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In story on experimental blood test, CNN goes where few dare–the test’s sensitivity and specificity

Rating

4 Star

Categories

Blood test might make Parkinson's diagnosis easier, study says

Our Review Summary

This CNN story describes the results of a newly published study designed to see if a protein that can be measured in a blood sample accurately distinguishes between Parkinson’s Disease and a group of a rarer — but generally more rapidly disabling — disorders with similar neuromotor symptoms.

The article earns good marks for efforts to educate readers about the challenges of correctly diagnosing movement disorders and what the stakes are for patients who may get inadequate or overzealous treatment for the wrong condition. It also was detailed about the false-positive and false-negatives rates for the test–an important detail not often included in stories about screening tests.

 

Why This Matters

The advent of a simple blood test that can, with significant accuracy, help primary care physicians as well as specialists achieve a more accurate diagnosis is newsworthy. Readers of this story will be given a mostly thorough, non-hyped account of what this study found.

Criteria

Does the story adequately discuss the costs of the intervention?

Not Satisfactory

Costs are not included. Presumably a blood test would be cheaper than a test of spinal fluid, which requires a lumbar puncture.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Satisfactory

Atypical for many news stories like this, this one provided the actual specificity and sensitivity numbers for the blood test, and how that compares (in general) to the typical spinal fluid test.

That said, the story could have been a little more thorough in its discussion of what sensitivity and specificity mean. It says sensitivity is “the percentage of positives that are correctly identified, and specificity, the percentage of negatives that are correctly identified.” That’s accurate, but the story could have gone further to explain, for example, that a low specificity test means it will have a high false-positive rate (more people who don’t have the disease are erroneously told that they have it). A low-sensitivity test, by contrast, will have a high false-negative rate (more people who actually have the disease are falsely reassured by a negative test result).

Does the story adequately explain/quantify the harms of the intervention?

Not Satisfactory

Harms of the experimental test were not discussed. One important potential harm here is that there may be a much higher false-positive or false-negative rate once you use this test in the general public. For now, it’s only been tested in controlled situations where the health status of the study participant was known.

Does the story seem to grasp the quality of the evidence?

Satisfactory

The article does a good job of explaining what the study was intended to do and how it was designed. It’s especially good on explaining how blood tests like this should be validated.

Does the story commit disease-mongering?

Satisfactory

The story does not disease monger, and it did a nice job describing how common these atypical diseases are, compared to Parkinson’s disease.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

The story included two independent sources not connected with the research.

However, several of the authors in the study had connections to companies that work on this kind of test, and that wasn’t disclosed in the story.

Does the story compare the new approach with existing alternatives?

Satisfactory

The story discusses the alternative–a spinal tap test.

Does the story establish the availability of the treatment/test/product/procedure?

Satisfactory

Via the lead researcher’s discussion of what the test may do in the future, the article implies that the blood test is not yet available.

Ideally that hint should have been more explicit and perhaps accompanied by some details on what’s left before this test becomes available.

Does the story establish the true novelty of the approach?

Satisfactory

The story makes it clear that the novelty here is that this would be a blood test to distinguish among Parkinson’s disease and similar disorders, versus the more invasive spinal tap.

Does the story appear to rely solely or largely on a news release?

Satisfactory

The story does not appear to rely on a news release.

Total Score: 7 of 10 Satisfactory

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