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Volume of Service and Quality

By April 8, 2019Commentary

I have been storing up some more esoteric, scholarly studies and this week I am going to try to summarize a number of them.  The first is one on the relationship between volume and quality for more complex therapies, carried by the Journal of Health Economics.   (JHE Article)   The authors used a natural experiment in Sweden created by the opening and closing of cancer clinics.  Data from 1998 to 2007 was used.  Breast, prostate and colon cancer surgery were the treatments used, over 100,000 episodes in the relevant period.  In Sweden, patients are assigned to a clinic based on geographic location (how would you like to have that restriction on your choice of provider, but don’t worry they are all equally good!), so when one closed the patients just were shifted to another one.  In this way outcomes for patients could be followed by clinic without too much concern for patient mix issues.  Although volumes at remaining clinics increased when one closed, by looking only at patients in the catchment area before the closure, you could see the effect of greater volume on their outcomes.  Four-year post surgery mortality was used as a primary outcome.  They also looked at complications, readmissions, subsequent cancer surgery rates and length of stay.

Five net closures occurred during the study period, resulting in the average number of patients treated per clinic going from 151 to 195.  Comparing regions with clinic closures with those with no closures, trends in survival were similar prior to the closures.  After the closure, those clinics affected by picking up increased patient volume showed a clear comparative mortality improvement.  If the number of procedures went from 70 to 130 per year, mortality declined by 2.7 percentage points or 11%.  There also seems to be a point at which there are diminished returns for increased volume.    Complications and additional surgeries were also reduced.  Testing for possible explanations of the volume effect, the researchers conclude that learning by doing, for the individual surgeon, not for the clinic as a whole, is the most likely one, which seems quite logical.  (I know the more posts I write, the better they get.  Or maybe not!!)  The authors suggest that a further concentration of volume, by insisting on a 160 case per year minimum would lead to closure of 50% of clinics, and decrease four-year mortality by 2%.  Might reduce spending as well.

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