“Blood test detects 50 types of cancer” – we have already followed this path |


Poor, incomplete and servile news coverage of screening tests is one of the most clearly established problems in health news coverage – something HealthNewsReview.org has revealed countless times over the past 15 years.

A public relations press release 22 days ago – from “a health company whose mission is to detect cancer early” – touted the results of a study that the company said showed a test. “the ability to detect more than 50 cancers with a single blood draw could transform early cancer detection as a complement to existing screenings. ”

There’s a lot to undo from that kind of claim, and I haven’t seen any news coverage that does. There may be some that I haven’t seen.

This week, The Guardian has drawn the ire of many observers on social media and the email lists I follow.

The Guardian reported: “It correctly identified when cancer was present in 51.5% of cases, at all stages of the disease, and misdetected cancer in only 0.5% of cases.” But there was no analysis of what those numbers meant to patients. The test’s 51.5% sensitivity – its ability to find cancer when cancer was present – means that nearly half of the cancer patients who would get the test would not have detected cancer this way. For patients with early cancers – the kind you hope to catch with an effective screening test – the sensitivity was much lower. The test had a sensitivity rate of less than 17% for stage 1 cancers and a sensitivity rate of 40% for stage 2 cancers. in the newspaper article where the study results were published, sought to minimize the relevance of the sensitivity statistics. But the news coverage I saw bypassed the whole issue of sensitivity.

There was not even a truly independent perspective presented in the story. It sounded like a public relations message. It wasn’t hard to find healthy skeptics on social media too.

Dr. Susan Bewley criticized The Guardian on Twitter:

Another British doctor needed only one word to react to the news:

In the United States, cancer specialist Dr. Kevin Knopf tweeted:

The Guardian was not alone; you can find dozens of undisputed stories online.

Let me be clear on this: like Dr. Bewley suggests that there are possible benefits but inevitable harms whenever mass screening is done. Any reporter or news organization writing about screening tests must discuss these trade-offs.

Because we have written so much about this issue, we have a primer that journalists and the general public should know about …

Understanding of medical tests: sensitivity, specificity and positive predictive value

Alone Check out our archives of shoddy media messages on cancer blood tests… Universal blood tests … “simple” blood tests for cancer. You will see the damage that is done in case of bad communication to the public.

While I was looking for The Guardian story, I saw that they also released this story this week:

The Guardian allowed one author of the study to state that this “confirms … coffee consumption is protective against severe liver disease.”

Later, the story turned upside down. It took 11 paragraphs of the Guardian – or 365 words – to reveal:

However, the study has limitations, including the fact that it cannot prove that coffee itself reduces the risk of chronic liver disease, while participants were only questioned about their coffee drinking habits at one point in time.

Confirm that the coffee is protective? Or can’t it prove that coffee reduces risk? You can’t have it both ways.


Please enter your comment!
Please enter your name here