Q: Which one test may help in distinguishing Epilepsy from a psychogenic non-epileptic seizure?

Answer:  A prolactin level

A high blood prolactin level within the first 20 minutes following a seizure may be useful to differentiate an epileptic seizure as opposed to psychogenic non-epileptic seizure.

1.  Luef, G (October 2010). "Hormonal alterations following seizures.". Epilepsy & behavior : E&B 19 (2): 131–3.

2. Ahmad S, Beckett MW (2004). "Value of serum prolactin in the management of syncope". Emergency medicine journal : EMJ 21 (2): e3