Search results for glycoprotein (2)

Q: Did you see scientists have found a way to predict immediate death?

A: What? Lack of pulse?

Q: Very droll. No, it says interleukin-6. What is that?

A: It’s a messenger protein that some white blood cells use to stimulate other white blood cells to do stuff. If there’s a lot of it around, there’s probably inflammation, which is probably bad.

Q: And it’s new?

A: No.

Q: The story says it’s new.

A: Yes. Yes, it does.

Q: So what’s new?

A: Interleukin 6 and another marker of inflammation called C-reactive protein used to be thought of as the best things to measure if you cared about inflammation. Some researchers came up with another, called α₁-acid glycoprotein, and said it was better. This research is arguing that, no, α₁-acid glycoprotein isn’t better.

Q: Why isn’t α₁-acid glycoprotein mentioned in the story?

A: It is: the Herald’s just having font problems and calling it Î±1-acid glycoprotein.

Q: Are they right? Is interleukin 6 really better than α₁-acid glycoprotein?

A: We can’t really tell just from this one study, any more than we could really tell α₁-acid glycoprotein was better from the study that liked it.

Q: How accurate is the prediction?

A: Well, suppose you were given the name of  a 55-year old and had to guess whether they’d die in the next five years. What would you guess?

Q: Umm. No?

A: Very good. In this study, over 98% of the people didn’t die in the first five years of followup, so you’d be about 98% accurate knowing nothing.

Q: And knowing their interleukin 6 levels?

A: About 98% accurate.

Q: So it’s useless?

A: No, not at all. Comparing people at the top and bottom of the middle 50% of the distribution for interleukin-6 was like comparing smokers to non-smokers for short-term death rate. It’s just that will you/won’t you die in five years is not the right question for reasonably healthy middle-aged people.

Q: So it could be important for insurance, then?

A: In principle, if you wanted to undermine the usefulness of insurance.  It’s more useful for science — either understanding how inflammation has its effects, or trying to rule it out as an explanation of a correlation.

James Russell sent me a link to this story from a Canadian paper (originally from the Daily Telegraph).  The Herald has it too, with a very slightly less naff picture.  The research (open access) is good; the story is reasonably informative, but seriously credulous

Blood samples from over 17,000 generally healthy people were screened for 100 biomarkers, and those people monitored over five years.

In that time, 684 died from illnesses including cancer and cardiovascular disease. They all had similar levels of four biomarkers: albumin; alpha-1-acid glycoprotein; citrate, and a similar size of very-low-density lipoprotein particles.

Compare the last sentence to this graph from the research paper. The vertical axis is a combined score on the four biomarkers. The red dots are the people who died. As you can see, they didn’t all have similar values.

The research is impressive not because the prediction is very accurate, but because its less appalling inaccurate than usual.  Using standard risk factors (age, sex, cholesterol, smoking, diabetes, cancer) if you picked a random person who died and one who didn’t die from their cohort there’s an 80% chance the one with the worse risk factors was the one who died.  Adding the ‘death test’ measurements increases the probability to 83%.  Asking an experienced nurse to guess would probably be more accurate (and cheaper), but is hard to automate.

Despite the impression from the headline and lead, if you’re asked to predict whether someone will live another year, based on this sort of information, the safe bet is “yes”. Even among the 1% of people with the very worst values of the ‘death test’ biomarkers, 80% lived for more than a year and half were still alive at the end of the five year study.

Interestingly, the two republished versions lack the last paragraphs of the original Telegraph story, which talk about whether the test is useful

“If the findings are replicated then this test is surely something we will see becoming widespread,” added Prof Perola.

“But at moment there is ethical question. Would someone want to know their risk of dying if there is nothing we can do about it?”

Dr Kettunen added: “Next we aim to study whether some kind of connecting factor between these biomarkers can be identified.