it s not that simple dear. Schizophrenia is not a single disease it s a syndrome with variable presentations. People suffering may appear very normal and functioning well or can be totally disorganized. hallucinations, illusions are common but not the only symptom and are not required to be diagnosed from suffering from the illness. Schizophrenia is not diagnosed by any test. It s a clinical diagnosis by a psychiatrist... again not by his own set of rules but by application of criteria. Usually that of the W.H.O. i.e. ICD - 10 criteria or the DSM-IV criteria of the American Psychiatric Association. A psychiatrist applies his clinical knowledge from history collected from patient as well as informants, duration of symptoms, nature of symptoms, rules out other possible medical causes and comes to the conclusion. Does it sound simple to you... Not really