primary outcome:
Preoperative hair removal to reduce surgical site infection
The primary outcome was the proportion of participants who developed SSIs. We accepted the authors' definitions of an SSI. Where SSIs were reported at several different time points, we recorded and used the time closest to 30 days (Centers for Disease Control and Prevention (CDC) definition of an SSI).All three studies reported surgical site infection as an outcome. Infections were measured at four weeks (Abouzari 2009), "follow up" or at 30 days (Kowalski 2016), or no details were given (Lu 2002). Results are presented as risk ratio (RR), where the risk ratio is the risk of infection in the clipping group divided by the risk of infection in the no hair removal group. A risk ratio of less than one indicates fewer infections in the clipping group. We pooled all trials using a random‐effects model. There may be little difference in the risk of SSI when hair is removed by clippers compared with no hair removal (RR 0.95, 95% confidence interval (CI) 0.65 to 1.39; 3 trials, n = 1733) (Analysis 1.1). This corresponds to an absolute effect of 3 fewer surgical site infections per 1000 people in the clipping group (95% CIs 21 fewer infections to 23 more infections per 1000 people). The evidence is of low certainty, downgraded twice for very serious imprecision (summary of findings Table 1). We carried out a sensitivity analysis to exclude any QRCTs (Lu 2002), or studies at high risk of bias from the meta‐analysis. This showed no change in effect, resulting in a pooled RR of 0.97 (95% CI 0.66 to 1.42; 2 trials, n = 1673) (Analysis 1.2). The certainty of evidence for the sensitivity analysis is low, downgraded twice for very serious imprecision due to wide confidence intervals and a relatively small number of events.All eight studies reported surgical site infection as an outcome; however, Ilankovan 1992 did not provide any raw data and is reported separately as a narrative. We pooled the remaining seven studies in a meta‐analysis with 1706 participants. Infections in the seven studies were measured at 7 to 10 days (Rojanapirom 1992), discharge or 8 to 10 days (Nascimento 1991), 28 days (Court‐Brown 1981), 30 days (Abouzari 2009; Kattipattanapong 2013), and 1 and 3 months (Celik 2007). Sun 2014 did not state when infections were assessed. Results are presented as risk ratio (RR), where the risk ratio is the risk of infection in the shaving group divided by the risk of infection in the no hair removal group. A risk ratio of more than one indicates more risk of infection in the shaving (with a razor) group. We pooled all trials using a random‐effects model. The evidence shows the risk of surgical site infection is probably increased in people who have hair removed with a razor compared with no hair removal (RR 1.82, 95% CI 1.05 to 3.14; 7 trials, n = 1706) (Analysis 2.1). This corresponds to an absolute increase in surgical site infections in the razor group of 17 more surgical site infections per 1000 (95% CIs 1 more to 45 more infections per 1000 people). The evidence is of moderate certainty, downgraded once for serious imprecision (summary of findings Table 2). We carried out a sensitivity analysis to exclude any QRCTs or other studies at high risk of bias, Celik 2007, from the meta‐analysis. In this sensitivity analysis the confidence intervals were wider and included no effect and the possibility of harm; pooled RR of 1.71 (95% CI 0.97 to 3.01; 6 trials, n = 917) (Analysis 2.2). The certainty of evidence for the sensitivity analysis is moderate, downgraded once for serious imprecision. Ilankovan 1992 included 50 participants and reported no difference in the incidence of infection between groups.One study reported surgical site infection as an outcome (Court‐Brown 1981). Court‐Brown 1981 included 267 randomised participants, and infections were measured at 28 days. Results are presented as risk ratio (RR), where the risk ratio is the risk of infection in the depilation group divided by the risk of infection in the no hair removal group. A risk ratio of more than one indicates more infections in the depilation group. The evidence shows there may be little difference in surgical site infections when hair is removed with a depilatory cream or is not removed (RR 1.02, 95% CI 0.45 to 2.31; 1 trial, n = 267) (Analysis 3.1). This corresponds to an absolute increase in surgical site infections in the cream group of 2 more infections per 1000 people (95% CIs 43 fewer infections to 102 more infections per 1000 people). The evidence is of low certainty, downgraded twice for very serious imprecision (summary of findings Table 3).All seven studies reported surgical site infection as an outcome. Infections were assessed at two weeks (Balthazar 1983; Taylor 2005), 30 days (Abouzari 2009; Alexander 1983; Ko 1992), and three months (Domes 2011; Grober 2013). Results are presented as risk ratio (RR), where the risk ratio is the risk of infection in the shaving with razor group divided by the risk of infection in the clipping group. A risk ratio of more than one indicates more infections in the shaving (with a razor) group. We pooled all trials using a random‐effects model. The evidence shows the risk of surgical site infection is probably higher in participants who had hair removed with a razor compared with those who had hair removed with clippers (RR 1.64, 95% CI 1.16 to 2.33; 7 trials, n = 3723) (Analysis 4.1). The evidence is of moderate certainty, downgraded once for serious risk of bias (summary of findings Table 4). This corresponds to an absolute increase in surgical site infection risk in the razor group of 16 more surgical site infections per 1000 people (95% CIs 4 more to 33 more infections per 1000 people). We carried out a sensitivity analysis to exclude any QRCTs or studies at high risk of bias, as well as studies on scrotal hair from the meta‐analysis (Domes 2011; Grober 2013; Ko 1992). This demonstrated no change in effect, resulting in a pooled RR of 1.55 (95% CI 1.07 to 2.25; 4 trials, n = 1457) (Analysis 4.2). The certainty of evidence for the sensitivity analysis is moderate, downgraded once for serious imprecision.We conducted a post hoc subgroup analysis to address the concern that clippers are not suited to hair removal from male genitalia because of the possibility of catching skin folds in the clipper (Morey 2013). Results from two studies comparing hair removal from male scrotums showed that it is unclear whether there is a difference in risk of surgical site infection when hair was removed with razors or clippers (RR 0.99, 95% CI 0.14 to 6.91; 2 trials, n = 280) (Analysis 4.1) (Domes 2011; Grober 2013). The evidence is of very low certainty, downgraded once for serious risk of bias and twice for serious imprecision.Nine studies reported surgical site infection as an outcome assessed at 10 days (Thorup 1985), 28 days (Court‐Brown 1981), five weeks (Adisa 2011), six weeks (Suvera 2013), weekly review (Seropian 1971), and at discharge and outpatient visit (Breiting 1981). Thur de Koos 1983 did not state when infections were assessed. One study stated that they would report surgical site infections (Karegoudar 2012); however, as no details were provided, it was not possible to present this study as a narrative or in a meta‐analysis. We combined the remaining nine studies in a meta‐analysis, and presented results as risk ratio (RR), where the risk ratio is the risk of infection in the shaving group divided by the risk of infection in the depilatory cream group. A risk ratio of more than one indicates more infections in the shaving with a razor group. We pooled all trials using a random‐effects model. The risk of surgical site infections is probably higher in participants who have hair removed by shaving with a razor compared with removal by depilatory cream (RR 2.28, 95% CI 1.12 to 4.65; 9 trials, n = 1593) (Analysis 5.1). This corresponds to an absolute increase in surgical site infection of 46 more SSIs per 1000 people in the razor group (95% CI 4 to 131 more infections per 1000 people). The evidence is of moderate certainty, downgraded once for serious risk of bias (summary of findings Table 5). The direction of the evidence was the same in a sensitivity analysis excluding QRCTs and studies at high risk of bias (RR 2.80, 95% CI 1.22 to 6.46; 5 trials, n = 790) (Analysis 5.2). The certainty of evidence for the sensitivity analysis is moderate, downgraded once for serious imprecision.Alexander 1983 reported surgical site infection as an outcome. Infections were assessed 30 days after discharge. The results are presented as risk ratio (RR), where the risk ratio is the risk of infection from removing hair the day before surgery is divided by the risk of infection from removing hair the day of surgery. A risk ratio of less than one indicates fewer infections when removing hair the day of surgery. There may be a small reduction in surgical site infections when hair is removed on the day of surgery compared with the day before surgery (RR 0.83, 95% CI 0.54 to 1.30; 1 trial, n = 977) (Analysis 6.1). This corresponds to an absolute decrease in surgical site infection risk of 12 fewer infections per 1000 people on the day of removal group (95% CI 32 fewer to 20 more infections per 1000 people). The evidence is of low certainty, downgraded once for serious imprecision and once for inconsistency given the different types of hair removal approaches used (summary of findings Table 6). Subgroup analysis for hair removal with either razors or clippers showed some heterogeneity in findings.