causality (bradford-hill criteria)

Cece · Post by **Cece** » Wed Aug 17, 2011 8:50 pm

http://en.wikipedia.org/wiki/Bradford-Hill_criteria

The Bradford Hill criteria, otherwise known as Hill's criteria for causation, are a group of minimal conditions necessary to provide adequate evidence of a causal relationship between an incidence and a consequence, established by the English epidemiologist Sir Austin Bradford Hill (1897–1991) in 1965.

The list of the criteria is as follows:[1][2]

1.Strength of association (odds ratio)
2.Consistency
3.Specificity
4.Temporal relationship (temporality) - not heuristic; factually necessary for cause to precede consequence
5.Biological gradient (dose-response relationship)
6.Plausibility (biological plausibility)
7.Coherence
8.Experiment (reversibility)
9.Analogy (consideration of alternate explanations)

How many of these do we have, between CCSVI and MS?

ikulo · Post by **ikulo** » Wed Aug 17, 2011 9:22 pm

depends who you ask

ErikaSlovakia · Post by **ErikaSlovakia** » Thu Aug 18, 2011 4:06 am

ikulo wrote:depends who you ask

Thanks - laughing is healthy

Erika

Cece · Post by **Cece** » Thu Aug 18, 2011 7:24 am

1.Strength of association (odds ratio)

This one has been debated into the ground. I tend to go with Dr. Zamboni, who found a 100% association, along with Dr. Sclafani, who has found a 99% association in clinical practice.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:30 am

2.Consistency

Not sure yet. Dr. Zamboni has found consistent findings. Again this one is debated.

3.Specificity

Specificity is coming up in some of the papers. To the best of my understanding, it's if the cause (in this example, CCSVI) is specific to the outcome (MS) or if the cause (CCSVI) can also be seen with other outcomes (no ill efects, Parkinsons, etc?).

Cece · Post by **Cece** » Thu Aug 18, 2011 7:37 am

4.Temporal relationship (temporality) - not heuristic; factually necessary for cause to precede consequence

This was the first line of attack, when we heard that MS could be causing CCSVI. Temporally, which came first? A consortium of experts in phlebology identified CCSVI as congenital malformation. It is hard to come before congenital, since that is something we are born with.

The presence of enlarged emissary veins through the canal of the skull might indicate a long-standing presence of jugular blockages, thus causing the enlargenment of those emissary veins and the skull canals, during growth during childhood, I think.

Certain types of CCSVI, such as an image we've seen of a sideways valve, are inarguably congenital. That can only happen if it was formed that way. For the valves themselves, it could be conceived that these delicate valves could be harmed in some way and react by thickening.

With this one, I'll go with the consortium of experts and agree that CCSVI is congenital. Thus temporality is achieved: CCSVI came first.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:42 am

5.Biological gradient (dose-response relationship)

The worse the CCSVI, the worse the MS?

This seems likely but I don't think it is what is being seen in practice. This is an area where more research would be useful.

I lean towards an explanation that incorporates how the immune system reacts to the brain environment set up by CCSVI. Therefore someone with terrible CCSVI but a not-overly-reactive immune system might not have as bad of MS as someone with moderate CCSVI but a highly reactive immune system.

I am going to say that the biological gradient is there between CCSVI and MS but that it is not as robust as it could be, and that the reason for the missing robustness is the multifactorialness of MS and the impact of the immune system.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:44 am

6.Plausibility (biological plausibility)

CCSVI is biologically plausible. Outflow obstructions are not healthy for any organ.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:46 am

7.Coherence

Coherence...meaning how well does the theory hold together?

I think it's the most coherent theory of MS that I've come across. Never before was there an explanation for how the events got underway, how the immune system cells got across a supposedly healthy tight blood brain barrier.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:52 am

8.Experiment (reversibility)

This is where we come in! We are the experiment. Does treating the CCSVI reverse the MS? We do talk about improvements.

We don't have an answer to this one yet. Maybe.

From the recent venoplasty/MRI research from Dr. Zamboni and Dr. Zivadinov, it suggests that getting venoplasty done greatly reduces the number of enhancing lesions showing up on MRIs. This was true in all patients except for one. So there is not universal reversibility, if we go by that research. But still pretty good.

Cece · Post by **Cece** » Thu Aug 18, 2011 7:52 am

9.Analogy (consideration of alternate explanations)

The leading alternative explanation is the autoimmune theory.