A Review of “Early Downward Trends in Neurodevelopmental Disorders Following Removal of Thimerosal-Containing Vaccines”
Anecdotally, Geier & Geier (2006) has sparked sharp discussion in the online autism world. The critiques of that article cover a broad range of problems. These range from concerns with the scientific objectivity of the journal, to problems with the VAERS database. At the same time, Geier & Geier (2006) has been informally heralded by those who wish to advocate the thimerosal etiology theory of autism, as a strong proof.
There are three primary reasons Geier & Geier (2006) is invalid in terms of the CDDS data. I will present these and argue that such threats negate the value of this study.
Misuse of Data
The data in this study are supplied by the CDDS. This relies on the change between quarterly reports to calculate new cases. Unfortunately the CDDS has a document that states the changes between quarters can not be counted as new cases (DDS, 2005). The persons may have already been in the CDDS and receiving services under a different category or their paper work may have taken a while to collect and process, even though they were already receiving services. When such uncontrolled data are employed they contain errors of random and systematic error (Friis & Sellers, 2004).
Arbitrary Assignment of Point of Change
One is not permitted to simply look at a graph and pick the point of change as occurred in Geier & Geier (2006). This a very fundamental error. Instead the authors should have identified a point when the thimerosal had been removed to test this hypothesis.
Application of More Restrictive Criteria
In July 2003 the CDDS applied a more restrictive criteria to the eligibility requirement for their autism services (Rollens, 2004). This severely confounds the decrease that is noted in this period, as it makes it almost certain that there would be a drop. Furthermore, a review of Figure 4. shows that the decrease does not occur until after July 2003, and the implementation of the more restrictive criteria. This is not clear in the correlational graph in Geier & Geier (2005).
I conclude that Geier & Geier (2006) does not necessarily show what it claims to. I strongly second the position that Joseph at the "Autism - Natural Variation" blog, put forth, namely that the Journal of American Physicians and Surgeons peer reviewers re-examine this study and consider retraction.
Notes: A letter to the editor outlining these points will be submitted for publication in the Journal of American Physicians and Surgeons.
The following links are to blogs which discuss this issue and which serve as references to this post.
Department of Developmental Services (2005). Data Interpretation Considerations and Limitations.http://www.dds.ca.gov/FactsStats/pdf/CDER_QtrlyReport_ Consideration_ imtations.pdf. Accessed Friday January 13, 2005.
Department of Developmental Services (2006). Quarterly Client Characteristics Reports.http://www.dds.ca.gov/FactsStats/quarterly.cfmAccessed Friday January 13, 2005.
Friis, R. H., Sellers, T. A. (2004). Epidemiology for public health practice, 3rd ed. Sundbury, MA: Jones and Bartlett Publishers.
Geier, D. A., & Geier, M. R. (2006). Early Downward Trends in Neurodevelopmental Disorders Following Removal of Thimerosal-Containing Vaccines. Journal of American Physicians and Surgeons. 11(1), 8-13.