Biomarkers of delirium: Well evidenced or not?

Delirium is a common and serious acute neuropsychiatric syndrome characterized by inattention and global cognitive dysfunction. The etiologies of delirium are diverse, multifactorial, and often reflect the pathophysiologic consequences of an acute medical illness, medical complication, or drug intoxication. At present, the diagnosis of delirium depends on the presence of certain clinical features. Many recent studies have sought to identify biomarkers for delirium to predict its onset, severity, recovery rate, or prognosis. In this narrative review, we examine six approaches to identify serum biomarkers of delirium: serum chemistry, genes, neurotransmitters, inflammatory factors, serum cortisol levels, and end products of delirium. Moreover, we discuss the limitations of current research and the challenges of serum biomarker studies.