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House CallApril/May 2010 Issue

Research Roundup: Germs, Autism, Celiac Screening and More!

The latest medical news for people with allergies and food sensitivities

More Germs, Fewer Allergies?

Inflammation is a key part of our immune system’s defense network, but how inflammatory processes develop and are regulated is not well understood. A study, led by a researcher at Northwestern University, found that wider exposure to infectious microbes in early childhood predict lower levels of a telling marker of inflammation, C-reactive protein (CRP), in adulthood. Lower CRP means lower inflammation levels; inflammation plays a key role in the development of allergies and other medical conditions. Much of the research to date on C-reactive protein has focused on its role in predicting heart disease, and most of the research has been done in developed countries, which have relatively low incident levels of infectious disease.

The research group used data from a study in the Philippines, which has a higher rate of infectious diseases. Participants included women and their children, who had been followed since 1983. The team looked at data from over 1,400 of the children, now in their 20s (some were in utero when the study began) and found that CRP was five to seven times lower for subjects in their 20s in the Philippines than for Americans of similar ages.

Filipino infants and toddlers experience many more infectious diseases than American youngsters. The research suggests that germaphobes may actually be doing a disservice to their babies. By trying to protect kids from microbes, “We may be depriving developing immune networks of important environmental input needed to guide their function throughout childhood and into adulthood,” says lead author Thomas McDade, associate professor of anthropology. “Without this input, our research suggests that inflammation may be more likely to be poorly regulated and result in inflammatory responses that are overblown or more difficult to turn off once things get started.”

The work was published in December 2009 in Proceedings of the Royal Society B: Biological Sciences.

Autism Clusters in California

In a study designed as a step toward uncovering possible geographic risk factors for autism in California, researchers at the University of California, Davis, have found ten clusters where incidence of autism is significantly higher than surrounding areas. The investigators looked at some 2.5 million births in the state between 1996 and 2000 and mapped the birth locations of the children later diagnosed with autism, about 10,000 of them.

“What we found with these clusters was that they correlated with neighborhoods of high education or neighborhoods that were near a major treatment center for autism,” said Irva Hertz-Picciotto, a researcher with the University's MIND Institute and senior author of the paper, in a press release. Because children born to more highly educated parents are more likely to receive a diagnosis, and because demographic differences—particularly in parental education—within and outside the clusters were so striking, researchers believe they are not the result of an environmental exposure, such as pollution.

This study comes on the heels of two new estimates of autism prevalence, one that found an incident rate of 0.9 percent among 8-year-olds and one that revealed a rate of 1.1 percent in children aged 3 to 17. Both underscore the fact that autism is an important public health concern and the need to further research risk factors and provide support services for those with ASDs and their families.

Celiac Screening

Blood testing for antibodies, particularly tissue transglutaminase (tTG), is usually the first step toward a diagnosis of celiac disease. When tests come back positive, doctors typically recommend a biopsy of the small intestine to confirm diagnosis.

Researchers in Léon, Spain, set out to evaluate the predictive value of tTG antibodies in both adults and children to determine whether intestinal biopsies could be avoided. The study included 324 patients with celiac disease. Based on the analysis, up to 95 percent of children and 53 percent of adults would be correctly diagnosed without biopsy. The authors concluded that high levels of tTG antibodies in the blood might be sufficient to diagnose celiac in kids but that biopsy shouldn't be avoided in adults.

Could study results point to possible changes in the way children are screened for celiac disease in the United States? Not likely, says Stefano Guandalini, MD, medical director of the University of Chicago Celiac Disease Center.

“By not biopsying children who have very elevated tTG, there’s always the risk of misdiagnosing celiac disease in children who had a false-positive test, something that the medical literature has repeatedly shown to be a possibility. Who would want to run such risk?” he asks. “Considering the importance of a correct diagnosis when dealing with a permanent condition that requires a life-long major dietetic change, the diagnostic approach should include both serology and biopsy. Of course, there could be single exceptions that should be left to the careful evaluation of experienced physicians on a case-by-case basis.”

Hard to Stomach

Many parents of kids with autism spectrum disorders (ASDs) are frustrated by their children’s troubling digestive symptoms. In January, Pediatrics, a journal of the American Academy of Pediatrics, published a consensus report on the evaluation, diagnosis and treatment of gastrointestinal disorders in people with ASDs. In its report, the multidisciplinary panel of experts from numerous medical schools and centers around the country wrote that GI disorders and related symptoms are commonly reported in people with ASDs but that causes, prevalence and best treatment are not yet well understood or defined. Rigorous research, such as double-blind, placebo-controlled trials, is scant. In light of this, the panel was unable to issue evidence-based recommendations but did make several statements.

Some of the “take-away messages” from the panel's report include: People with ASDs whose families report GI symptoms warrant a thorough GI evaluation; the communication challenges common in ASDs may lead to atypical signs of GI problems, including sleep disturbances and problem behaviors and that caregivers and health providers should be alert to these less usual signs; and integrating medical and behavioral treatments can be helpful in understanding pain as a potential “setting event” for behavior problems, as well as helpful for diagnosis and treatment.

The panel also wrote that not enough data currently exist to establish a causal role for GI problems—including intestinal inflammation, 'leaky gut' or food allergies—in people with ASDs.

As for the role of diet, such as the gluten-free, casein-free diet, in treating ASD, the panel wrote that anecdotal reports of improvements have not been refuted by rigorous research—or supported. Panelists acknowledged that a subgroup of people with ASDs may respond to the diet. They also recommended professional supervision of any special diet in order to prevent nutritional deficiencies. 

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