This patient most likely has urinary tract infection based on the symptoms and positive leukocyte esterase and nitrites. The best next step is to assess vital signs and obtain urine culture and sensitivities prior to administering antibiotics. Urine culture and sensitivity helps to identify pathogenic bacteria and their antibiotic sensitivity in patients with presumed urinary tract infection. Placement of the urinary catheter may be appropriate if the patient has difficulty voiding. Fluid administration is an appropriate next step if the patient has signs of dehydration. Urinary tract infection is a common cause of acute mental status change in elderly patients—a head CT may be ordered, but it would be unlikely since there is a reasonable explanation for the woman’s mental status.