Relationship between lithotripter ownership, usage complex

Chicago-Two independent studies exploring how lithotripter ownership might affect urologists' choice of treatment for stone disease seem to provide conflicting results, although neither of the studies directly assessed individual practice patterns for lithotripter utilization.

Both studies were presented at the 2010 World Congress of Endourology and SWL in Chicago.

To explore the impact of expanded physician lithotripter ownership, urologists from the University of Michigan, Ann Arbor, took advantage of a "natural experiment" that was created in their state when two large mobile lithotripsy providers formed Michigan subsidiaries in 2005 and 2006 and offered partnership interests to practicing urologists. Over half of Michigan urologists took advantage of the opportunity, whereas previously, lithotripter ownership was low due to the state's stringent Certificate of Need requirements.

No decrease in URS procedures seen

Comparisons of patient characteristics showed that relative to patients who had URS in the post-expansion period, there were statistically significant differences in mean age, Charlson score distribution, race, and primary payer. However, the absolute magnitudes of the differences were small and not clinically significant. Rates of URS per 100,000 U.S. patients showed a slight increase in 2006 and 2007 after lithotripter ownership expansion.

"However, our study has limitations. It did not capture URS utilization in free-standing ambulatory surgery centers, although this likely does not affect the validity of our findings considering available data indicate URS is preferentially performed as hospital-based outpatient surgery. In addition, our findings are population-based, and so it is possible that individuals with lithotripter partnership shares may have decreased their use of URS," Dr. Hollingsworth said.

The rates of URS were also compared with data from Florida, a state known to have a high penetration of physician lithotripter ownership prior to 2004. These analyses showed that while the absolute rate of URS was higher in Michigan than in Florida during the study interval, the temporal trend was similar in the two states.

"Another possible concern about our study design was that the absence of any decrease in the rate of URS may not capture the whole story if in fact URS utilization was increasing at a more rapid rate elsewhere in the country," Dr. Hollingsworth explained.

In a related study, Mayo Clinic researchers sent electronic surveys to 600 urologists who were members of the American Medical Association, querying them about factors they thought were important in the treatment of stone disease, what treatment they would choose in various clinical scenarios (SWL, URS, percutaneous nephrolithotomy, or stent placement with conservative management), ownership/stock interest in a lithotripter or holmium laser, and holmium laser availability at their hospital.