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 - Northwestern Memorial Hospital - Chicago


The Northwestern Memorial Quality Rating includes measures from a variety of national sources that meet the following criteria:

  • Patient-Centered: relevant to patient/consumer decision making and evaluation of care
  • Valid: using professionally accepted validation and reliability evaluation, measures are shown to be valid reflections of underlying quality and safety, are replicable and reliable
  • Transparent: methodologies are publicly available
  • Professionally Accepted: national and/or specialty leaders acknowledge that the measures are meaningful for evaluation and improvement of care
  • Benchmarked: with rare exceptions, we include only measures with comparative benchmarks

View our complete list of agencies and measures sources.

Data Validation

The measures in this Quality Rating are drawn from two principal sources. Each is validated and audited.

  1. Patient medical records, abstracted by trained professionals according to current data element definitions: Many of the quality measures in this rating are based on careful review of patient medical records to abstract specific items of clinically relevant information. The abstractors are trained, and the information can be audited both by internal hospital staff and by external auditors, such as insurance companies, Centers for Medicare and Medicaid Services, and their agents. Examples of measures which use clinical abstraction include the CMS Core Measures, Society for Thoracic Surgeons, and many more.
  2. Information on patient bills: It is a routine process for each patient’s medical record to be reviewed by trained medical records coders who assign well-defined codes to the patient’s diagnoses and surgical and other procedures. These codes appear on the patient’s bill and enable the payor to make payment determinations. There are well-established industry guidelines for coding, and there are extensive audits. Coding data are readily available and inexpensive, since every bill is already coded and no additional work is needed to gather data. However, coding is generally viewed as less reliable information because it does not provide the level of detail and specificity that clinical abstraction does (see above). Examples of measures which use billing codes include the AHRQ quality and patient safety indicators.

Other sources of data in this Quality Rating include patient surveys (HCAHPS and Press Ganey); hospital self-assessment using externally-driven criteria (some Leapfrog measures); and other information such as average length of stay derived from hospital records.

Data Display

We round numbers using standard rounding conventions.

Y axes

We display our data using a consistent approach to the y-axis. The goal is to display the data consistently and realistically. The y-axis always ranges from zero to a maximum selected according to this logic:

Rate per 1000

  • If the highest value (comparison or our data) is less than 10, use 10
  • If the highest value is less than 100, use 100
  • Otherwise use 1000


  • If the highest value (comparison or our data) is greater than or equal to 30, the maximum will be 100
  • If the highest value (comparison or our data) is less than 30, the maximum will be double the highest value, then rounded to the nearest or ten
  • If the highest value is 1 or less than 1, the maximum will be 1

For raw numbers (relatively rare on the site) we use an upper number for the range that accommodates the data.


Percentages are displayed without decimals except when the value (our data or the comparison) is a single digit. In that case, we use one decimal place. 

Exceptions are made when our data source is a public website.  In that case, we use the data as shown on the public website.

To learn more about public reporting of hospital performance measures, please see the release of "Guiding Principles for Public Reporting of Provider Performance" by the Association of American Medical Colleges. 

Northwestern Memorial is a National Leader in Quality

Northwestern Memorial Hospital and Northwestern University Feinberg School of Medicine are nationally recognized leaders in development, research and implementation of quality and patient safety processes and measures.

Awards and Recognition

Last UpdateMarch 19, 2014

Questions & Comments

If you have a question or comment about our Quality Ratings, please complete our online questions & comments form and we will respond within two business days. If your concern requires immediate attention, please call 312-926-3112 so that a Patient Representative can assist you.