The release states that two “simple” new blood tests can be used to diagnose irritable bowel syndrome (IBS) by detecting antibodies that signal the presence of toxins that can cause IBS. This diagnosis, in turn, would allow patients to receive treatment more quickly. But the release has many problems that start with the headline, which claims there is now a “definitive” test for IBS. That’s an exaggeration, as the findings need further validation and they apply only to a subset of patients with diarrhea as their main symptom — something the release never explains. The release also glosses over some significant points — such as the fact that there were only 43 control patients (too small a group to draw “definitive” conclusions), and that there’s no evidence that treating patients based on these test results will actually improve their outcomes. The cost of the test and its potential harms — e.g. false-positive results that lead to unnecessary or misguided treatment — also aren’t explored in any way.
[Editor’s note: We’ve also published a review of a CBS News story about the test that shares many of the same shortcomings as this release.]
While it’s not clear how many people suffer from IBS, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD) reports that IBS affects at least 3 percent of the adult population — and probably closer to 10 or 15 percent of the adult population. The term “IBS” refers to a range of bowel symptoms including pain, constipation, and/or diarrhea. IBS is not meant to represent a single underlying cause, but in fact may represent a number of different conditions that result in functional bowel symptoms. This news release refers to an attempt to develop a test to better categorize certain patients with IBS. Though the news release implies the test is for all patients with IBS, in fact it evaluated two tests for individuals with IBS who had diarrhea as the predominant symptom. The implication that these tests may provide a diagnosis for IBS more broadly is not correct. Whether these tests hold up as being accurate when applied more broadly to patients with IBS and other related bowel conditions remains to be proven. It would also be important to see how common the test is positive in individuals without chronic bowel symptoms. Finally, even if these tests are specific for individuals with diarrhea-predominant IBS, it’s unclear if it would make any difference in their treatment or lead to a reduction in the severity of symptoms. That’s a premise that still needs to be tested.
The story does not address the cost of the IBS diagnostic tests at all. A consumer website for the tests, which are sold by Commonwealth Laboratories Inc., also did not include information about the cost of the tests.
The benefits of these tests would be a clear and early diagnosis, allowing patients to receive relevant treatment earlier. But the release’s statement that the blood tests identify these antibodies with 90% certainty is at best misleading. The story never points out that only 33% to 44% of patients with diarrhea-predominant IBS tested positive — suggesting that most people with IBS will test negative (even though they do, in fact, have IBS). Any release about a new test should explain both the sensitivity and specificity of the test.
Moreover, the release doesn’t tell readers that there is no cure for IBS. Instead, as the NIDDKD notes on its site, doctors “can manage the [IBS] symptoms with a combination of diet, medicines, probiotics, and therapies for mental health problems. You may have to try a few treatments to see what works best for you.” Or, as the Mayo Clinic summarizes, “treatment focuses on the relief of symptoms so that you can live as normally as possible.” Even without a confirmed diagnosis of IBS, patients would be able to share symptoms with their doctors. As a result, the physical health benefit here may be negligible.
No test is 100% accurate. A wrong test result may lead doctors to causes that may not actually be the problem. As such it may lead to inappropriate treatments. That’s a harm that should have been mentioned.
While the release does note the overall size (“nearly 3,000 people”) and general outlines of the study, it’s characterization of the evidence is misleading. First, this isn’t a test for IBS in general. It is a test for patients with chronic diarrhea – or IBS with diarrhea as the primary component. The release is simply wrong to use the general term “IBS” to describe this subgroup of IBS patients. Second, the release doesn’t describe that while the IBS population is large, there were only 43 control patients. It is hard to know how specific the test is without testing in more controls. In addition, the study reported (but the release didn’t mention) that the test wasn’t as good for differentiating IBS from celiac disease, and that 10-15% of inflammatory bowel disease patients (especially Crohn’s disease) also have IBS, so there’s no perfect test for these patients. Finally, such a study needs to be repeated in a new population. Tests and their thresholds are never quite as good when applied to new populations — something that wasn’t done here.
The release says IBS affects “nearly 40 million people” in the U.S., and “an estimated 10 percent of the world’s population.” But this isn’t a test for IBS — it’s a test for those with the diarrhea predominant version. It’s not clear how many people we’re talking about, but according to this study, less than half of the people with IBS meet the criteria for the diarrhea-predominant version. The release exaggerates the potential impact of the test in a way that promotes a commercial interest, so we’ll flag it for disease mongering.
We give the release credit here. It clearly notes that the lead author receives consulting fees from Commonwealth Laboratories — which is the company marketing these tests. And that Cedars-Sinai has a license agreement with the company for patent applications covering the blood tests,
The release says that IBS has been “nearly impossible to diagnose until now.” But the release also says IBS “is the most common gastroenterological disorder in the United States.” There’s a clear disconnect between these two statements. IBS may not be easy to diagnose, but it is diagnosed. Often, an IBS diagnosis is reached after other conditions have been ruled out. A diagnosis may also come after extensive additional testing. In other words, the new blood tests would be a significantly quicker and easier way to reach diagnosis. But the release should have simply said that.
The release clearly states that the tests are already on the market.
These are the first blood tests for diagnosing IBS caused by food poisoning, and the release says so.
This is a big one. The headline of the release states that “Definitive tests for irritable bowel syndrome developed…”. However, it would be far more accurate to say that “Reasonably accurate tests for diagnosing diarrhea-predominant IBS caused by food poisoning developed…”. The tests are a significant advance, but are still far from foolproof — after all, “more than 90 percent accurate” is also “almost 10 percent inaccurate.” Further, it’s not clear how many cases of IBS are caused by food poisoning, or whether identifying such patients with this test will improve their outcomes. All in all, not nearly as “simple” as the release suggests.