Methods for diagnosing pervasive development disorders, dysautonomia and other neurological conditions

A method for diagnosing an individual as having or likely to develop Autism, the method comprising:

• obtaining a stool sample from the individual;
• analyzing the stool sample to detect the presence or absence of one or more antigens associated with two or more pathogens, wherein the two or more pathogens comprise Helicobacter pylori, Cryptosporidium, Entamoeba histolytica, Giardia, Rotavirus, Adenovirus, Cyclospora, Microsporidia, or Isospora Belli;
• analyzing the stool sample to detect the level of chymotrypsin present;
• diagnosing the individual as having or likely to develop autism based on the presence of the one or more antigens associated with the two or more different pathogens and an abnormally low level of chymotrypsin in the stool sample.

A method of screening an individual for risk of developing Autism, the method comprising:

• obtaining a stool sample from the individual;
• analyzing the stool sample to detect the presence or absence of one or more antigens associated with two or more pathogens, wherein the two or more pathogens comprise Helicobacter pylori, Cryptosporidium, Entamoeba histolytica, Giardia, Rotavirus, Adenovirus, Cyclospora, Microsporidia, or Isospora belli;
• analyzing the stool sample to detect the level of chymotrypsin present;
• identifying the individual as having an increased risk of developing Autism based on the presence of the one or more antigens associated with the two or more different pathogens and an abnormally low level of chymotrypsin in the stool sample.