For messy preliminary data a systematic review is perhaps better than meta-analysis to get an idea about what the state of the research is. In this case, we have one researcher, Zamboni, who has generated the initial positive results. Most of the attempts at replicating this research have either had mixed or negative results. There is little consistency among the various studies.
There also appears to be a correlation between lack of blinding and positive outcomes. Zamboni’s original data was unblinded, and dramatically positive. In a follow up study he claims to have addressed the concerns, but critics point out that he gives no indication of how assessments were blinded and how successful the blinding was. Attempts to replicate the data with well-blinded protocols have tended to be negative.
It is a good rule of thumb that when a phenomenon tends to disappear when proper blinding protocols are put into place, then the phenomenon is likely not real.
The current meta-analysis can really only reach one conclusion – that the data is preliminary and mixed, with various degrees of blinding and overall quality, and therefore a meta-analysis cannot reach any conclusion as to the data. The researchers really could have stopped there. Actually doing the meta-analysis was pointless, and generated what the authors acknowledge is likely a spurious outcome. This outcome, however, is likely to add confusion to the reporting of the data.
A better approach to this set of studies is a science-based systematic review, taking into consideration the relationship between the quality of each study (especially the quality of the blinding) and the magnitude of the correlation between CCSVI and multiple sclerosis. The emerging consensus as more studies are being done is that there is no correlation.
Comment by JurijD
The exact same thing is happening here in Slovenia, where Zamboni has successfully found allies in certain private clinics near the border between Italy and Slovenia that have begun a systematic campaign propaganda aimed at the public and legislators to have balloon angioplasties to “relieve” the supposed CCSVI in MS paid for by the regular government health insurance.
So far they have not succeeded but public pressure is mounting and the doctors who are pushing Zamboni’s agenda have often publicly said they are conducting a clinical study to measure the effectiveness of balloon angioplasty to relieve the symptoms of MS.
When asked how the study is being conducted they specifically started to make up reasons why BLINDING is not at all necessary in their study.
I can see them coming out with a bogus blinded, poorly executed study in a year or so that they will proceed to use as a shield against all criticism.
If this indeed transpires, I don’t think the general public will be swayed by “academic” contra-arguments about the finer points of clinical study design and blinding and these guys will get exactly what they want. – MONEY