Hospital Quality Scoring and Rating Methods


Scoring Method

In order to provide a valid and reliable comparison of quality performance across providers, Quantros utilized a number of statistical methods prior to calculating percentile scores for each quality measure, quality measurement category, and clinical category. Specifically, Quantros:

  1. Removed statistical outliers at three (3) standard deviations from the mean of the log distribution of charges and length of stay within each MS-DRG terminal grouping (based on severity level, age cohort and CC cluster).
  2. Evaluated hospital performance for each quality measure within the following quality measurement categories:
    • Mortality Overall
    • Complications Overall
    • All-Site Readmissions Overall
    • Inpatient Quality
    • Patient Safety*

    *Excluded the following patient safety indicators (PSIs) from public reporting due to inconsistent coding practices among hospitals or the prevalence of false positives: complications of anesthesia (PSI 1), death in low mortality DRGs (PSI 2), abdominopelvic accidental puncture or laceration rate (PSI 15), retained surgical item or unretrieved device fragment count and transfusion reaction (PSI 16).

  3. Assigned each quality measure to one or more of the following clinical categories:
    • Overall Hospital Care
    • Overall Medical Care
    • Overall Surgical Care
    • Bariatric Surgery
    • Cancer Care
    • Cardiac Care
    • Cardiac Surgery (Major)
    • Chronic Obstructive Pulmonary Disease
    • Coronary Bypass Surgery
    • Gall Bladder Removal
    • Gastrointestinal Care
    • Gastrointestinal Hemorrhage
    • General Surgery
    • Heart Attack Treatment
    • Heart Failure Treatment
    • Hip Fracture Repair
    • Interventional Carotid Care
    • Interventional Coronary Care
    • Joint Replacement
    • Major Bowel Procedures
    • Neurological Care
    • Neurological Surgery (Major)
    • Organ Transplants
    • Orthopedic Care
    • Orthopedic Surgery (Major)
    • Pneumonia Care
    • Pulmonary Care
    • Spinal Fusion
    • Spinal Surgery
    • Stroke Care
    • Transplant of Bone Marrow
    • Transplant of Heart
    • Transplant of Kidney
    • Transplant of Liver
    • Transplant of Lung
    • Trauma Care
    • Vascular Surgery
    • Women's Health
  4. Each hospital’s performance on each measure was tested for its level of statistical significance using a z-value (based on the one-proportion z-test) which was then converted to a z-score to convert all data to a standard normal distribution (z-scores ensure an appropriate statistical distribution and equal weighting where each z-score corresponds to a point on a standard normal distribution characterized by a new mean of zero and a new standard deviation of 1; with an approximate range of -3 and +3 standard deviations).

    This statistical routine accomplishes the following:

    1. Accounts for each hospital’s standard deviation from the mean and the effect of their respective caseload volume (z-value).
    2. Prior to calculating percentile performance, the z-score converts all underlying distributions (e.g., PSI 1, PSI 2, etc.) to a standard normal distribution so that percentile performance can be accurately identified within and across quality measurement categories.

By incorporating both z-values and z-scores, this approach produces normally-distributed “statistically significant percentiles of performance” for accurately and uniformly assessing the quality of hospital care.

Eligibility Requirement for Composite Scoring and Ratings

Hospitals must receive a composite quality score ≥ 90th percentile with no lower than a "√" rating for any measurement category.

Rating Method

Using Table 1 below, each hospital’s quality rating was determined by assigning its respective percentile score to the appropriate percentile reference range and identifying the associated quality rating (√++ through √--).

Quartile Table

Distribution of Quality Ratings

The percentile reference ranges distribute hospital quality ratings as follows*:

  • 10% receive the “highest” quality rating (√++)
  • 15% receive a “high” quality rating (√+)
  • 50% receive an “average” quality rating (√)
  • 15% receive a “low” quality rating (√-)
  • 10% receive the “lowest” quality rating (√--)

*Prior to the removal of hospitals which do not meet eligibility requirements