How Uncertainty Overpowers Evidence in Matters of Health
Study shows that many invasive procedures are fueled by uncertainty, not facts.
Posted May 12, 2013
Dr. Sunita Sah of the Georgetown University School of Business led the study of 727 men between the ages of 40 and 75, each of whom were eligible to receive a prostate specific antigen test (PSA) -- a prostate cancer screening exam that has come under debate recently for its erratic reliability.
The question Dr. Sah's team sought to address is whether receiving inconclusive PSA test results--the equivalent of an "I don't know" response from a medical professional--would lead to what Dr. Sah calls "investigation momentum."
"The psychological dynamic of investigation momentum has two major parts," Dr. Sah explained during a phone interview. "The first is our inherent aversion to ambiguity. The second is the sense of commitment we feel once we've started an investigation and feel like we must continue."
Participants received information via email regarding prostate cancer and answered a set of questions in an attached online survey. Results were randomized into four conditions.
In the first condition, "no PSA result," participants were given information about the risks and benefits of prostate biopsies and asked whether they would have a biopsy (yes or no) and asked to rank their certainty, ranging from -100 (most certain they would not undergo a biopsy) to +100 (most certain that they would undergo a biopsy).
In the other three conditions, participants were given information about PSA tests, as well as prostate biopsies, and were then presented with a scenario asking them to imagine they'd just received their PSA test result at one of three PSA levels: normal (no cancer), elevated (cancer likely), or inconclusive. The "inconclusive" result was defined as "this result provides no information about whether or not you have cancer."
After getting the information about the PSA tests and outcomes, participants were asked to indicate (given their assigned test result) whether they would undergo a biopsy and their level of certainty in that decision.
The results confirmed Dr. Sah's hypothesis: participants who received "inconclusive" results were significantly more likely to undergo a biopsy than those who received "no PSA result." The percentages broke out to 40% vs 25% likelihood of opting for a biopsy between these groups, respectively.
Men who received an "elevated" result were also significantly more likely to opt for a biopsy versus men who received no PSA result. Interestingly, however, 38% of men who received an elevated result still opted against a biopsy, even though they had been given far firmer evidence of cancer than those in the inconclusive group.
What these results tell us is that of all the testing variables, uncertainty was the biggest catalyst moving participants toward choosing an invasive procedure. Even when they were clearly told that "inconclusive" meant that the evidence was not weighing in favor of or against a cancer diagnosis, it fueled momentum toward having a biopsy.
As Dr. Sah explains, the implications of these results do not only reflect on patients. "Physicians also want to resolve uncertainty. It is peoples' tendency toward wanting to resolve ambiguity overall--both on the parts of patients and doctors--that fuels investigation momentum."
The results throw up a red flag for all players in the medical system--patients, doctors, hospitals and insurance companies--and apply to all testing procedures in which the likelihood of an inconclusive result are high.
"Excessive medical testing is a major problem in the U.S." said Dr. Sah, "and we need to take a close look at all the variables linked to excessive testing because the ramifications are very real."