It is not that easy to tell the difference between true NPD and peculiarities of behavior. It is impossible to tell if the person is mentally ill with the help of physical tests or exams. Most people who face this problem reject any sort of help and treatment as they believe they’re okay while others have problems. Until the problem gets over the patient’s life, he or she does not understand its threats.The specialist will need to observe a medical history along with the biography to make a final conclusion. He will check some reactions to irritating factors. In case a professional notice all symptoms associated with NPD, the conclusion can be made.