ICDSC

Overview

The Intensive Care Delirium Screening Checklist (ICDSC) was developed by Bergeron and colleagues as a checklist-style alternative to algorithmic delirium tools, designed to be completed by bedside ICU nurses from routine observation rather than a scripted cognitive test. In the original derivation cohort of 93 patients, the ICDSC showed a sensitivity of approximately 99 % and specificity of approximately 64 % against a psychiatric reference standard, and nurse-rated scores correlated strongly with an independent adjudicator's ratings (r = 0.924, p < 0.0005) ^[1].

Unlike the binary present/absent output of the CAM-ICU, the ICDSC produces a graded 0–8 total, which allows it to flag an intermediate subsyndromal delirium state — patients who meet some but not all criteria for delirium — rather than forcing every patient into a simple positive/negative bucket ^[2].

Item 1 (level of consciousness) is assessed first and acts as a gate: if the patient is unresponsive or responds only to intense, repeated stimulation (options A/B, roughly corresponding to RASS −4/−5), the remaining seven items cannot be meaningfully rated and the checklist is recorded as not assessable rather than scored as 0 ^[1]. Once the patient responds at least to mild-to-moderate stimulation (C, D, or E), all eight items are rated independently and summed.

Scale Items

Item	Description	Points
1. Altered level of consciousness	See gating table below (A–E)	0–1 or not assessable
2. Inattention	Difficulty following instructions or conversation; easily distracted by external stimuli; difficulty shifting focus	0 / 1
3. Disorientation	Any obvious mistake in time, place, or person	0 / 1
4. Hallucinations, delusions or psychosis	Unequivocal hallucinations or behaviour likely due to them; delusions; gross impairment in reality testing	0 / 1
5. Psychomotor agitation or retardation	Hyperactivity requiring extra sedatives/restraints, OR clinically noticeable psychomotor slowing	0 / 1
6. Inappropriate speech or mood	Disorganised/incoherent speech; inappropriate emotional display (apathetic or overly demanding); inappropriate comments	0 / 1
7. Sleep/wake cycle disturbance	Sleep < 4 h at night, or frequent nighttime awakening (excluding staff/noise-caused), or sleeping most of the day	0 / 1
8. Symptom fluctuation	Fluctuation of any of items 1–7 over the preceding 24 hours	0 / 1

Item 1 — Level of Consciousness (Gating)

Item 1 uses the original sedation-scale-agnostic A–E wording. Approximate RASS equivalence is shown for orientation only — ICDSC does not require RASS to be scored.

Option	Description	≈ RASS	Points
A	No response to stimulation (coma)	−4 / −5	Not assessable — assessment halts
B	Response only to intense/repeated stimulation (stupor)	−4 / −5	Not assessable — assessment halts
C	Response to mild-to-moderate stimulation (drowsy / sopor)	−1 to −3	1
D	Normal wakefulness	0	0
E	Exaggerated response to normal stimulation (agitation)	+1 to +4	1

Score Interpretation

Total Score	Interpretation
Not assessable	LOC = A or B (coma/stupor) — assessment cannot be completed
0	No delirium
1–3	Subsyndromal delirium — intermediate state, worse outcomes than 0 but not diagnostic of delirium; increased monitoring recommended
≥ 4	Delirium present

The subsyndromal delirium category was characterised by Ouimet and colleagues, who followed a mixed medical-surgical ICU cohort and found ICU mortality of 2.4 % among patients scoring 0, 10.6 % among those scoring 1–3, and 15.9 % among those scoring ≥ 4, with ICU length of stay increasing across the same gradient ^[2]. This dose-response relationship is the main evidence for treating 1–3 as a clinically meaningful intermediate state rather than simply "negative."

Above the ≥ 4 threshold, the ICDSC indicates the presence of delirium only — it was not designed and has not been validated to grade delirium severity beyond that point.

Assessment Procedure

1. Rate item 1 (level of consciousness) first, at the bedside.
2. If item 1 is A or B, stop — record the assessment as not assessable and reassess once the patient responds at least to mild-to-moderate stimulation.
3. If item 1 is C, D, or E, rate items 2–4 from a focused bedside evaluation, and items 5–8 from observations made across the whole shift; items 7 and 8 specifically refer to the preceding 24 hours.
4. Sum all eight items (maximum 8) and classify using the interpretation table above.
5. Repeat once per 8-hour nursing shift, or at least once every 24 hours, per current ICU delirium-monitoring guidance ^[3].

