Appendix A

SSI SIRs (Superficial and Deep Tissue)

The NHSN protocol defines two different definitions for SSIs: “all” and “complex” This appendix contains metrics using the “all” definition, which includes superficial, deep tissue, and organ space SSIs. For a more detailed description of the “all” case definition and adjustment models, please refer to the SIR Guide Supplement.⁴² HHS does not set a 2020 reduction goal for this classification of SSIs.

State SIRs by Surgery Type

Table A.1 shows the number of hospitals and surgeries performed and included in the analysis, number of SSIs, number of predicted infections, and respective SIRs for each surgical procedure. Note that the number of surgeries performed is slightly different than those displayed in Chapter 4, Table 12. Surgeries were excluded from this analysis if one or more risk factor variables were missing. Because the all and complex models contain different risk factors that are included in the statistical model and these risk factors have different completion rates, the number of procedures excluded differs also.

SSI SIRs for each of the seven monitored surgical procedures ranged between 0.66 and 0.97. The state-wide SSI SIR for colon surgeries was statistically significantly lower than the 2015 national baseline (SIR: 0.67, 95% CI:(0.61, 0.73)). The state-wide SSIs SIR for abdominal hysterectomy surgeries was also statistically significantly lower than the 2015 national baseline (SIR: 0.66, 95% CI: (0.56, 0.79)).The state-wide SIRs for hip replacement, cardiac surgery and CBG with two incisions were close to 1.0 and not statistically significant (SIR: 0.97, SIR: 0.95, SIR: 0.93 respectively), whereas SIRs for knee replacement and CBG with one incision surgeries were each less than 1.0 and not statistically significant (Knee replacement SIR: 0.9, CBG with one incisions SIR: 0.8).

Table A1: Superficial, Deep Tissue and Organ Space SSI SIRs for each of seven Procedures | Pennsylvania, 2018

5.0.1 Hospital Type

Because nearly all surgical procedures were performed in ACHs, calculation of SSI SIRs stratification by hospital type is limited. Only six surgical types and hospital type pairs had more than 1.0 predicted SSI, and these are presented in Table A.2 below.

The SIRs for colon surgeries performed in critical access hospitals was statistically significantly more than the 2015 national baseline (SIR: 3.51 SIR: 95% (1.63, 6.66)). The SIR for knee and hip replacement surgeries performed in critical access hospitals was also above 1.0, but not statistically significantly different (SIR for knee replacement: 1.17, SIR for hip replacement: 1.69). Colon surgeries performed at children’s hospitals and abdominal hysterectomies performed at critical access hospitals resulted in 6.1 and 2 fewer SSIs than were predicted (colon SIR 0.45, abdominal hysterectomy SIR: 0.34).

Table A2: SIRs from Surgical-Procedure Combinations Commonly Performed in Specific Hospital Types | Pennsylvania, 2018

5.0.2 Distribution

The distribution of 2018 and 2017-2018 SIRs for the seven surgery types is presented in Figure A.1. The SIR was calculated in those hospitals in which the predicted number of infections was 1.0 or more for either timeframe, resulting in the inclusion of 525 hospital-procedure pairs. This includes only 4 hospital surgery pairs from children’s hospitals and 1 from CAHs. The remaining SIRs are from ACHs.

Figure A.1: Distribution of SSI SIRs Stratified by Surgical Procedure Type| Pennsylvania, 2017-2018 and 2018

5.0.3 Statistically Significant SIRs

Table A.3 shows the number of hospitals with statistically significant SSIs. It is noteworthy that 17 hospitals that performed colon surgeries had statistically significant lower SIRs compared with the 2015 national benchmark. More hospitals that performed hip replacement, knee replacement, and abdominal hysterectomy procedures had statistically significant SIRs greater than 1.0 than statistically significant SIRs less than 1.0.

Table A.3: Number of Hospitals with Statistically Significant SSI SIRs | Pennsylvania 2017-2018 and 2018

5.0.4 Hospital List

Table A.4 displays the comprehensive list of all hospital-surgical procedure pairs in which one or more of the surgeries were performed (N = 788). The SIR was calculated for 318 hospitals surgery pairs (40%) when the predicted number of infections was greater than 1.0 in 2018. An additional 80 SIRs (10%) could be calculated when 2017 and 2018 data were combined.

The remaining 390 hospital surgery pairs (49%) had less than one predicted infection; therefore, SIRs could not be calculated. In 86 (22%) of those pairs, one or more SSIs occurred even though less than 1.0 was predicted.

Table A.4: Hospitals that Perform Seven Types of Surgeries and their SSI SIRs and Associated Measures | Pennsylvania, 2017-2018 and 2018

Hospitals printed in red have statistically significantly more SSIs than predicted. Hospitals printed in blue have statistically significantly fewer SSIs than predicted.