Well you can do blood allergy testing called RAST to see if he has a true gluten allergy, however gluten "allergies" are mostly intolerance as far as I know. Also both RAST and traditional skin prick tests are not considered definitive, you then have to do an "oral challenge" (which is to say eat it and see if there is a reaction).

There is testing for celiac disease but I think it involved biopsy.

However before I go any farther I want to make one thing clear, all of the therapy for autism excluding drugs is SAFE and BENEFICIAL for all children -autistic or not. Really most "normal" children would become "gifted" if they received the kinds of attentive physical and mental therapies given to autistic children. Most of these therapies are presented as play and most children are quite happy to do them.

Eliminating wheat is pointless unless you eliminate ALL sources of gluten.

http://autism.about.com/od/whatisautism/a/screendx.htm
Because autism cannot be diagnosed with a medical test, screening and diagnosis involves interviews, observation and evaluations. Even when a professional provides an opinion, the opinion may be couched in such terms as "it LOOKS like a pervasive developmental disorder, but your child doesn't have all the symptoms of autism." While this kind of uncertainty can be extemely frustrating, it's sometimes unavoidable -- and even clearcut autism diagnoses can change over time.

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NOTE: This link is having an autism "WEBNAR" (web seminar) tomorrow night. I don' t know anything about this group or the reliability of the people running this but it may be helpful:
http://www.autism-pdd.net/diagnosing-autism.html
The diagnosing autism is made when specified number of characteristics listed in the DSM-IV (Diagnostic And Statistical Manual Of Mental DisordersDSM-IV ) are present, in ranges inappropriate for the child's age. Autism diagnosis usually occurs between the ages three and five. The autism prognosis is consistent across a broad range of studies - about 2% will attain normal functioning, with perhaps 40% labeled high functioning autistic.

http://www.autism-pdd.net/checklist.html
DIAGNOSTIC CRITERIA FOR 299.00 AUTISTIC DISORDER
A. A total of six (or more) items from (1), (2), and (3), with at
least two from (1), and one each from (2) and (3)

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http://www.autism.ca/whataut.htm
At present, physicians, psychiatrists and psychologists rely on the behavioural criteria outlined in the Diagnostic and Statistical Manual - Fourth Edition (DSM-IV) when diagnosing autism. Generally, autistic individuals display the following:

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http://www.yourguidetoautism.com/how-is-autism-diagnosed.html
Researchers have found that early diagnosis of autism is very important. The earlier a child is diagnosed with autism, the earlier he or she can start getting help from interventions and therapies.

Unfortunately, there aren’t any medical tests that can be used to diagnose autism. In order to be diagnosed accurately with autism, a child’s communication, behavior, and developmental levels have to be observed.

It is important that these observations are made by a medical specialist or someone who has experience in diagnosing autism.

Ideally, a child should be evaluated by a team of professionals which may include a neurologist, psychologist, developmental pediatrician, speech and language therapist, learning consultant, or other professionals knowledgeable about autism.

Because people with other disorders may have similar behaviors as people with autism, a doctor may have to do various medical tests to rule out other possible causes.

In the US, there is a manual called the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) that is published by the American Psychiatric Association that medical professionals can use to help diagnose autism.

Some other tools that have been developed to help doctors and other professionals make an accurate diagnosis of autism include: CHAT (Checklist for Autism in Toddlers), CARS (Childhood Autism Rating Scale), PIA (Parent Interviews for Autism), GARS (Gilliam Autism Rating Scale) and BRIAC (Behavior Rating Instrument for Autistic and other Atypical Children).
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http://autism.about.com/od/medicalissuesandautis1/a/whodxasd.htm
Why Your Own Pediatrician May Not Be Able to Help in Diagnosing Autism
In theory, your own pediatrician should be able to pinpoint red flag behaviors or challenges that suggest autism. But your own pediatrician only sees your child once a year (if you're lucky) -- or when your child is sick. And even now, with so much awareness of autism spectrum disorders, most pediatricians have little knowledge of how to screen for subtle developmental concerns. What's more, since pediatricians see so many children, most of whom do just fine in the long run, they generally tend to take a "wait and see" approach to issues that are not medically dangerous.

