Three methods are used to make a diagnosis: medical history, examination and laboratory-instrumental analysis.

With advances in modern medical technology, laboratory instrumental analysis is gaining increasing importance and trust, while classical methods are neglected: a thorough review of the medical history and a detailed examination.

To point out the significance of making a timely and correct diagnosis.

Report the case of 47 year old female patient with no previous psychiatric history. Her symptoms appeared suddenly in the morning, developed a clinical picture with psychotic symptoms. A CT scan of her brain, was normal findings. She went to a neurologist, who produced an orderly neurological report and recommended a screening test for psychoactive substances (PAS). The test was positive for heroin, morphine and benzodiazepine. Since she is disoriented and has incoherent speech and neologisms, she was hospitalised at the Psychiatry hospital. Abuse of the PAS was excluded because she used analgesic contains codeine. On the seventh day of her stay a CT scan of her brain was made and showed a large ischaemic lesion in the left temporoparietal area.

Laboratory-instrumental analysis is not without objective and subjective errors and must not guide the diagnosis without a sufficient clinical basis, and it must be preceded by a review of the medical history and an examination. A timely and correct diagnosis is important in order to provide adequate therapeutic treatment to a patient as soon as possible and in order to avoid needless hospitalisation in the psychiatry ward.