AHRQ Methodology
QualityAdvisor uses the source code from the Agency for Healthcare Research Quality (AHRQ) SAS software module for PSIs and IQIs to calculate PSI and IQI rates. This is the standard software module from AHRQ that runs the SAS statistical software package.
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For each patient, the AHRQ SAS module accepts up to 35 ICD diagnosis codes and up to 30 ICD procedure codes. The order of the diagnosis and procedure codes is evaluated in the software based on the order in which Premier receives them.
The first diagnosis code is the principal code and the remaining 34 are the secondary codes. If a patient has any codes beyond the 35-code limit, the AHRQ SAS module won’t recognize those codes.
The first procedure code is the principal code and the remaining 29 are the secondary codes. If a patient has any codes beyond the 30-code limit, the AHRQ SAS module won’t recognize those codes.
- For both Patient Safety Indicators (PSI) and Inpatient Quality Indicators (IQI), QualityAdvisor does not consider utilization of area-level procedures, which are procedures whose use varies widely across relatively similar geographic areas (for example, CABG Area Rate).
Risk Adjustment
Risk-adjustment is a statistical process that takes into account the underlying health status related to patient outcomes or health care costs. In order to create a robust regression model, AHRQ first required two complete years of ICD-10 data beginning with 10/1/2015 discharges. Risk-adjustment is now currently available with the ICD-10 based AHRQ versions.
Data Used in Calculating PSI Rates
Reference Population for the PSIs
The reported Expected, Risk-adjusted, and Smoothed rates for the hospital-level PSIs are calculated using data from a reference population.
AHRQ uses the Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SID) as the reference population. The SID is a large database of hospital discharge data maintained by AHRQ. It contains data for all hospital discharges from 47 States, representing more than 95 percent of all U.S. hospital discharges (for more information, see http://www.hcup-us.ahrq.gov/sidoverview.jsp).
Using this dataset, AHRQ performs statistical analyses to calculate reference population PSI rates and identify risk factors. These measures are available as part of the AHRQ SAS software that Premier uses to calculate the PSI rates.
Weights for the Smoothed Rates
The Smoothed rates are calculated using weights that reflect the stability of your hospital’s PSI rates, which are affected by the size of your hospital’s patient population and the types of quality and safety events that occur in your hospital.
When Premier runs the AHRQ QI SAS software, weights are applied to the risk-adjusted rates for each PSI. These weights “shrink” the hospital’s Risk-adjusted rate toward the overall mean from the SID. The shrinkage estimate is called a “reliability adjustment.”
For a hospital with less reliable PSI rate estimates, its smoothed rates will shrink more toward the SID mean (Reference Population Rate), compared to Smoothed rates for a hospital with more reliable rates. The resulting rates will have smaller year-to-year fluctuations in performance, so they will appear “smoother” than the raw rates.