Friday, February 21, 2014

On Autism, Environmental Toxicants, And Bias

. . . "As the authors of this review duly note but never quantify in a clear way (the reader must dig through thousands of words to pin down numbers), most of these investigations of chemical environmental factors and autism suffer limitations that include their retrospective nature, their reliance on parent memory (as opposed to data collected in real-time), and the lack of confirmation of ASD diagnoses. For example, for pesticides (which in some cases already have been banned or are being phased out; some of these studies are almost 40 years old), three prospective reports relied on parent-completed behavior checklists that aren’t autism specific. One of these studies identified a “trend” to a relationship between checklist scores and pesticide exposure, but using another developmental index, found improved scores with pesticide exposure. The air pollution findings are similarly contradictory between studies (e.g., one finds an ozone correlation; another does not; ditto for particulates smaller than 2.5 microns)." We all bring bias to what we do. Avoiding this bias in science requires vigilance. Scientists have guidelines to follow for systematic reviews that aid in that vigilance, guidelines that get a mention in the Rossignol review but largely go unused, except for inclusion of a PRISMA flowchart. There’s a reason the Institute of Medicine, in its standards for systematic reviews for therapeutic medical and surgical interventions, states that these standards for authorship on a systematic review require each team member to disclose potential COI and professional or intellectual bias; exclude individuals with a clear financial conflict; and exclude individuals whose professional or intellectual bias would diminish the credibility of the review in the eyes of the intended users. Not heeding such advice combined with an unscientific focus on a simplistic measure like “92%” does no favors for autism research. I’m sure that won’t stop the “92%” soundbite from making the rounds in certain circles and feeding the alt-med cottage industry around autism.

 Read more here.