Perioperative antibiotic prophylaxis in adults - Sistema Nazionale ...

(1-expected baseline risk) x expected baseline risk x (1-odds ratio)§ expected baseline risk = % of ISS in the hospital§§ Odds ratio = ratio between the odds of an event occurring in the treated group andthe odds of the same event occurring in a control group (an odds ratio of 1 means thatthere is no difference between the groups).Wherever possible, the odds ratio and NNTs shown in Table 6 were derived from themost recently published meta-analyses. In some cases, however, data from differenttrials were pooled and no formal meta-analysis was performed.The NNT is only one of the elements necessary to estimate the cost-benefit ratio.Additional information is needed to evaluate the clinical consequences of theoutcome (specifically, a wound infection or SSI) measured in the trial(s) and used tocalculate the NNT.For example, the NNT derived from studies of implants of hip prostheses is muchhigher than that derived from studies of transvaginal hysterectomy: 30 patients needto be treated to prevent one case of infection associated with hip prosthesis implant,while 4 patients need to be treated with antibiotic prophylaxis to prevent one episodeof infection following transvaginal hysterectomy (see Table 6). It should nonethelessbe borne in mind that whereas an infection following arthroprosthesis implant is asevere complication that almost certainly calls for repeat surgery 61 , the febrilecomplication following transvaginal hysterectomy has no clinically relevantconsequences in most cases 62 .Indications for perioperative antibiotic prophylaxisTable 6 lists both operations for which systematic reviews or methodologicallycorrect RCTs are available that compare the efficacy of prophylaxis with a placeboand those for which direct evidence is lacking but which the panel decided to includeon account of their impact in current practice (grey areas).