Examination of Witness (Questions 220 - 239)
TUESDAY 19 MAY 1998
PROFESSOR H F WOODS
220. Was that recommendation from the EU, did it play no
part in your recommendation that was announced?
(Professor Woods) No part whatsoever. It is the case,
and you raise a very interesting point, that from time to time
matters, questions, chemicals that the Committee on Toxicology
is considering either are being considered by committees in other
countries or have been. We are not influenced, we come to our
own conclusions. We do not come to conclusions in order to match
or agree with the opinions expressed by other expert committees.
It is almost obvious that some of the data bases that expert committees
use, whether it be in this country or in the United States or
Europe, will be the same.
221. So this recommendation from the EU had no influence
on your decision at all?
(Professor Woods) No. What interested us, however,
is that there are other committees, for example the Committee
on the Safety of Medicines in this country, the Swedish authority
responsible for comparable decisions and also the French authority
which is responsible for comparable decisions, which have also,
we now know, reached the same conclusion as ourselves. I cannot
give you the data bases upon which they reached those conclusions.
222. But without that you still unanimously agreed with them,
you say so in your memorandum.
(Professor Woods) We agreed with them, yes, but that
is in retrospect.
223. But you did not know what the scientific base of their
recommendation came from?
(Professor Woods) We can speculate with a reasonable
degree of certainty that the data bases that those authorities
and committees used were identical to or almost identical to our
own data base.
224. So they may have used Dalton and Dalton as well?
(Professor Woods) As is exemplified by the NAS report,
yes, I presume so.
Mrs Organ: In other words everybody is using the same discredited
report.
Chairman: As it seems everybody is using Dalton and Dalton
we shall ask you some questions about Dalton and Dalton. Mr Hurst.
Mr Hurst
225. I think Dalton and Dalton are obviously the two names
to conjure with here today. Professor, if I can ask you this because
I have got to get it clear in my mind. Your committee says the
only human evidence that was relied upon was that contained in
the Dalton and Dalton study?
(Professor Woods) Yes.
226. In your memorandum to the Committee it says: "The
Committee recognises the deficiencies in the Dalton and Dalton
study in its statement" and it ". . . would not have
been used by itself to derive a numerical recommended intake .
. . The dataof the Dalton and Dalton study are weak butconsistent
. . ." What concerns me a little is at the end it says "given
the other data on dose, duration and time to adverse effects in
both animals (dogs and rats) and humans." and that final
sentence implies that in fact there is other evidence concerning
the human condition which was studied in Dalton and Dalton.
(Professor Woods) There are undoubtedly other papers
that we referred to. I see what you mean now. We are certainly
correct in saying the sense we meant to put over in that memorandum
was that Dalton and Dalton was a major factor or a major paper
upon which we based our conclusions but we did look at other human
data, some of which certainly is referred to, for example, in
the NAS report.
Mr Mitchell
227. On toxicity over a certain level?
(Professor Woods) Yes.
Mr Hurst
228. With regard to the other human data, and it is not for
me to speculate, if you were preparing a strong adversarial case,
if in fact you were Mr Mitchell in a court room, I would have
thought you might go for stronger evidence than Dalton and Dalton
which on your own admission is not the strongest of evidence to
put before the committee.
(Professor Woods) No, but there are two particular
aspects of Dalton and Dalton which were essential for and very
important to our deliberations. That was the evidence in relation
to the fact that duration of dosage, in other words time during
which vitamin B6 was taken, was important, and also another important
matter was the description by Dalton and Dalton of the recurrence
of symptoms in their subjects when vitamin B6 intake was restored.
These are rather important considerations.
229. I think you will appreciate, Professor Woods—I
speak for myself and most people on this Committee who are lay
people who do not have a main scientific background—it certainly
has been put to us that there are very substantial criticisms
of the Dalton and Dalton study to such an extent that it should
not be validly relied upon. I wonder if it would be helpful if
I can put to you some of those criticisms to see your response.
(Professor Woods) Yes, of course.
230. The first point that has been put is that there was
no untreated control group.
(Professor Woods) The Dalton and Dalton study compared
two groups on vitamin B6. It is a fact that there was no untreated
group, yes. Certainly I accept that as one way of looking at the
study but I do not think that it negates the study.
231. Would it be so that in most reliable scientific studies
that in fact there would be very tightly controlled groups which
are surveyed?
(Professor Woods) In what way would the control group
be designed in this case if you wanted to revise Dalton and Dalton
again?
232. I do not think it would be for me to suggest the exact
terms. I would have thought it is relatively in the public domain
if you are making comparisons between two groups that they should
be fairly tightly controlled and indeed contemporaneous?
(Professor Woods) Do you mean that there should be
a separate control group or do you mean that the control of entry
into the two groups studied should be tightly controlled?
233. It probably should be both actually. I wonder if I can
move on to the retrospective nature of the study. What would you
say to that?
(Professor Woods) It is a common finding that studies
on toxicology in man are retrospective, that is the nature of
those studies. I accept that and the committee accepts that. There
has been no long-term safety study of vitamin B6 in man.
234. I think it is notorious even in the world in which Members
of this Committee operate that those who seek to recall how they
voted in the last election normally recall that they voted for
the winner and therefore there is a certain inaccuracy of recall.
Is that the fact in medicine?
(Professor Woods) It is, I assure you, the fact in
medicine, yes. All individuals, including doctors, have difficulty
in recall.
235. Would it be right that leading questions would be used
as part of the methodology?
(Professor Woods) No, it is not right that leading
questions would be used but where are the leading questions?
236. Would your judgment be that they were using leading
questions in the study by Dalton and Dalton?
(Professor Woods) I am not a lawyer and, therefore,
I cannot define what a leading question is but if you mean by
that that the questioner by the very nature of the question suggests
to the subject being questioned the answer, the answer is of course
not.
237. Yes, but there are degrees of suggestibility, are there
not, in these things? It may be the implication of an answer or
the narrowing of choices to answer. Would your observation of
the study be that any of those faults could be found?
(Professor Woods) I think it is essential that in
the perfect study, particularly one in which patients or subjects
are questioned, the questions must be designed in such a way as
to avoid those pitfalls.
238. Since the publication of your report, in fact, and it
has already been touched upon, the American Academy of Sciences'
report has drawn conclusions and they presumably would have looked
back at a wide range of literature and indeed there seem to have
been quite a number of American studies they would have had access
to.
(Professor Woods) Yes.
239. Their conclusion is, I think, ten-fold your recommended
dosage.
(Professor Woods) Yes.
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