defectivebrain.blogspot.com/2008/01/fake-blood-this-is-hospital-not-horror.html

I tried to be as positive as possible about it, but the quest to make fake blood is fraught with difficulty.

Real blood is cheaper, proven to work, and is commonly available.

There is of course a risk of infections etc from donated blood products but there are processes in places to ensure the risk is as low as possible.

Where the meta-analysis compares artificial vs real blood product this risk is already incorporated into the trial as the real product comes with this risk built in as it were.

I think one idea that should be used is for patients with planned surgery should make donations in advance so they get their own blood back. No risk of rejection / incompatability there but it’s not something i’ve heard being offered.

Obviously ER type trauma will not have this option which is why i’ll keep giving blood

A sidebar makes the point that the JW’s insistence on bloodless surgery has shown that many transfusions during or post surgery are avoidable. The religious can have their uses

i think what you might be missing is that the majority of patients pooled in this meta-analysis were from trials comparing artificial blood with normal transfusion blood products (6/16 RCTs but the two biggest trials by far were using blood as a control)

jama.ama-assn.org/cgi/content/full/299.19.jrv80007v1/JRV80007T2

Journal of the American Medical Association, vol 292, p1555.

Circulation, vol 116, p2544.

The New England Journal of Medicine, vol 358, p1229.

here is the blobbogram which you may not have looked at.

i think it’s really rather persuasive that there was a hint of danger in almost all the trials which only became statistically significant in a meta-analysis.

the cumulative meta-analysis moreso:

these are potentially useful products in cases where no donor blood is available, eg a battlefield, but i certainly wouldn’t choose them over donor blood for myself.

you’re welcome to, and i wish you the very best of luck!

Can’t it be said that a trial is looking for a signal, positive or negative, strong or weak – and statistical detection of the signal may come sooner or later?

Or is it that the 4 and a half month trial will for instance miss subjects who suddenly die after 5-6 months, or that changing the rules during a trial is cheating and is not statistically valid, or that one trial isn’t important enough to justify such a decision anyway, it’s the meta-analysis of different experimenters’ trials that matters?

I want to mention some other problems that I perceive: meta-analysis may be lumping together different data, as in this case where any or all artificial blood products or blood substitutes may be covered, regardless of their differences (I presume there are differences) – I suppose there is an argument for carefully designing trials to be compatible in meta-analysis; and when successive runs of the same cumulative meta-analysis are published to the general public, it may be perceived as new evidence each time, huge trials of hundreds of thousands of subjects. But meta-analysis is not new data at all, that’s the point, and this year’s cumulative meta-analysis is not itself to be added to last year’s cumulative meta-analysis, last year’s goes in the bin and is replaced by the new one. There also is a danger that either a trend will be perceived in cumulative meta-analysis, so that a future value is expected to lie beyond the range of reported meaurements – say you report 1.4, 1.5, 1.55, people expect you to keep going up to 1.7 or 1.8 but the true prediction is the latest actual value, the 1.55. Conversely, if you say that more research is needed, people may expect your finding to be confounded.

One other thing – if trials separated by long times are compared, what about variables that you haven’t accounted for? We live different lives to previous generations – passive smoking and lead in petrol have come and gone, we’re more obese, we have different vaccinations, we’re exposed to ozone and fine dust from computer printers and copiers, the planet’s magnetic field is weaker. Of course trials include a control group that is subject to all the same factors except for what the trial is for, but is that enough? Should older trials be weighted lower, treated as stale?

“Cumulative meta-analyses have saved countless lives, and they could save many more. They are clever and they are fascinating. They are the same tools you hear rubbished by big pharma, by homeopaths and by lobbyists from the $56bn food supplement industry. And you will never find them celebrated, anywhere, in popular culture.”

I assume the error concerns the first sentence, where they replaced “Ideas like cumulative meta-analysis from the world of evidence” with “Cumulative meta-analyses”.

They also replaced “But” with “And” in the final sentence. Somehow this scans better but I don’t know why.

Munin – visiting the Guardian website so you don’t have to. Oh, on you go then.
www.guardian.co.uk/science/2008/may/10/medicalresearch.health

There is enough statistical theory on sequential trials to go round: if it hasn’t been done already, someone could adapt the ideas to meta-analyses. I guess it’ll be pretty straightforward.