Urine opiate screening: false-positive result with levofloxacin

Abstract

96-year-old woman with moderate to severe dementia was admitted in acute delirium. According to her next of kin, the patient had been reporting generalized weakness for the last few days, and her appetite had decreased. The day before admission, she began having visual and auditory hallucinations. At the time of admission, the patient was delirious and in moderate respiratory distress, with rapid shallow breathing and an oxygen saturation level of 88% on room air. Bilateral basilar crackles on inspiration and right-sided rhonchi were heard on auscultation. Her blood pressure was 140/75 mm Hg, her heart rate was 110 beats/min with a normal sinus rhythm, and her temperature was 37.2°C. The initial results of imaging and laboratory investigation were all normal, including a computed tomography scan of the head, chest radiographs, complete blood count with differential count, thyroid function tests, and serum levels of electrolytes, liver enzymes, amylase, lipase, cardiac enzymes, vitamin B12, erythrocyte folate, iron, ammonia and alcohol. The results of her blood gas tests were normal except for a partial pressure of oxygen of 60. The results of Gram staining and culture of blood, urine and sputum samples were negative for bacteria. The results of urine toxicology screening were negative for opiates and benzodiazepines. Twelve-lead electrocardiography did not show evidence of acute coronary syndrome or arrhythmias. Empirical treatment with broad-spectrum antibiotics, including piperacillin‐ tazobactam and vancomycin, was started for suspected aspiration pneumonia. Three days later, the patient’s mental status and respiratory distress were worse. Levofloxacin was added to the treatment to provide coverage for atypical bacteria. A neurology consultation was obtained to rule out a neurologic cause for the patient’s worsening mental status. Magnetic resonance imaging of the brain and electroencephalography were done, but neither showed acute neurologic pathology. We diagnosed metabolic