If you do take your child to your own pediatrician, and that doctor reassures you that there are no issues of concern, you may decide to stop right there. But if you continue to have concerns, it can't possibly hurt to take the next step by asking your pediatrician to refer you to an autism specialist. The best that could happen is that the specialist finds no issues. The worst that could happen is that the specialist pinpoints issues that can be addressed right away.
What Is an "Autism Specialist?"
Before about 1990, autism was a rare disorder. Today, it's relatively common. But there are still very few medical professionals who are specifically trained to diagnose and/or treat autism. As a result, the people who are best qualified to diagnose children with autism are those professionals who have had the most experience in doing so -- and those professionals may have a wide range of titles. These may include:

* Developmental Pediatrician
* Pediatric Neurologist
* Child Psychologist
* Child Psychiatrist

In addition to these medical professionals, there are many therapists who can take part in a multidisciplinary evaluation of your child. While these people are not medically trained, they may know as much or more about autism as a highly trained doctor -- simply because they spend so much time around autistic people. These individuals may include:

* Speech Therapist
* Occupational Therapist
* Physical Therapist
* Social Worker

Because there is no medical test for autism, diagnosis is based on a combination of parent interviews, non-medical tests, observation -- and personal judgement. That's why experience, as much as training, can be critical in providing a meaningful diagnosis.
Who Should Diagnose My Child?
With so many possible options, who is the right person to diagnose your child? The answer depends, to a large degree, upon who is available. Depending upon where you live, you may find that there is a long wait to see a developmental pediatrician -- while you can get in to see an experienced child psychologist almost right away.

Another issue to consider is money. You might also find that, while a neurologist is covered by insurance, a psychologist is not. In some states, early intervention programs provide free multidisciplinary evaluations; in other states, such evaluations may be hard to access.

A word of advice from highly experienced psychologist Dr. Robert Naseef: Even if your initial diagnosis comes from a psychologist, it may be worth your while to also consult an M.D. The reason is more political than medical: without an M.D. behind your child's diagnosis, says Naseef, your local school district may not provide an appropriate array of services.

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http://www.musckids.com/news/autism.htm
The absence of a test for autism further hinders the disorder's diagnosis. Autism can�t be detected through blood work or an MRI, and many of the disorder�s symptoms overlap with those of other developmental disorders.

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http://www.health.state.ny.us/community/infants_children/early_intervention/disorders/autism/health.htm
Recommendations

1. Magnetic resonance imaging (MRI) scans may be useful in certain clinical situations in assessing children with autism when there is heightened concern about focal neurological problems, such as seizures. [D2]

2. MRI scans may be useful in assessing some children at risk for neurological problems, such as children with a history of perinatal problems (medical problems that occurred around the time of birth). [D2]

3. The use of MRI scans is not recommended in the routine assessment of children with possible autism. [C]

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http://www.autismweb.com/diet.htm
Medical tests can determine if your child has a sensitivity or an allergy to gluten, casein and other foods such as eggs, nuts and soybeans. Any pediatrician or a physician from the DAN! (Defeat Autism Now!) list can order these tests before you begin the diet.

Before you consider a change in your child's diet, consult with a physician and nutritionist to make sure you are providing an adequate diet and nutritional supplements, if necessary. Also, please read any of the books and web sites about the diet (listed below).

Some advocates of dietary intervention suggest removing one food from the diet at a time, so you will know which food was causing a problem. It also is helpful to ask people who do not know about the dietary change if they see any improvement after a few weeks.

It's often suggested to remove milk first because the body will clear itself of milk/casein the quickest. Gluten may be removed a month after the elimination of milk. It may take up to six months on a gluten-free diet for the body to rid itself of all gluten. That is why most advocates suggest giving the diet a trial of six month

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http://autism.healingthresholds.com/therapy/gluten-free-diet#work
One well-controlled study focused on children with autism who had abnormally high protein by-products in their urine, and therefore were more likely to be sensitive to casein and gluten (see What is the theory behind it?). One group of these children was fed a strict casein- and gluten-free diet for 12 months. This group had significantly fewer autistic symptoms than the remaining children, who were not fed this diet (8). Another well-controlled study of casein- and gluten-free diets focused on children with autism regardless of the level of protein by-products in their urine (9). Overall, the study found no significant differences in behavior between children on the elimination diet and children on regular diets, although individual parents reported behavioral improvements (9). This overall lack of effect in the second study could be because the elimination diet only lasted 6 weeks, or because the children were not pre-selected according to the level of protein by-products in their urine.

