I have always appreciated the point Adam Jacob's tries to make but he
seems to be avoiding addressing my own - whatever the rate of unidentified
ASD/PDDs in Smeeth et al's control group (and we can debate whether it it
more or less that 1%) the very fact that
1. No-one can be certain what it is, even Adam Jacobs has failed to
prove his 1% hypothesis.
2. Smeeth et al do not appear to have sampled the control group, as
it did the case study group, and that in itself to me is questionable
practise in this case where ASD/PDD reporting, recording and diagnosing is
open to so much conjecture.
3. They have not given a total GPRD population from which case and
control groups were drawn so inferences can be made of resulting values of
ASD/PDD and non-ASD/PDD with the size of the two groups and apparent rates
of ASD/PDD identified by the raters.
In relation to 2. I note from their paper (1), describing the design
and methodolgy, they cite a number of potentially confounding issues that
could retain bias. They state that a questionnaire for all case subjects
and some controls was 'pending ethical approval'. Whether the approval was
given nor not, I assume they considered it wise to assess the validity of
whether the control group was non-ASD/PDD or not as selected from the GPRD
- unless the questionannire was used entirely for other things.
Rapid Response:
Re: Response to the two Johns
Sir
I have always appreciated the point Adam Jacob's tries to make but he
seems to be avoiding addressing my own - whatever the rate of unidentified
ASD/PDDs in Smeeth et al's control group (and we can debate whether it it
more or less that 1%) the very fact that
1. No-one can be certain what it is, even Adam Jacobs has failed to
prove his 1% hypothesis.
2. Smeeth et al do not appear to have sampled the control group, as
it did the case study group, and that in itself to me is questionable
practise in this case where ASD/PDD reporting, recording and diagnosing is
open to so much conjecture.
3. They have not given a total GPRD population from which case and
control groups were drawn so inferences can be made of resulting values of
ASD/PDD and non-ASD/PDD with the size of the two groups and apparent rates
of ASD/PDD identified by the raters.
In relation to 2. I note from their paper (1), describing the design
and methodolgy, they cite a number of potentially confounding issues that
could retain bias. They state that a questionnaire for all case subjects
and some controls was 'pending ethical approval'. Whether the approval was
given nor not, I assume they considered it wise to assess the validity of
whether the control group was non-ASD/PDD or not as selected from the GPRD
- unless the questionannire was used entirely for other things.
Regards
John H.
1. "A case control study of autism and MMR vaccination using the
GPRD: design and methodlogy", Smeeth et al, BMC Public Health 2001; 1(1):
2 and at
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=29106
Competing interests:
None declared
Competing interests: No competing interests