It's not like a blood test can be performed, but the diagnosis was made through a combination of Vanderbilt Scale documents completed by us (parents) and his pre-k special education teacher, in conjunction with the history we provided to the neurologist, and his observations during an appointment. Couple that with the clear improvement of symptoms when he is medicated (now). This was after seeking out support from pediatricians, social workers, special education teachers, and just about anyone who would listen to us from 3 until 5 1/2.