About our quality performance

There are several national organizations that define the best ways to measure quality. These organizations use research and expert consensus to decide what data to gather, how to analyze it and how to display the data. They set the standards to ensure that any participating hospital has reliable and accurate data. Some measures are very straightforward and objective, and some collect subjective data such as patient opinions.

In an effort to be transparent in our quality data reporting, we choose reliable national measures and then we report our data even if the results show that we need to improve. We share all the data with you, even if we are not yet meeting our performance goals on the measures.

Our quality measures were chosen because they meet these goals:

  • Transparency – we want measures to be upfront and easy to understand
  • Public methodology – the methods of collecting and analyzing data are available for study
  • Validity – we want measures to be validated by reputable research or expertise   
  • Comparisons – we want measures that can be compared to a national average or other comparison or benchmark so consumers can compare us with the high standards set for hospitals across the nation
  • Expertise – we choose measures that have been developed and tested by the most well-respected, independent national experts
  • Relevance – we choose measures that are relevant to our patients, to help you to understand, select  and plan for high quality healthcare

We display information in a way that is understandable and useful to you.  We share our results consistently over time; if our performance is not as high as we’d like, we show you the data anyway, while we work on improvement. 

How we measure quality

At Northwestern, we describe quality simply as Delivering Exceptional Care - care that is effective, timely, safe, courteous and convenient. Hospitals measure quality in two ways:

·         Treatments and Procedures

·         Outcomes

Treatments and Procedures - This type of quality measure is used to assess whether hospitals are using the right treatments and procedures when patients are in the hospital. We choose measures that are valid and reliable and focus on those that can be compared with data from government and other national organizations.

An example of a treatment and procedure measure is:

The percentage of patients who receive “dual” radiology scans. The National Centers for Medicare and Medicaid Services collect data on this measure because studies have shown that patients who receive two scans (with and without contrast medicine) are receiving increased radiation exposure.  Ideally, the dual scans should be avoided when the patient’s care does not require both.  This measure does not tell you whether the scans were medically appropriate.

Outcomes - This type of measure assesses the success of the treatments and procedures patients receive in the hospital. However, outcomes are very difficult to measure and statistically analyze successfully and equally because every patient is different.

For example, an otherwise healthy 23-year-old patient who has pneumonia will not have the same chance of survival as a 93-year-old patient with underlying heart disease or other conditions. Because of these sometimes vast differences, there are not many valid and reliable outcome measures available.

A few leading independent national measurement agencies have developed statistical methods to adjust for severity of patient illness when predicting outcomes, such as risk of mortality and complications. These models aren’t perfect and should not be the sole deciding factor when choosing a healthcare provider or hospital, but we have included relevant outcome measures adopted by these leading agencies in our Quality Rating.

Examples of outcome measures are:

How many patients who arrive at the hospital with a heart attack survive to discharge, or as long as 30 days after going home?  This is measured by the federal Centers for Medicare and Medicaid Services. Heart attacks are a common cause of death, but when heart attack patients quickly receive the right care, their chance of survival increases. Treatments and procedures at a hospital can have an effect on heart attack survival, so this measure may be an indicator of the quality of care a hospital provides. 

How many patients develop an infection after surgery? This is measured by the American College of Surgeons’ National Surgical Quality Improvement Program. Surgical infections can cause pain, and in some cases, they cause significant harm to patients. Because most surgical infections are preventable, post-surgical infection rates are important quality measures.


Learn more about data collection, data validation and the reporting process.


We want to know what you think. If there are aspects of care that we are not measuring, or you find measures you think should be updated, we want to hear your ideas. Please don't hesitate to send us an e-mail.


In this quality report, we (Northwestern Memorial Hospital) have listed our performance ratings and scores on numerous quality indicators and metrics. When available, we’ve included performance data from outside sources for comparison, such as the Illinois or United States benchmark.

While we have attempted to ensure the accuracy of the data we report, we make no representations or warranties, expressed or implied, as to the accuracy or completeness of the information reported. Likewise, we make no representations or warranties, expressed or implied, as to the accuracy of the comparative data. We assume no legal liability or responsibility for any errors or omissions in the information or for any loss or damage resulting from the use of any information contained in our Quality Performance or quality website. 

Links to other sites are not endorsements of any site, and we do not have any control over or responsibility for the content of these sites.  If you link to other sites, you do so at your own risk.  Likewise, any references to other organizations do not imply an endorsement by those organizations of Northwestern Memorial Hospital’s services or analyses.