Measuring delirium severity — and comparing scales
Grading how severe delirium is and tracking change over time can support prognosis and research. This page compares the main severity instruments and links to the NIDUS research crosswalk for harmonising scores between studies.
The principal severity instruments
| Instrument | Items | Range | Best suited to | Reference |
|---|---|---|---|---|
| MDAS Memorial Delirium Assessment Scale | 10 | 0–30 | Palliative / oncology; repeated measures | Details |
| DRS-R-98 Delirium Rating Scale-Revised-98 | 16 (13 severity) | 0–39 | Broad symptom coverage; research | Details |
| CAM-S CAM-Severity | 4 (short) / 10 (long) | 0–7 / 0–19 | Services already using the CAM | Details |
The directory holds further severity measures — DEL-S, CAM-ICU-7 (ICU), the Delirium-O-Meter, the Delirium Index, the original DRS, and the Communication Capacity & Agitation Distress scales. See all severity instruments →
The delirium severity crosswalk
Because different studies use different severity instruments, scores are not directly comparable — an MDAS of 12 is not a DRS-R-98 of 12. The NIDUS Measurement & Harmonization Core published a crosswalk providing expected mappings between the MDAS, DRS-R-98 and CAM-S, derived from co-administration data using item-response-theory methods.
Research use, not individual clinical conversion
The crosswalk supports comparison and combination of research studies. It is not validated for converting an individual patient’s score to guide treatment or other clinical decisions.
Rather than reproduce those equating tables here — where a transcription error could give a wrong clinical number — this directory links directly to the authoritative, maintained tool:
Use the validated crosswalk
The interactive severity crosswalk is maintained by NIDUS. Open the NIDUS delirium severity crosswalk →
If that address has moved, start at the NIDUS measurement resources. The crosswalk is the work of Gross, Jones, Marcantonio, Inouye and colleagues.
Choosing a severity measure
- Match the instrument to the setting. If your service already runs the CAM, the CAM-S adds severity with minimal extra burden; in the ICU, CAM-ICU-7 fits the existing CAM-ICU workflow.
- For trials and longitudinal research, the DRS-R-98 and MDAS have the deepest track records and the most cross-study comparability via the crosswalk.
- Measure the same thing each time. Severity trajectories are only interpretable if the instrument and rater training are held constant.
- Consider the patient's and family's experience alongside observed severity — the Delirium Burden (DEL-B) instruments capture distress that observer scales miss.