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Risk Adjustment Factors Included in the SIR
Surgical Site Infections
Colon (COLO) Procedures, Complex 30-Day Model
The number of predicted SSI events under the 2022 baseline is calculated using a logistic regression model and is risk adjusted based on the following variables found to be statistically significant predictors of SSIs. Information about the statistical properties of NHSN risk adjustment models, including how the number of predicted events is calculated, is available in NHSN’s Guide to the SIR (2022 baseline).
| Parameter | Parameter Estimate | Standard Error | P-value |
|---|---|---|---|
| Intercept | -5.5134 | 0.1039 | <.0001 |
| Scope: No | 0.6402 | 0.0271 | <.0001 |
| Scope: Yes | REFERENT | – | – |
| Procedure duration: 67-107 (Min) | 0.2344 | 0.0521 | <.0001 |
| Procedure duration: 108-145 (Min) | 0.3900 | 0.0515 | <.0001 |
| Procedure duration: 146-232 (Min) | 0.5221 | 0.0490 | <.0001 |
| Procedure duration: 233-296 (Min) | 0.6950 | 0.0556 | <.0001 |
| Procedure duration: ≥297 (Min) | 0.8690 | 0.0541 | <.0001 |
| Procedure duration: ≤66 (Min) | REFERENT | – | – |
| Trauma: Yes | 0.3607 | 0.0520 | <.0001 |
| Trauma: No | REFERENT | – | – |
| ASA score: 3/4/5 | 0.3089 | 0.0281 | <.0001 |
| ASA score: 1/2 | REFERENT | – | – |
| Patient’s age: 18-39 years | 0.5080 | 0.0532 | <.0001 |
| Patient’s age: 40-62 years | 0.3765 | 0.0443 | <.0001 |
| Patient’s age: 63-79 years | 0.1970 | 0.0438 | <.0001 |
| Patient’s age: 80-109 years | REFERENT | – | – |
| Surgical wound class: Contaminated/Dirty | 0.1707 | 0.0245 | <.0001 |
| Surgical wound class: Clean-Contaminated | REFERENT | – | – |
| Total number of beds1: ≥319 beds | 0.0958 | 0.0248 | 0.0001 |
| Total number of beds1: <319 beds | REFERENT | – | – |
| Emergency: Yes | 0.1097 | 0.0300 | 0.0003 |
| Emergency: No | REFERENT | – | – |
| Medical School Affiliation1: Major | 0.0723 | 0.0259 | 0.0052 |
| Medical School Affiliation1:
Graduate/Undergraduate/None |
REFERENT | – | – |
| Sex at birth (prior to 2025, reported as gender): Male | 0.1212 | 0.0231 | <.0001 |
| Sex at birth (prior to 2025, reported as gender): Female | REFERENT | – | – |
| BMI: ≥40 | 0.1111 | 0.0427 | 0.0093 |
| BMI: <40 | REFERENT | – | – |
| Oncology Hospital2: Yes | 0.3658 | 0.0831 | <.0001 |
| Oncology Hospital2: No | REFERENT | – | – |
| Anesthesia: Yes | 0.1708 | 0.0823 | 0.0380 |
| Anesthesia: No | REFERENT | – | – |
Footnotes:
1 Total number of beds and medical school affiliation are reported on the Annual Hospital Survey.
2 Based on NHSN enrollment as HOSP-ONC.
