Analysis bolsters expulsive therapy's cost-effectiveness

January 15, 2013

Patients who receive medical expulsive therapy as initial management for renal colic incur significantly lower episode-related expenditures than those undergoing early endoscopic stone removal, but are significantly more likely to have return visits to the emergency department, report researchers from the University of Michigan, Ann Arbor.

Editor’s note: The research discussed in this article is a separate, updated analysis of data reported in the Urology Times article, "Expulsive therapy less costly than surgery for renal colic" (January 2013, page 1).

Ann Arbor, MI-Patients who receive medical expulsive therapy as initial management for renal colic incur significantly lower episode-related expenditures than those undergoing early endoscopic stone removal, but are significantly more likely to have return visits to the emergency department, report researchers from the University of Michigan, Ann Arbor.

In order to understand the effect of medical expulsive therapy (MET) on health spending and resource use among patients with renal colic, the authors conducted an instrumental variable analysis exploiting variation in recommended therapy by day of the week of the patient’s first visit to the emergency department (ED). Data were derived from the MarketScan Commercial Claims and Encounters database, which was searched to identify adult men who presented with an incident ED visit for stone disease between 2002 and 2006. The study included 1,835 men who received MET (alpha-blocker or calcium channel blocker) and 4,397 men who underwent early stone surgery.

Total episode payments were more than $10,000 less for patients who received MET than for those who underwent early stone surgery. There was no significant difference between the two treatment groups in the proportion of patients with a hospitalization. However, a significantly higher proportion of MET patients revisited the ED compared with the early stone surgery group (69% vs. 40%), reported first author John M. Hollingsworth, MD, MS, assistant professor of urology at the University of Michigan.

ED visits may mitigate cost efficiency

"According to the most recent guidelines from the AUA and European Association of Urology on ureteral calculi management, MET may be prescribed for patients amenable to conservative measures. Insofar as MET reduces the need for surgical stone removal, it may lower expenditures over the stone episode. However, this gain in cost efficiency may be mitigated if patients have more health encounters while waiting for stone passage," said Dr. Hollingsworth, who presented the study results at the 2012 American College of Surgeons Clinical Congress in Chicago.

"The findings from our study address a gap in information on health spending and resource use in patients who present to the ED with an index case of renal colic and should be useful to clinicians in informing patients about their alternatives. Knowing that in choosing MET to avoid surgery and its attendant risks there comes a tradeoff of an increased likelihood of ED revisits might lead some patients to opt for early endoscopic stone removal instead."

Dr. Hollingsworth explained that the instrumental variable analysis method, which can control for unmeasured differences between groups, was used in the study because the MarketScan database does not capture information on stone characteristics that can affect treatment selection.

"The instrumental variable analysis identifies a variable that is highly associated to the type of treatment received but that is unrelated to the outcomes of interest except through its effect on treatment received. Therefore, it is a way to ‘pseudo-randomize’ patients to create groups that are more balanced with respect to measured and unmeasured confounders," he said.

Findings from various data analyses supported the validity of day of the week of presentation to the ED as the instrument, including that patients who presented on the early weekend (Wednesday through Sunday) had an 8% greater likelihood of receiving MET than those whose ED visit was on a weekday (Monday through Wednesday).

The study was partially funded by the PhRMA Foundation.