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Table 1 The association between selected risk factors and surgical site infections

From: Risk of surgical site infection and efficacy of antibiotic prophylaxis: a cohort study of appendectomy patients in Thailand

Risk factors N Infection Rate* Relative risk
     Crude 95% CI Adjusted** 95% CI
Duration of antibiotic prophylaxis        
   None 167 5 3.0 1.00 Reference 1.00 Reference
   1 day 1159 12 1.0 0.34 0.12–0.97 0.30 0.10–0.89
   >1 day 813 9 1.1 0.36 0.12–1.09 0.29 0.09–0.92
Duration of operation        
   ≤ 1.0 hour 1738 16 0.9 1.00 Reference 1.00 Reference
   >1.0 hour 401 10 2.5 2.75 1.24–6.11 3.29 1.44–7.52
Age        
   1–20 years 808 6 0.7 1.00 Reference 1.00 Reference
   21–40 years 853 14 1.6 2.23 0.85–5.83 2.15 0.82–5.68
   41–60 years 382 5 1.3 1.77 0.54–5.85 1.91 0.57–6.48
   >60 years 96 1 1.0 1.41 0.17–11.81 2.11 0.22–20.76
Type of operation        
   Elective 591 9 1.5 1.00 Reference 1.00 Reference
   Emergency 1548 17 1.1 0.72 0.32–1.62 0.78 0.33–1.83
Total 2139 26 1.2 - - - -
  1. * Rate = # infections/100 operations
  2. **Adjusted for sex, age, length of preoperative stay, type of operation, ASA score, and duration of operation