title: Subsyndromal delirium in the intensive care setting: Phenomenological characteristics and discrimination of subsyndromal delirium versus no and full-syndromal delirium.
abstract: OBJECTIVE
  Similar to delirium, its subsyndromal form has been recognized as the cause of diverse adverse outcomes. Nonetheless, the nature of this subsyndromal delirium remains vastly understudied. Therefore, in the following, we evaluate the phenomenological characteristics of this syndrome versus no and full-syndromal delirium.
  
  
  METHODS
  In this prospective cohort study, we evaluated the Delirium Rating Scale-Revised, 1998 (DRS-R-98) versus the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision (DSM-IV-TR) diagnostic criteria and examined the diagnosis of delirium with respect to phenomenological distinctions in the intensive care setting.
  
  
  RESULTS
  Out of 289 patients, 36 with subsyndromal delirium versus 86 with full-syndromal and 167 without delirium were identified. Agreement with respect to the DSM-IV-TR diagnosis of delirium was perfect. The most common subtype in those with subsyndromal delirium was hypoactive, in contrast to mixed subtype in those with full-syndromal delirium versus no motor alterations in those without delirium. By presence and severity of delirium symptoms, subsyndromal delirium was intermediate. The ability of the DRS-R-98 items to discriminate between either form of delirium was substantial. Between subsyndromal and no delirium, the cognitive domain and sleep-wake cycle were more impaired and allowed a distinction with no delirium. Further, between full- and subsyndromal delirium, the prevalence and severity of individual DRS-R-98 items were greater. Although the differences between these two forms of delirium was substantial, the items were not very specific, indicating that the phenomenology of subsyndromal delirium is closer to full-syndromal delirium.
  
  
  CONCLUSIONS
  Phenomenologically, subsyndromal delirium was found to be distinct from and intermediate between no delirium and full-syndromal delirium. Moreover, the greater proximity to full-syndromal delirium indicated that subsyndromal delirium represents an identifiable subform of full-syndromal delirium.
authors.affiliation: Department of Psychiatry and Psychotherapy,University Hospital Zurich, University of Zurich,Switzerland.
authors.forename: Soenke
authors.initials: S
authors.lastname: Boettger
authors.affiliation: Department of Psychiatry and Psychotherapy,University Hospital Zurich, University of Zurich,Switzerland.
authors.forename: David Garcia
authors.initials: DG
authors.lastname: Nuñez
authors.affiliation: Institute for Regenerative Medicine, University of Zurich,Schlieren,Switzerland.
authors.forename: Rafael
authors.initials: R
authors.lastname: Meyer
authors.affiliation: Department of Psychiatry and Psychotherapy,University Hospital Zurich, University of Zurich,Switzerland.
authors.forename: André
authors.initials: A
authors.lastname: Richter
authors.affiliation: Inselspital, University Hospital Bern,Directorate of Nursing/MTT,Bern,Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Schubert
authors.affiliation: Department of Psychiatry and Psychotherapy,University Hospital Zurich, University of Zurich,Switzerland.
authors.forename: Josef
authors.initials: J
authors.lastname: Jenewein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003693:Delirium / Q000145:classification* / Q000175:diagnosis* / Q000503:physiopathology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007362:Intensive Care Units / Q000458:organization & administration; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D015995:Prevalence; D011446:Prospective Studies; D013557:Switzerland
keywords: 
                 Diagnostic and Statistical Manual of Mental Disorders
              ; 1998 (DRS–R–98); 4th ed.; Delirium; Delirium Rating Scale–Revised; Full-syndromal; Intensive care unit (ICU); Phenomenology; Subsyndromal; Text Revision (DSM–IV–TR)