*Yоur friend brings his 85 y/о fаther tо your prаctice becаuse he is having new onset trouble remembering things and being oriented. He talked to him 3 days ago and he was fine. But, today, he found him in the living room with his pajamas on looking for his car keys. He has a fever today of 102F. Past medical history consists of arthritis, hypertension and BPH. Which of the following tests would be a easy way to tell what could be going on?