COVID, Colonoscopies, and Certainty
OK, just “follow the science.” What the hell does that mean? Philosophers of science know that scientific knowledge is value-laden. We decide what to study, how to study it, and then how to analyze results and draw inferences based on our prior beliefs that something is worth studying and that certain study designs are preferable to others. These judgments are never purely methodological. Furthermore, science, by its very nature, is constantly changing, both in its methods and in the results generated by those methods. The essence of science is to question received wisdom, to attack dogma, to churn.
Through the pandemic, there have been debates about the science behind immunizations, masking, quarantine, and treatment. Such debates focus on COVID but they are not unique to COVID. They are the essence of any situation in which strong scientific research is trying to find valid answers to tough questions. Good new studies ought to lead to questions what we once thought we knew. Policy makers inevitably claim to be more certain than the science allows.
To put the COVID debates in perspective, we could look at debates about cancer screening. There we find constantly changing recommendations about PSA for prostate cancer, mammography for breast cancer, and now, about screening colonoscopies for colorectal cancer.
A recent study evaluated the efficacy of such colonoscopies. Researchers enrolled nearly 100,000 patients. Some were offered colonoscopy screening. Others weren’t. Of those we were offered it, fewer than half accepted the offer and got a colonoscopy. The analysis looked at whether more cancers were found and more lives saved in the group that was offered colonoscopy.
As with COVID studies, the results can be sliced and diced. Fewer people in the group that was offered screening were ultimately diagnosed with colorectal cancer than in the other group. This primary finding was touted in the published paper. The authors concluded that being offered just one colonoscopy screening led to an 18% reduction in the risk of getting colorectal cancer over the next ten years. But that isn’t the end of the story. In addition to looking at cancer diagnoses, they looked at survival. Neither all-cause mortality nor mortality from colorectal cancer differed between the two groups was not significantly different. Screening did not save lives.
Experts were surprised and disappointed. Some continue to believe that the test is useful. Adam Cifu, a practicing internist, commented, “Am I going to stop recommending this? No way. I’ve had patients die of colon cancer.” Old beliefs die hard. Vinay Prasad, on the other hand, suggested that we should stop using this test and, instead, use other screening tests for colon cancer. You can watch a fascinating debate about the topic here. So should we stop doing routine colonoscopies. Instead of following the science, perhaps we should follow the money.
What does it have to do with COVID? There, too, experts and others disagree about the best approach to both prevention and treatment. There, too, there is debate about which endpoints are most important. With COVID, the results are almost the opposite of those found in colon cancer. Immunization may not decrease the number of people who get infected but it does decrease the percentage of infected people who are hospitalized and who die. But the choice of endpoints is not, in itself, scientific. All are valuable. Following the science gives us data. It doesn’t tell us how to interpret that data.