None of the authors has any disclosures or conflicts of interest to report

None of the authors has any disclosures or conflicts of interest to report

The Effect OF PATOS (Present At the Time Of Surgery) On The Calculation of SSI Rates for Appendectomy and Colectomy: Is PATOS a Useful Concept? Albert W Dibbins, MD, FACS David E Clark, MD, MS,FACS Robert Cormier, BSN Department of Surgery Maine Medical Center Portland, Maine

Effect of Assigning PATOS 1. An assigned postoperative wound or organ space infection is not counted 2. It does not appear in the hospital s Select Postoperative Occurrence Summary 3. It does not appear in the hospital s Semi Annual Report (SAR) 4. It is retained in the hospital s NSQIP database and is retrievable using the Data Download tool

Methods Adult NSQIP Participant User Files (PUF) from 2009 2012 were examined to estimate the effect of pre-operative perforation and the effect of assigning PATOS on the rates of Surgical Site Infection for Appendectomies (91,029 cases, open and laparoscopic) and Colectomies (105,553 cases, open and laparoscopic) Cases were determined to have definite preoperative infection if the CPT or ICD-9 code specified intestinal perforation, peritonitis, or abscess. For all years, rates of surgical site infection were calculated comparing cases with and without definite preoperative infection. For 2011 and 2012 data, the rates of superficial, deep, and organ space infection were calculated comparing results before and after excluding PATOS cases. Statistical significance for comparisons was determined using Pearson chi-square analysis.

Effect of Intestinal Perforation/Abscess on Rates of SSI (Percent) Appendectomy RR 3.57 95%CI 3.12 4.08 Any WI SWI DWI OSI Year No Preoperative Infection 2009 2.33 1.26 0.18 0.94 2010 2.34 1.30 0.20 0.94 2011 1.79 0.81 0.14 0.86 2012 2.19 1.04 0.16 0.99 Preoperative Infection 2009 8.60 2.71 1.19 4.87 2010 7.46 1.66 0.70 5.25 2011 7.82 1.44 0.72 5.88 2012 7.82 1.77 0.72 5.56

Effect of Intestinal Perforation/Abscess on Rates of SSI (Percent) Colectomy RR 1.38 95%CI 1.29 1.48 Any WI SWI DWI OSI Year Preoperative Infection No 2009 13.08 7.90 1.49 4.14 2010 12.23 7.40 1.30 3.93 2011 12.37 6.90 1.43 4.44 2012 12.19 7.23 1.42 4.42 Preoperative Infection 2009 16.38 7.27 2.17 8.08 2010 16.32 7.83 1.88 6.73 2011 16.85 4.81 3.15 9.35 2012 18.89 5.93 3.10 10.31

Effect of PATOS on Rates of Wound Infection (Percent) Appendectomy For 2012, RR 0.88 95%CI 0.55 0.68 Any WI SWI DWI OSI Year Not Adjusted for PATOS 2009 3.36 1.50 0.35 1.58 2010 3.17 1.35 0.28 1.60 2011 2.81 0.91 0.24 1.70 2012 3.13 1.17 0.25 1.76 Adjusted for PATOS 2009 2010 2011 1.73 0.76 0.17 0.81 2012 1.92 1.07 0.15 0.73

Effect of PATOS on Rates of Wound Infection (percent) Colectomy For 2012, RR 0.88 95%CI 0.84-0.92 Any WI SWI DWI OSI Year Not Adjusted for PATOS 2009 13.21 7.88 1.52 4.30 2010 12.39 7.42 1.33 4.04 2011 12.55 6.84 1.47 4.63 2012 12.41 6.77 1.48 4.62 Adjusted for PATOS 2009 2010 2011 10.97 6.44 1.27 3.51 2012 10.91 6.52 1.30 3.43

PATOS Definitions for Surgical Site Infections Superficial Incisional SSI - PATOS Evidence or suspicion of a superficial infection found at the intended surgical site. This must be noted preoperatively or found intra-operatively at the surgical site and may include an open wound, cellulitis (erythema, tenderness AND swelling), or wound infection. Deep Incisional SSI PATOS Evidence or suspicion of a deep infection (e.g., muscle and fascia layers) found at the intended surgical site. This must be noted preoperatively or found intra-operatively at the surgical site and may include an open wound, cellulitis (erythema, tenderness AND swelling), or wound infection. Organ Space SSI PATOS Evidence or suspicion of an abscess or other infection involving the organ or space manipulated during the operation. This must be noted preoperatively or found intra-operatively in the surgical space

PATOS Misclassification Assigning YES to SWI and DWI Assigning NO to OSI Appendectomy SWI - 133 cases 38 assigned YES = 29% misclassified DWI - 59 cases 28 assigned YES = 47% misclassified OSI - 469 cases 118 assigned NO = 25% misclassified Colectomy SWI - 117 cases 24 assigned YES = 21% misclassified DWI - 68 cases 29 assigned YES = 42% misclassified OSI - 214 cases 63 assigned NO = 29% misclassified

Conclusions Is PATOS a useful concept? NO! Reporting all Surgical Site Infections stratified by the presence or absence of preoperative infection would provide better data to the individual sites and would not obscure important results Although the total number of misclassifications is small, it appears that further education in the proper assigning of the PATOS variables would improve the data which is acquired

NHSN SSI Reporting If a patient has an infection in the organ space being operated on, subsequent continuation of this infection type during the remainder of the surveillance period is considered an organ space SSI, if organ space SSI and site-specific infection criteria are met.