Adjusted Ranking Metric (ARM)

• The Adjusted Ranking Metric (ARM) is a measure available for Acute Care Hospitals (ACHs).
• The ARM accounts for differences in volume of exposure (specifically denominator) between facilities and is preferable for ranking facilities.
• Annual, facility-specific Reliability-Adjusted Rankings based on the ARM are displayed as percentiles on the Reliability-Adjusted Ranking dashboard within the National Healthcare Safety Network (NHSN).
• A lower ranking percentile is better. For example: if your ranking is 9, your facility is doing better than 91% of facilities after accounting for overall exposure.

• Reliability-Adjusted Rankings for Central Line-associated Bloodstream Infection (CLABSI), Catheter-Associated Urinary Tract Infection (CAUTI), Methicillin-resistant Staphylococcus aureus (MRSA), Clostridioides difficile Infection (CDI), Surgical Site Infection – Colon surgery (SSI-COLO) and Surgical Site Infection – Abdominal hysterectomy (SSI-HYST) will be displayed only for acute care hospitals at this time.

The ARM provides complementary information to NHSN’s primary summary measure, the Standardized Infection Ratio (SIR). The ARM and SIR are separate measures that serve different purposes in healthcare-associated infection (HAI) analysis.

The ARM is calculated as a ratio of numerator divided by denominator, where the ARM denominator is identical to that of the SIR. Explicitly, the ARM is the reliability-adjusted number of events divided by the risk-adjusted predicted number of events, whereas the SIR is the number of events divided by the risk-adjusted predicted number of events.

Reliability-Adjustment

The type of reliability-adjustment incorporated into the ARM relies on methodological concepts dating back to 1977 and, more specifically, has been used in CMS performance measurement since 2007 (e.g., hospital 30-day mortality following acute myocardial infarction). Furthermore, the need for reliability-adjustment in assessing hospital performance has been recommended in a white paper published by a Committee of Presidents of Statistical Societies commissioned and published by CMS (https://www.cms.gov/Medicare/Quality-Initiatives-Patient-Assessment-Instruments/HospitalQualityInits/Downloads/Statistical-Issues-in-Assessing-Hospital-Performance.pdf [PDF – 694 KB]).

Calculation of ARM Scores

NHSN calculates ARM scores from all acute care hospitals for six HAIs (CLABSI, CAUTI, MRSA, CDI, SSI-COLO, SSI-HYST). Individual hospitals are ranked against all other acute care hospitals for the same year. The ARM is presented as a percentile, called the Reliability-Adjusted Ranking and is available to hospitals within the NHSN application.

Facilities with zero events and ARM Score

Facilities with zero events for a specific HAI may still receive an ARM. The ARM numerator adjusts for the volume of exposure between facilities such that facilities with lower exposure are shifted toward the mean. For ranking purposes, a facility with lower exposure or reliability will have their “zero” SIR (zero events) shifted toward the center of the distribution, and thus, be less distinguishable from the “middle of the pack.” Therefore, for a facility with low exposure (relative to all other facilities) that reported zero events, the ARM model shifts the numerator toward the mean such that the adjusted number of events is greater than zero.

Another way to look at this is to consider two separate sets of fictitious facility scenarios:

1) First, facilities A and B both have zero CLABSI SIRs, yet facility A has 1,000 central line days and facility B has 10,000 central line days. These facilities’ SIRs would be ranked at the same lowest end on a percentile distribution and would be considered the same, despite facility B having a more reliable estimate due to the larger volume of central line days (exposure). So, facility A would be shifted more toward the center of the distribution than facility B. Thus, the ARM therefore ranks the facility with a more reliable zero-estimate higher than the facility with the less reliable zero-estimate. This ranking is further presented as a percentile, where a lower score is better.

2) Suppose a second set of facilities C and D both have the same high CLABSI SIR with facility C having 1,000 central line days and facility D having 10,000 central line days. Again, facility C has less reliability than facility D. Therefore, facility C would be shifted further downward toward the center of the distribution since it has lower exposure and reliability compared to facility D.

Facilities with No ARM Score

Facilities predicted to have fewer than one event in five years (based on the expected number of events for that HAI) are currently not given an ARM for that HAI because this suggests that the facility should have zero events in the current year. Instead, the number of events for that year is shown.

Beginning in June 2025, the “Reliability-Adjusted Ranking” dashboard will be available for ACHs. This release will include data for 2022 and 2023, with additional years added in future releases. Reliability-adjusted rankings for six HAIs (CLABSI, CAUTI, MRSA, CDI, SSI-COLO, SSI-HYST) will be displayed in a bar graph (example below). During this initial release, the rankings are available for use by ACHs only and are not made available to groups within NHSN, nor used by CMS pay-for-reporting or pay-for- performance programs.

ACHs are encouraged to review their reliability-adjusted rankings.