Guidelines can be biased, particularly if the guideline developers stand to gain from some of the recommendations. In most cases this isn't an intentional bias, but rather implicit bias hovering beneath the clinician's consciousness. Is implicit bias influencing screening for heart disease in Down Syndrome children?
Source: Bogarapu S, Pinto NM, Etheridge SP, et al. Screening for congenital heart disease in infants with Down Syndrome: is universal echocardiography necessary? Pediatr Cardiol. 2016;37(7):1222-1227; doi:10.1007/s00246-016-1419-2. See AAP Grand Rounds commentary by Dr. David Spar (subscription required).
In 2011, the AAP Committee on Genetics provided us with guidelines on Health Supervision for Children with Down Syndrome. Of course there are many screening and health supervision issues for these children that are different from children without Down syndrome, so guidance from experts is really valuable. When I look at any guideline, one of the first things I do is look for strength of evidence ratings to help me understand whether what I'm reading is just expert consensus or a stronger recommendation supported by clinical trials or other high quality studies. For this guideline, there are no evidence ratings, and I know that at the time of publication the AAP hadn't agreed on criteria for evidence ratings, so their absence is lamentable but not surprising.
Secondly, I try to ascertain if there is any implicit bias present - whether any of the authors have a financial or professional stake in the recommendations. Well, if you want a guideline written by experts in the field, you can't help but have some degree of conflict of interest. I'd want a cardiologist to weigh in on how to screen children with Down syndrome for cardiac disease. However, it raises my antennae just a bit, analogous to articles funded and/or authored by the pharmaceutical industry. They may be perfectly honest in their writing, but it's hard to contain implicit bias since the individual isn't aware of its presence. Guess how many of the 7 Committee on Genetics members are cardiologists: exactly zero. So much for my fox/henhouse idea. But what is the best way to screen for heart disease in children with Down syndrome?
The recommendation for screening for congenital heart disease, in the section covering infants from birth to 1 month of age contains this advice:
"Heart defects (∼50% risk). Perform an echocardiogram, to be read by a pediatric cardiologist, regardless of whether a fetal echocardiogram was performed. Refer to a pediatric cardiologist for evaluation any infant whose postnatal echocardiogram results are abnormal."
That's clearly money in the cardiologist's pocket, but also it could present a major hurdle for a family that doesn't have ready access to a pediatric cardiologist. So, I was pleased to see the current study, a retrospective chart review of how 408 Down syndrome children were evaluated for heart disease, and whether screening efforts short of echocardiogram could be effective. The authors found that the combination of physical exam, electrocardiogram, and chest radiograph identified 95% of children with major congenital heart disease. They calculated that, if echocardiogram were performed only on infants who failed screening, 17% fewer echocardiograms would have been performed.
That's pretty good, but not good enough. Major congenital heart disease is of course a serious condition, and I'd want a screening test to be 100% sensitive. Raising the sensitivity bar to that level will absolutely result in many false positive results, meaning that some children would have an echocardiogram but wouldn't benefit from it, but if it still resulted in significantly less children needing an echocardiogram, it could be worth it.
Of course there are several other issues that should prevent anyone from implementing these results in clinical practice tomorrow. First, the fact that it was retrospective and based on chart review can introduce many sources of bias. For example, did the cardiologists or radiologists interpreting the electrocardiograms or radiographs have any clinical information about the children? If they were aware of clinical information suggesting a high (or low) likelihood of congenital heart disease, that might influence their interpretation of borderline findings. I wish the authors had used blinded observers to re-interpret these studies to see if the results would change.
Still, this study raises the question about whether unnecessary echocardiograms are being performed in children with Down syndrome. I hope we see an ambitious prospective study of this question in the near future. For now, stick with the 2011 guidelines; they aren't perfect, but they're the best we have at the moment.