Regardless, in both cases, the tested diets were casein- and gluten-free, so it is not clear whether it was the elimination of casein, gluten, or both that resulted in any improvements. A third study that did examine the effect of a gluten-free diet on the behavior of children with autism did not compare children on the elimination diet with children not on the diet (10). Therefore, even though there were improvements seen in the behavior of children on the diet, these may also have occurred over the 5 months of the study without the elimination diet.

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http://paleodiet.com/autism/#test
Testing

* Antibody Assay Laboratory in Santa Ana, CA had Urinary Polypeptides testing available in the US for research use for $90. To find the page you have to select from the combo box at the top of the page. The test must be authorized by a doctor. This test was developed with the help of Paul Shattock. It is useful for: autism, ADD, ADHD, dyslexia and obsessive compulsive disorder. Also see Intestinal Permeability Evaluation which is on "Casein and Gliadin Antibodies: A novel way to detect intestinal permeability".

* Sage Systems has a Comprehensive ELISA Allergy Test and Treatment for the Relief of Chronic Illness. See their page on Autism and its relationship to delayed food allergies.

* The Great Plains Laboratory for Health, Nutrition, and Metabolism is Dr. William Shaw's site. They specialize in urine organic acid testing. Much information is at this new site. Another site: The Great Plains Laboratory.

* Alletess Medical Laboratory is the lab used by Dr. Cade. His study participants get the "gluten and casein screen" test done, which looks for anti-gliaden and anti-casein antibodies.

* Great Smokies Diagnostic Laboratory has a page on What is Functional Medicine? which describes laboratory tests that allow practitioners to understand a patient's functional status.

* BodyBio has tests for Blood Chemistry and Fatty Acid. BodyBio believes in using nutrition on functions and disorders. Included in each BioCell™ Report are: what foods to seek, foods to avoid, medication intolerances, vitamins needed, vitamins not needed, imbalances in major body organs.

* The former medical director of Immuno Labs now has his own business at Dr. Braly's Allergy Relief, the Natural Way. Test kits from York Nutritional Laboratories are used. See FoodSCAN which does not require a blood draw.

* The largest outfit that does ELISA testing for food allergy/intolerance is in Fort Lauderdale. The parent company site Immuno Laboratories is oriented towards doctors. Then they have a consumer site: Better Health USA Food Allergy Relief Center.

* And for those in the UK: York Nutritional Laboratory.

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Autism Research Unit Urine Peptide Testing
http://www.healthboards.com/autism/488.html

http://yourtotalhealth.ivillage.com/gluten-intolerance.html?pageNum=7#7
Several diagnostic methods are available when gluten intolerance (celiac disease) is suspected. Usually a diagnosis is sought when the symptoms of malabsorption and malnutrition have been observed. There are two major tests available to physicians for the diagnosis of gluten intolerance:

*
Biopsy of the small intestine. This is considered the best test for diagnosing gluten intolerance because of its high degree of accuracy. The test involves a physician obtaining a sample of the intestinal lining through a procedure known as an esophagogastroduodenoscopy (EGD). The EGD procedure, a type of upper endoscopy, uses a small camera, inserted down the throat on a flexible tube, to navigate down to the intestinal lining and remove a small sample. The patient typically receives general anesthesia or a sedative. A pathologist will then examine the sample to check for characteristics that indicate gluten intolerance, such as a loss of villi (protrusions found on the lining of the small intestine that absorb nutrients into the bloodstream).

*
Antibody test. A blood test for the presence of certain antibodies – specifically, antibodies to endomysium (bands of connective tissue spread among muscular fibers) and transglutaminase (a substance that repairs injured or inflamed tissue). These antibodies form when the immune system reacts to the presence of substances it views as threatening. When certain specific antibodies are present in the bloodstream, an individual has a greater than 95 percent chance of having gluten intolerance.

Though not able to diagnose gluten intolerance directly, there are also several types of blood tests available for detecting the related malnutrition and vitamin deficiencies. These tests will usually show some type of a reduction in blood protein levels or iron-deficiency anemia in gluten-intolerant individuals.

Because gluten intolerance is a hereditary disease, the family members of an individual who has gluten intolerance may wish to be tested for the disease.

Because of recent research that has shown a close relationship between gluten intolerance and the development of osteoporosis, some physicians are screening patients diagnosed with osteoporosis for gluten intolerance as well. And people who are diagnosed with gluten intolerance may be screened for osteoporosis with a bone density test such as a DEXA scan, a type of x-ray.