This story about a Parkinson’s disease test that was recently approved for use in the U.S. displays a fundamental misunderstanding of the purpose of the new test.
The DaTscan is intended to help doctors rule out Parkinson’s disease when the underlying cause of their symptoms is difficult to determine, but the patient example and overall tone of the story convey that the test is meant to uncover Parkinson’s cases that other tests and exams have missed. The story does not address the lack of evidence about whether this test can improve patient outcomes. The story fails to offer readers any independent voices, relying only on doctors at institutions that are actively marketing their ability to offer a test that not all of their competitors have. The story also fails to address the potential harms of this test, including a risk of thyroid cancer if uptake of radioactive iodine in the test solution is not properly blocked.
Parkinson’s is a common neurological condition that causes tremor and difficulty with moving. It generally starts in people later in life and can lead to major functional impairment. The diagnosis is a clinical one – meaning that the patient describes symptoms and the physician performs an exam that is consistent with Parkinson’s disease. For many individuals, this diagnosis is straightforward and tests such as the one described here would be unnecessary. For some patients with early, mild symptoms, the diagnosis can sometimes be more difficult to make with certainty. However, for these individuals, many physicians would not want to start treatment because of the problem with medicines leading to tolerance with time that limits their long-term effectiveness. So the role for this test, probably is for the minority of patients with functionally impairing symptoms in whom the diagnosis isn’t clear when being evaluated by a specialist. The problem with tests such as this is that it is hard to limit use to the minority in whom it can help. Rather they are promoted and end up being overused in the routine patient in whom the test really isn’t needed to make the diagnosis. This is how technology adds to the cost of health care without improving outcomes.
Yes, the story reports that a DaTscan costs about $1500. Oddly, instead of reporting what the hospitals featured in the story charge for a scan, the story attributes the price estimate to a quote taken from an article by Medscape Medical News. But there is a much higher price listed on the web site of the Michael J. Fox Foundation for Parkinson’s Research, which estimates a DaTscan costs almost $3000. Still, because the story does address cost we will give it credit on this criterion.
Michael J. Fox Foundation for Parkinson’s Research page on DaTscan:
The unsatisfactory rating on this criterion also is related to the fundamental misrepresentation of the purpose of the DaTscan. The story repeatedly refers to getting patients on drug treatment for Parkinson’s earlier. The only patient example presented to readers is of a man who says the test was the key piece of evidence that finally revealed he has Parkinson’s after he was repeatedly told by other doctors that he had some other condition. In fact, conventional examinations are more likely to lead to a Parkinson’s diagnosis than is a DaTscan test. The intended use of the test is to identify people who have been misdiagnosed as having Parkinson’s when actually their symptoms are caused by some other condition. Also, while the story refers to clinical studies, it doesn’t give readers any specifics about the results of those trials.
The story does not mention potential harms, including the potential cancer risk from radioactive iodine that is injected into patients as part of the DaTscan. The drug label warns that clinicians must use a blocking agent to prevent the patient’s thyroid from taking up the radioactive iodine.
The story should have also reported that although adverse reactions were uncommon in clinical studies, some people did have hypersensitivity reactions such as rash and itching, and that less than 1 percent of patients reported mild to moderate headache, nausea, vertigo, dry mouth or dizziness. The story would have been better if it also noted that since the studies included fewer than 300 patients, side effects that occur only rarely might not have shown up.
FDA-approved label for DaTscan:
As noted above, the story creates an impression that the DaTscan is used to find cases of Parkinson’s, when actually the opposite is true: the test helps rule out Parkinson’s in patients who actually have Essential Tremor or other conditions. The story not only fails to accurately describe the evidence, it gets it entirely backwards.
The article does a poor job describing who this should be used for. Parkinson’s is a clinical diagnosis that is readily made by physicians without the need for such a test. Although the story does report prominently that the DaTscan test is intended for use in “difficult-to-diagnose cases of Parkinson’s disease or other parkinsonian syndromes,” it should have noted that these groups represent only about 5 percent of patients. What’s more, the patient example and other sections of the story would likely lead readers to believe that the test is useful in many patients who do not fit the population for which the test was approved. Indeed, the story generally flips the intended use upside down, creating an impression that the DaTscan detects cases of Parkinson’s disease that other tests and exams may miss, when actually the test is intended to help doctors rule out Parkinson’s in patients who actually have some other condition. A news release from GE Healthcare says the test may help reduce the cost of care by “preventing patients from receiving misdiagnoses or inappropriate treatment.”
GE Healthcare news release:
All of the experts quoted in the story appear to work at institutions that are promoting their ability to offer the DaTscan test. A truly independent expert source might have raised some of the important issues discussed in our review.
In the overwhelming majority of cases, a diagnosis of Parkinson’s disease is made through clinical examination of the patient, including the specific pattern of tremors and other movement difficulties, followed by a test of drugs to see if they help ease the symptoms. The story not only fails to accurately describe conventional clinical tests and examinations used to establish a Parkinson’s disease diagnosis, it misreports the primary purpose of the DaTscan test.
The availability of the DaTscan test is the main point of the story. It reports the test was approved by the FDA in January 2011 and is now available at more than 80 hospitals in the United States. It also reports that the test was approved for use in Europe a decade ago.
The story does note that the DaTscan test became available in the United States only this year. However, as noted above, the misrepresentation of the purpose of the test will likely mislead most readers about what is actually new about this test.
The story does not appear to rely on a news release. However, it does not tell readers much information beyond what they would get from reading just the hospital news releases touting this test.