Two medical studies show that when it comes to medical behavior, money—while it can be a motivating factor—is not a reliable lever for shaping patient or professional behavior.

For example, while a recent study showed that drug prices can come between patients and medication adherence, a March editorial in the American Journal of Managed Care by researchers associated with the University of North Carolina at Chapel Hill and Yale University indicates that higher patient adherence and lower cost do not necessarily go hand in hand. In the study, the doctors found that the typical value-based insurance design that provides “an absolute price reduction may have a marginal effect on overall adherence due to non-economic factors.” Researchers began with patients who were switched from a plan with a fixed medication co-pay to a plan with a co-insurance policy, meaning instead of a flat rate for generics vs. brands, patients worked within co-insurance gradients. That is, they could pay 5-10% for the price of a generic, 20% for medications for which generics didn’t exist, and 50% for what were considered choice brands.

The plan changeover occurred in 2004 and surveyed members’ use of blood-pressure medications, beta-blockers, statins and asthma controllers. The result: “a disproportional decline in adherence in all four drug classes, including the two where out-of-pocket-costs actually declined because of co-insurance.” The researchers suspect that adherence may have dropped because this same co-insurance policy probably increased the cost of office visits, essentially diluting the impact of the medication-pricing plan.

But the diluted effect of savings is not enough to completely dismiss the impact drug prices can have on use. A 2009 study, also published by AJMC, found that a free generics program combined with higher co-pays for branded drugs did not result in a mass migration to no-cost medications. In this instance, researchers looked at statin users and diabetics and found that statin users were more inclined to pick up free prescriptions than diabetics, whose generic use tended to be among metformin users. The 2009 conclusion, like that among the more recent research, was that altering co-pays “is unlikely in and of itself to result in a complete conversion” to generics.

But another study, appearing in JAMA Internal Medicine, showed cost did drive medical behavior. When doctors saw what lab tests cost before they ordered them, they became stingier as regards ordering tests that could result in high patient medical bills. The need for diagnostics is a regular discussion topic, with recommendations for screenings such as mammograms being part of a regular back-and-forth regarding necessity and effectiveness, as well as being deployed as a measure of physician vigilance and leaving nothing to chance (or possible liability).

These researchers also wrote that “most physicians do not know how much tests cost.” These factors aside, they homed in on their hospital’s 35 most-frequently ordered lab tests and the 35 most expensive ones and monitored physician behavior in two ways: first, there was a six-month period in 2008-2009 in which no fees were displayed and usage tracked. This was followed by a six-month period spanning 2009-2010 in which these same tests were monitored, but doctors had a preview of the Medicare-allowable charge on some of them. The result: a 9.1% drop in test use among those with prices attached, with a “marked decrease in the ordering frequency of comprehensive metabolic panels…and an increase in ordering frequency for basic metabolic panels.”

Of perhaps more interest is just how small an incentive doctors received beyond price information: nothing. There was no educational ramp-up or request that docs keep costs down. Researchers acknowledge that the test period was a short one, and the $400,000 saved in tests is small, but note that if such practices were rolled out on a larger scale, there could be a substantive impact.