Discordance between ICDSC and CAM-ICU-7 as measures of delirium severity in the ICU

Karla D. Krewulak PhD and Kirsten M. Fiest PhD
Department of Critical Care Medicine, University of Calgary, Calgary, AB, Canada

Determination of delirium presence or absence may no longer be sufficient when tools exist to measure a delirium score which many be used to estimate delirium severity. Measurement of delirium severity has been identified as important for the advancement of both the science of delirium measurement and clinical care. For example, score-based delirium detection may identify the early onset of delirium, prompting earlier provision of delirium prevention and management strategies. There are 42 instruments in the literature for rating delirium and 14 for delirium severity (Jones et al. 2018) yet little is known about how they compare. Understanding how delirium severity measurements compare will help investigators determine if data can be harmonized across delirium studies, which has the potential to further advance delirium knowledge.

The two most commonly used delirium screening tools in the intensive care unit (ICU) are the Intensive Care Delirium Screening Checklist (ICDSC; Bergeron et al. 2001) and the Confusion Assessment Method for the ICU (CAM-ICU; Ely et al. 2001). The ICDSC is score-based, with scores categorized as 0 (no delirium), 1-3 (subsyndromal delirium), and 4-8 (delirium). Recently, a scoring algorithm was applied to the CAM-ICU items (Khan et al. 2017) to create the CAM-ICU-7. CAM-ICU-7 scores can be categorized as 0 (no delirium), 1-2 (subsyndromal delirium), 3-5 (mild to moderate), and 6-7 (severe delirium). The aim of a current study was to compare the ICDSC and CAM-ICU-7 as measures of delirium severity and identify associations with short terms outcomes in critically ill adults (Krewulak et al. 2020).

In this cross-sectional study, 218 critically ill adults underwent 641 paired ICDSC and CAM-ICU-7 assessments. The results of this study suggest that comparisons between the ICDSC and CAM-ICU-7 as measures of subsyndromal delirium (i.e., ICDSC score 1-3 and CAM-ICU-7 score 1-2) and delirium (i.e., ICDSC score 4-8 and CAM-ICU-7 score 3-7) are imperfect. The agreements between ICDSC and CAM-ICU-7 as a measure of subsyndromal and overall delirium were demonstrated to be fair (kappa=0.21) and moderate (kappa=0.51), respectively. However, there is a significant positive correlation between ICDSC and CAM-ICU-7 when considering the range of ICDSC (0-8) and CAM-ICU-7 (0-7) scores. In other words, when an ICDSC score increases, the CAM-ICU-7 score would likely also increase. This was further demonstrated when an increased score on either tool was associated with a longer duration of mechanical ventilation and an increased median length of ICU stay. Despite the imperfect agreement between the ICDSC and CAM-ICU-7 scores as measures of delirium severity, there is a similar association between ICDSC and CAM-ICU-7 scores and short term outcomes.

Graph for Discordance between ICDSC and CAM-ICU-7 blog post

The results of the study suggest it may not be possible for ICDSC and CAM-ICU-7 to be harmonized as measures of delirium severity. This may not be surprising, given their differing administration procedures (ICDSC: 12-hour observation; CAM-ICU-7: point assessment) and symptoms of delirium each measures. For example, the ICDSC measures disturbances in the sleep wake cycle, a common issue with ICU patients, but the CAM-ICU-7 does not). Moreover, the ICDSC has not been validated as a measurement of delirium severity. Further studies are needed to harmonize the measurement of delirium severity using the ICDSC with delirium severity measures validated for use in ICU patients. Adequately powered studies are needed to further evaluate the spectrum of ICDSC and CAM-ICU-7 scores.

References

Bergeron N, Dubois MJ, Dumont M, Dial S, Skrobik Y. Intensive Care Delirium Screening Checklist: evaluation of a new screening tool. Intensive Care Med. 2001 May;27(5):859-64. doi: 10.1007/s001340100909. PMID: 11430542.

Ely EW, Inouye SK, Bernard GR, Gordon S, Francis J, May L, Truman B, Speroff T, Gautam S, Margolin R, Hart RP, Dittus R. Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA. 2001 Dec 5;286(21):2703-10. doi: 10.1001/jama.286.21.2703. PMID: 11730446.

Ely EW, Margolin R, Francis J, May L, Truman B, Dittus R, Speroff T, Gautam S, Bernard GR, Inouye SK. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Crit Care Med. 2001 Jul;29(7):1370-9. doi: 10.1097/00003246-200107000-00012. PMID: 11445689.

Jones RN, Cizginer S, Pavlech L, et al. Assessment of Instruments for Measurement of Delirium Severity: A Systematic Review. JAMA Intern Med. 2019;179(2):231–239. doi:10.1001/jamainternmed.2018.6975

Khan BA, Perkins AJ, Gao S, Hui SL, Campbell NL, Farber MO, Chlan LL, Boustani MA. The Confusion Assessment Method for the ICU-7 Delirium Severity Scale: A Novel Delirium Severity Instrument for Use in the ICU. Crit Care Med. 2017 May;45(5):851-857. doi: 10.1097/CCM.0000000000002368. PMID: 28263192; PMCID: PMC5392153.

Krewulak KD, Rosgen BK, Ely EW, Stelfox HT, Fiest KM. The CAM-ICU-7 and ICDSC as measures of delirium severity in critically ill adult patients. PLoS One. 2020 Nov 16;15(11):e0242378. doi: 10.1371/journal.pone.0242378. PMID: 33196655; PMCID: PMC7668609.

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One Comment

  1. Thanks for this interesting post! I am more optimistic that the ICDSC and CAM-ICU-7 can be harmonized to some degree. Krewulack et al report a scale score correlation of the two of .59 — which is not super high but nonetheless substantial — and some of the individual items are very similar (e.g., both score altered level of consciousness on the basis of RASS; both score inattention with SAVEAHAART). It is very clear from this work that the thresholds used on the scale scores for no/subsyndromal/delirium with ICDSC vs thresholds for none/subsyndromal/mild/severe with CAM-ICU-7 are not compatible.

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