You can determine if a target creature is currently under the influence of any outside source. After the casting is completed, you are able to determine whether a creature is currently poisoned, diseased, cursed, transformed, or has any magical effects or enchantments on it. It can also be used to determine whether a target is a shapechanger. Furthermore, with a successful Intelligence (Arcane) check, you can determine whether the influence is a disease or poison (DC 10), or an enchantment, curse, or other magical effect (DC 15). If you exceed this DC by 5 or more, you may be able to determine specifically what the influence is and possible means to cure or remove it (at the DM's discretion). 

An unwilling target can defy the delving with a successful contest of wills; i.e. a successful Wisdom saving throw. If this saving throw is successful, the caster is unable to determine whether the target has any outside influence at all.