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Risk Adjustment Factors Included in the SIR
MRSA Bacteremia LabID
MRSA Bacteremia LabID Event Risk Adjustment (ACHs)
The number of predicted MRSA bacteremia LabID events under the 2022 baseline is calculated using a negative binomial regression model and is risk adjusted based on the following variables found to be statistically significant predictors of MRSA bacteremia incidence. 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 | -11.6685 | 0.1598 | <0.0001 |
| Outpatient CO prevalence rate1: ≥0.085 per 100 encounters | 0.6112 | 0.0483 | <0.0001 |
| Outpatient CO prevalence rate1: 0.064 – 0.084 per 100 encounters | 0.4703 | 0.0492 | <0.0001 |
| Outpatient CO prevalence rate1: 0.040 – 0.063 per 100 encounters | 0.3537 | 0.0448 | <0.0001 |
| Outpatient CO prevalence rate1: 0.013 – 0.039 per 100 encounters | 0.2471 | 0.0437 | <0.0001 |
| Outpatient CO prevalence rate1: <0.013 per 100 encounters or no applicable locations | REFERENT | – | – |
| Inpatient CO prevalence rate2: ≥0.071 per 100 admissions | 0.3538 | 0.0343 | <0.0001 |
| Inpatient CO prevalence rate2: 0.042-0.070 per 100 admissions | 0.2238 | 0.0374 | <0.0001 |
| Inpatient CO prevalence rate2: >0 and <0.041 per 100 admissions | 0.1259 | 0.0336 | 0.0002 |
| Inpatient CO prevalence rate2: 0 per 100 admissions | REFERENT | – | – |
| Average length of stay3: ≥5.2 days | 0.7650 | 0.1211 | <0.0001 |
| Average length of stay3: 4.8-5.1 days | 0.6104 | 0.1238 | <0.0001 |
| Average length of stay3: 2.6-4.7 days | 0.5149 | 0.1210 | <0.0001 |
| Average length of stay3: 1-2.5 days | REFERENT | – | – |
| Proportion of total beds that are ICU3: ≥0.232 | 0.4254 | 0.0714 | <0.0001 |
| Proportion of total beds that are ICU3: 0.161-0.231 | 0.2758 | 0.0685 | <0.0001 |
| Proportion of total beds that are ICU3: 0.061-0.160 | 0.1856 | 0.0667 | 0.0054 |
| Proportion of total beds that are ICU3: 0-0.060 | REFERENT | – | – |
| Total number of beds3: ≥67 | 0.2204 | 0.0783 | 0.0049 |
| Total number of beds3: 1-66 | REFERENT | – | – |
| Medical school affiliation3: Major | 0.1188 | 0.0264 | <0.0001 |
| Medical school affiliation3: Graduate/Undergraduate/Non-teaching | REFERENT | – | – |
| Facility type (based on NHSN enrollment): General Acute Care Hospital (HOSP-GEN), Oncology Hospital (HOSP-ONC) | 0.2477 | 0.0799 | 0.0019 |
| Facility type (based on NHSN enrollment): Children’s Hospital (HOSP-CHLD), Military Hospital (HOSP-MIL), Orthopedic Hospital (HOSP-ORTHO), Surgical Hospital (HOSP-SURG), Women’s Hospital (HOSP-WOM), Women’s and Children’s Hospital, (HOSP-WOMCHILD) | REFERENT | – | – |
Footnotes:
1 The outpatient community-onset (CO) prevalence rate combines MRSA bacteremia data from all EDs and/or 24-hour observation units into a single, de-duplicated prevalence rate. This rate is calculated as the # of unique community-onset MRSA blood events that occurred in an ED or 24-hour observation unit / total encounters * 100. (i.e., MRSA_EDOBSprevCount / numTotencounters * 100). The prevalence rate for the entire quarter is used in risk adjustment. If the facility does not have an ED or 24-hour observation location that meets the NHSN location definition and thus are not reporting MRSA bacteremia data from these locations, the number of predicted events will be risk adjusted using the referent level of this variable.
2 Inpatient community-onset (CO) prevalence is calculated as the # of inpatient CO de-duplicated MRSA blood events, divided by total admissions x 100. (i.e., MRSA_admPrevBldCount / numadms * 100). The prevalence rate for the entire quarter is used in risk adjustment. Unrounded values truly greater than 0 are receiving the correct risk adjustment using the appropriate parameter category for values greater than 0.
3 Total number of beds and medical school affiliation are reported on the Annual Hospital Survey. Average length of stay is calculated as: total # of annual patient days / total # of annual admissions, as reported on the Annual Hospital Survey. Proportion of beds that are ICU is calculated as: # of ICU beds / total # of beds, as reported on the Annual Hospital Survey.