Scientific Validity & Limitations

A 2012 systematic review and meta-analysis pooling multiple validation cohorts found that both the ICDSC and the CAM-ICU have imperfect, and broadly comparable, diagnostic accuracy in routine use, with neither tool demonstrating clear superiority over the other ^[4]. The lower specificity observed in some cohorts (in contrast to the near-ceiling ~99 % sensitivity / ~64 % specificity of the original derivation study ^[1]) has prompted re-examination of the ≥ 4 cutoff itself.

A 2018 re-evaluation by Boettger and colleagues, benchmarked against DSM-IV-TR diagnosis, reported sensitivity of 61.5 % and specificity of 95.2 % at the standard ≥ 4 cutoff, but sensitivity of 83 % and specificity of 85.5 % at a lower cutoff of ≥ 3, arguing that the conventional ≥ 4 threshold under-diagnoses delirium in some populations ^[5]. This is a secondary re-evaluation in a specific cohort, not a revision adopted by the original authors or by current guidelines — Scores2Go implements the original, guideline-endorsed ≥ 4 threshold, not the proposed ≥ 3 cutoff.

A 2019 prospective cohort study by Boßelmann and colleagues found that ICDSC specificity dropped to roughly 55 % in aphasic ICU patients — items 2, 3, 4, and 6 are difficult to rate reliably when a patient cannot communicate for reasons unrelated to delirium — and proposed a higher cutoff of ≥ 5 specifically for that subgroup ^[6]. This subgroup-specific adjustment is likewise not implemented here; clinicians assessing aphasic patients should interpret borderline ICDSC scores with this caveat in mind.

Other well-documented limitations, independent of any single study:

• Unassessability in deep sedation/coma: at LOC A/B the checklist cannot be scored at all — a coverage gap rather than a false result, analogous to the CAM-ICU's inability to assess patients at RASS −4/−5.
• Reliance on nursing observation across a shift: items 5–8 are rated from behaviour over several hours rather than a single structured test, which makes the checklist fast to complete but dependent on the observing nurse's attentiveness and continuity of care.
• Language and communication barriers: beyond aphasia specifically, patients with limited language proficiency, hearing impairment, or heavy sedation-related dysarthria may score falsely high on the inattention, disorientation, and speech items.
• Original validation was in a single, relatively small cohort: the ~99 %/~64 % sensitivity/specificity figures come from 93 patients at one centre ^[1]; subsequent multicentre and meta-analytic data show more variable, generally lower accuracy ^[4].

A validated German-language version of the ICDSC exists ^[7]. Both the ICDSC and CAM-ICU remain endorsed by the 2018 Society of Critical Care Medicine PADIS guidelines as validated delirium-monitoring tools for at-least-once-per-shift ICU use, with the choice between them left to institutional preference ^[3].

Literature

1. Bergeron N, Dubois M-J, Dumont M, Dial S, Skrobik Y. Intensive Care Delirium Screening Checklist: evaluation of a new screening tool. Intensive Care Med. 2001;27(5):859–864. doi:10.1007/s001340100909
2. Ouimet S, Riker R, Bergeron N, Cossette M, Kavanagh B, Skrobik Y. Subsyndromal delirium in the ICU: evidence for a disease spectrum. Intensive Care Med. 2007;33(6):1007–1013. doi:10.1007/s00134-007-0618-y
3. Devlin JW, Skrobik Y, Gélinas C, et al. Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU. Crit Care Med. 2018;46(9):e825–e873. doi:10.1097/CCM.0000000000003299
4. Gusmao-Flores D, Salluh JIF, Chalhub RÁ, Quarantini LC. The confusion assessment method for the intensive care unit (CAM-ICU) and intensive care delirium screening checklist (ICDSC) for the diagnosis of delirium: a systematic review and meta-analysis of clinical studies. Crit Care. 2012;16(4):R115. doi:10.1186/cc11407
5. Boettger S, Garcia Nuñez D, Meyer R, et al. Screening for delirium with the Intensive Care Delirium Screening Checklist (ICDSC): a re-evaluation of the threshold for delirium. Swiss Med Wkly. 2018;148:w14597. doi:10.4414/smw.2018.14597
6. Boßelmann C, et al. Delirium Screening in Aphasic Patients With the Intensive Care Delirium Screening Checklist (ICDSC): A Prospective Cohort Study. Front Neurol. 2019;10:1198.
7. Radtke FM, Franck M, Oppermann S, et al. Die Intensive Care Delirium Screening Checklist (ICDSC) – Richtlinienkonforme Übersetzung und Validierung einer intensivmedizinischen Delirium-Checkliste. Anästhesiol Intensivmed Notfallmed Schmerzther. 2009;44(2):80–86.