CMS does not adequately assess the effect of surgery volume when calculating its Overall Hospital Quality Star Ratings, according to a study published in JBJS Open Access.
CMS excludes some quality measures for hospitals that perform fewer than 25 surgical procedures over a three-year period. Researchers from the Hospital for Special Surgery in New York City hypothesized that exclusion could alter hospitals' ratings, since they're graded relative to one another.
For the study, researchers assessed four measures CMS excludes from star ratings calculations for low-volume hospitals:
- Complication rate for coronary artery bypass grafting
- Readmission rate for coronary artery bypass grafting
- Mortality rate for total joint arthroplasty
- Readmission rate for total joint arthroplasty
Researchers calculated estimated values for the above measures for low-volume hospitals. They then repeated CMS' star ratings calculations using these estimated measures to identify which hospitals had the same, better or worse ratings.
When researchers inputted estimated measures for total joint arthroplasty complications, more than one-third of hospitals had a different — and often lower — rating. Ratings were unchanged when incorporating the other three measures into calculations.
"The CMS star ratings do not fully represent the risks of undergoing procedures at low-volume hospitals, potentially misrepresent quality across facilities, and hence are of uncertain utility to consumers," the researchers concluded.