The goal of this project is to develop a screening tool for Autism Spectrum Disorder (ASD). These researcher's preliminary work using microarray plates, identified significantly lower levels of Nicotinamide Adenine Dinucleotide (NADH) in lymphoblasts generated in the presence of tryptophan in patients with ASD when compared to controls. The proposal for the current project is to first validate the preliminary findings using a cohort of 50 additional ASD patients and 50 additional controls, and to utilize the same metabolic profiling approach using leukocytes from fresh blood samples to determine if ASD can be quickly and reliably distinguished from controls. If the preliminary findings in lymphoblasts are confirmed in leukocytes, we would be able to develop a reliable, easy to perform, inexpensive laboratory test which could provide a diagnosis in about 4-5 days. Such a test could represent the first biochemical screening test for ASDs.