Canavan disease can be diagnosed with a blood test. A person with Canavan disease has no detectable amounts of ASPA, and the low level of this enzyme in a person's blood is characteristic of the disease.

The NAA that builds up in the body of a person with Canavan disease is excreted in the urine. Individuals without Canavan disease have no detectable amounts of NAA in their urine. The presence of NAA in the urine of an individual is sufficient to make the diagnosis of Canavan disease.

Prenatal diagnosis for Canavan disease is available using samples collected with procedures called chorionic villus sampling (CVS) or amniocentesis, which are performed early in pregnancy.