6 Appendix

6.0.1 SSI SIRs (Superficial and Deep Tissue)

As mentioned in the methods chapter of this report, the NHSN protocol sets forth two different methods to evaluate SSIs, which are referred to as “all” and “complex”. Results presented in this section contain metrics using the “all” model, which includes superficial infections, 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 Supplement⁴⁶. HHS does not set a 2020 reduction goal for this classification of SSIs

6.0.2 State SSI SIRs by Type of Surgical Procedure

Table A.1 shows the number of surgeries performed in 2019, number of SSIs, number of predicted infections and respective SIR values for each surgical procedure. Note that the number of predicted surgeries performed is slightly different than those displayed in Chapter 4, Table 12 but the number of surgeries performed is identical.

The state SSI SIR for the seven monitored surgical procedures ranges between 0.63 and 1.01. The SIR for hip replacement is close to 1.0 (SIR: 1.01) and not statistically different than the 2015 national baseline. The SIR for CBG with 1 incision is also not statistically different than the 2015 national baseline, but was 30.7% better than predicted (SIR: 0.69). The state-wide SSI SIR values for colon surgeries, knee replacement, abdominal hysterectomies, cardiac and CBG with 2 incisions are statistically significantly lower than the 2015 national baseline (Colon: SIR: 0.7, 95% CI: (0.65, 0.76), knee replacement: SIR: 0.83, 95% CI: (0.72, 0.95), cardiac: SIR: 0.72, 95% CI: (0.52, 0.98), CBG with 2 incisions SIR: 0.68, 95% CI: (0.54, 0.84), abdominal hysterectomy: SIR: 0.63, 95% CI: (0.53, 0.74))

Table A1: SSI SIRs for each of seven procedures | Pennsylvania, 2019

6.0.3 Hospital Type

Because nearly all surgical procedures were performed in acute care hospitals, calculation of 2019 SSI SIR values stratified by hospital type is limited. Six surgical procedure-hospital pairs had more than one predicted SSIs and these are presented in Table A2 below.

The SIR values for colon and hip replacement surgeries performed in critical access hospitals are above 1.0, but not statistically significantly different from the 2015 national baseline (Colon SIR: 1.53, 95% CI: (0.39, 4.18), Hip replacement: SIR: 1.15, 95% CI: (0.19, 3.80)). Critical access hospitals that performed knee replacement and and abdominal hysterectomy surgeries have no SSIs although two were predicted in each. Colon and cardiac surgeries performed in children’s hospitals had four and five fewer SSIs respectively that were predicted by the 2015 national baseline.

Table A2: SIRs from Surgical-Procedure Combinations Commonly Performed in Specific Hospital Types | Pennsylvania, 2019

6.0.4 Distribution

The distribution of 2019 and 2018-2019 SIR values 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 510 hospital-procedure pairs. This includes only four hospital-surgery pairs from children’s hospitals and five from CAHs. The remaining SIR values are from ACHs. Thirty-four (6.7%) of the SIR values were 2.0 or larger.

Figure A.1: Distribution of SSI SIRs Stratified by Surgical Procedure Type| Pennsylvania, 2018-2019 and 2019

6.0.5 Statistically Significant SIRs

Table A.3 shows the number of hospitals with statistically significant SSI SIR values for each type of surgical procedure. It is noteworthy that 20 hospitals that performed colon surgeries and seven hospitals that performed an abdominal hysterectomy had statistically significant lower SIR values compared with the 2015 national benchmark. Four hospitals that performed knee replacement had statistically significant SIR values more than 1.0. Two hospitals that performed knee replacement had statistically significant SIR values less than 1.0.

Table A.3: Number of Hospitals with Statistically Significant SSI SIRs | Pennsylvania 2018-2019 and 2019

6.0.6 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 = 771). The SIR was calculated for 321 hospital-surgery pairs (42%) when the predicted number of infections was greater than 1.0 in 2019. An additional 81 SIR values (11%) could be calculated when 2018 and 2019 data were combined.

The remaining 369 hospital-surgery pairs (48%) had less than one predicted infection; therefore, a SIR value could not be calculated. In 80 (22%) of those pairs, one or more SSIs were reported 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, 2018-2019 and 2019

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