The investigators describe a non-random component in the sequence generation process. Usually, the description would involve some systematic, non-random approach, for example: sequence generated by odd or even date of birth; sequence generated by some rule based on date (or day) of admission; sequence generated by some rule based on hospital or clinic record number.

 
Unclear

Insufficient information about the sequence generation process to permit judgement of low or high risk of bias.

 

2. Was the treatment allocation adequately concealed?

 
Low risk of bias

Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent method, was used to conceal allocation: central allocation (including telephone, web-based and pharmacy-controlled randomisation); sequentially numbered drug containers of identical appearance; sequentially numbered, opaque, sealed envelopes.

 
High risk of bias

Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation based on: using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate safeguards (e.g. if envelopes were unsealed or non opaque or not sequentially numbered); alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure.

 
Unclear

Insufficient information to permit judgement of low or high risk of bias. This is usually the case if the method of concealment is not described or not described in sufficient detail to allow a definite judgement, for example if the use of assignment envelopes is described, but it remains unclear whether envelopes were sequentially numbered, opaque and sealed.

 

3. Blinding - was knowledge of the allocated interventions adequately prevented during the study?

 
Low risk of bias

Any one of the following.

  • No blinding, but the review authors judge that the outcome and the outcome measurement are not likely to be influenced by lack of blinding.
  • Blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
  • Either participants or some key study personnel were not blinded, but outcome assessment was blinded and the non-blinding of others unlikely to introduce bias.

 
High risk of bias

Any one of the following.

  • No blinding or incomplete blinding, and the outcome or outcome measurement is likely to be influenced by lack of blinding.
  • Blinding of key study participants and personnel attempted, but likely that the blinding could have been broken.
  • Either participants or some key study personnel were not blinded, and the non-blinding of others likely to introduce bias.

 
Unclear

Any one of the following.

  • Insufficient information to permit judgement of low or high risk of bias.
  • The study did not address this outcome.

 

4. Were incomplete outcome data adequately addressed?

 
Low risk of bias

Any one of the following.

  • No missing outcome data.
  • Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias).
  • Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups.
  • For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate.
  • For continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size.
  • Missing data have been imputed using appropriate methods.

 
High risk of bias

Any one of the following.

  • Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups.
  • For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate.
  • For continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size.
  • ‘As-treated’ analysis done with substantial departure of the intervention received from that assigned at randomisation.
  • Potentially inappropriate application of simple imputation.

 
Unclear

Any one of the following.

  • Insufficient reporting of attrition/exclusions to permit judgement of low or high risk of bias (e.g. number randomised not stated, no reasons for missing data provided).
  • The study did not address this outcome.

 

5. Are reports of the study free of suggestion of selective outcome reporting?

 
Low risk of bias

Any of the following.

  • The study protocol is available and all of the study’s pre-specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre-specified way.
  • The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre-specified (convincing text of this nature may be uncommon).

 
High risk of bias

Any one of the following.

  • Not all of the study’s pre-specified primary outcomes have been reported.
  • One or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre-specified.
  • One or more reported primary outcomes were not pre-specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect).
  • One or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta-analysis.
  • The study report fails to include results for a key outcome that would be expected to have been reported for such a study.

 
Unclear

Insufficient information to permit judgement of low or high risk of bias. It is likely that the majority of studies will fall into this category.

 

6. Other sources of potential bias

 
Low risk of bias

The study appears to be free of other sources of bias.

 
High risk of bias

There is at least one important risk of bias. For example, the study:

  • had a potential source of bias related to the specific study design used; or
  • has been claimed to have been fraudulent; or
  • had some other problem.

 
Unclear

There may be a risk of bias, but there is either:

  • insufficient information to assess whether an important risk of bias exists; or
  • insufficient rationale or evidence that an identified problem will introduce bias.

 

Contributions of authors

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support

Thomas Pinkney conceived the review question, developed the protocol, coordinated development, completed the first draft, performed part of the writing and editing of the protocol, made an intellectual contribution, advised on the protocol, approved the final draft prior to submission and is guarantor. 
John McCall conceived the review question, developed the protocol and coordinated development, completed the first draft, performed part of the writing and editing of the protocol, made an intellectual contribution, advised on the protocol, approved the final version prior to submission. 
Jo Dumville conceived the review question, developed the protocol, completed the first draft of the protocol, performed part of the writing and editing of the protocol, made an intellectual contribution, advised on the protocol, and approved the final version prior to submission. 
Francesca Edwards conceived the review question, developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission. 
Adrian Gheorghe developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual contribution, advised on the protocol, and approved the final version prior to submission. 
David Bartlett conceived the review question, developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission. 
Melanie Calvert developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission. 
Benjamin Fletcher developed the protocol, completed the first draft, performed part of the writing and editing, made an intellectual contribution, advised on the protocol and approved the final version prior to submission.

 

Contributions of editorial base:

Nicky Cullum: edited the protocol; advised on methodology, interpretation and protocol content.
Kurinchi Gurusamy, Editor: advised on methodology and protocol content. Approved the final protocol prior to submission.
Sally Bell-Syer: coordinated the editorial process. Advised on methodology, interpretation and content. Edited and copy edited the protocol.
Ruth Foxlee: designed the search strategy and edited the search methods section.

 

Declarations of interest

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support

The authors Pinkney, Gheorghe, Bartlett, and Calvert are members of the trial management group for the ROSSINI Trial - a multicentre UK randomised controlled trial assessing the efficacy of wound-edge protection devices in the reduction of surgical site infection for adult patients undergoing laparotomy. This trial is independent research commissioned by the National Institute for Health Research (NIHR) under the Research for Patient Benefit (RfPB) programme (PB-PG-1208-18234) and is not sponsored by industry. Mr Fletcher works alongside the members of the trial management group at the University of Birmingham, but is not a member himself.

 

Sources of support

  1. Top of page
  2. Background
  3. Objectives
  4. Methods
  5. Acknowledgements
  6. Appendices
  7. Contributions of authors
  8. Declarations of interest
  9. Sources of support
 

Internal sources

  • Department of Surgical Sciences, Dunedin School of Medicine, Otago University, New Zealand.
    Salary

 

External sources

  • NIHR/Department of Health (England), (Cochrane Wounds Group), UK.

References

Additional references

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Acknowledgements
  7. Appendices
  8. Contributions of authors
  9. Declarations of interest
  10. Sources of support
  11. Additional references
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