What are the recommended tests and assessments for diagnosing delirium?

Delirium Diagnosis: Clinical Assessment and Testing

Primary Diagnostic Approach

The diagnosis of delirium must be made by a trained healthcare professional using clinical assessment based on DSM-5 or ICD criteria, not by screening tools alone. 1 This represents the reference standard and requires expertise in evaluating fluctuating cognitive symptoms, inattention, altered consciousness, and disorganized thinking. 2

The Confusion Assessment Method (CAM) Algorithm

The CAM is the most widely validated diagnostic instrument and should guide your clinical assessment, requiring all of the following:

• Feature 1 (Required): Acute onset and fluctuating course of symptoms 1, 2, 3
• Feature 2 (Required): Inattention 1, 2, 3
• Feature 3 OR 4: Either disorganized thinking OR altered level of consciousness 1, 2, 3

The CAM demonstrates 82-100% sensitivity and 89-99% specificity across populations. 2, 3 In cancer patients specifically, sensitivity was 88% and specificity was 100%. 1

Bedside Cognitive Testing Components

During your clinical assessment, you must administer brief cognitive tests to objectively document inattention:

• Months of the year backwards (MOTYB) - tests attention directly 1, 2
• Short Orientation Memory Concentration Test (SOMCT) - provides structured cognitive assessment 1, 2
• Repeated assessments throughout the day - essential because cognitive status fluctuates substantially hour-to-hour 2, 4

Critical History-Taking Requirements

Obtain collateral history from family members or caregivers to establish:

• The patient's baseline cognitive function before symptom onset 1, 2, 4
• Exact timeline of cognitive changes 2
• Medication changes, including over-the-counter drugs 4
• Recent infections, falls, or medical events 4

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) short form can formalize this collateral information. 1

Laboratory and Imaging Workup

Laboratory testing should be clinically guided, not routine, but typically includes:

• Complete blood count and comprehensive metabolic panel 4
• Urinalysis and blood glucose 4
• Thyroid function tests 4

Neuroimaging (CT or MRI) is indicated only when specific features are present:

• Focal neurological deficits 4
• Recent head trauma 4
• New-onset seizures 4
• Signs of increased intracranial pressure 4
• Unexplained altered mental status despite initial workup 4

Additional testing includes ECG for arrhythmias/ischemia and chest X-ray for pneumonia when clinically indicated. 4

Position on Screening Tools

The evidence is insufficient to recommend routine use of screening tools for diagnosis in cancer patients, though they may aid trained clinicians. 1 While the CAM has strong psychometric properties, screening tools risk misclassification—either falsely treating non-delirious patients or missing true delirium. 1

However, given delirium's high morbidity and mortality, all hospitalized patients should be observed at least daily for sentinel changes: 1

• Impaired concentration or slow responses 1
• Withdrawal or sleep disturbances 1
• Hallucinations, confusion, or agitation 1
• Restlessness or mood changes 1

Special Populations and Pitfalls

Hypoactive delirium is the most commonly missed subtype because patients appear quiet and withdrawn rather than agitated. 4 This presentation is particularly common in cancer patients and requires high clinical suspicion. 4

Delirium superimposed on dementia is especially challenging to diagnose but carries grave prognostic implications including accelerated cognitive decline, longer hospitalizations, and higher mortality. 2 The acute onset and fluctuating course distinguish delirium from the insidious, progressive course of dementia alone. 2

Do not perform formal cognitive testing until 2-4 weeks after complete delirium resolution, as assessments during active delirium are unreliable due to fluctuations. 2, 5

Assessment Frequency in High-Risk Settings

In ICU settings, assess for delirium every 8-12 hours (at least once per shift) using CAM-ICU or Intensive Care Delirium Screening Checklist (ICDSC). 4 High-risk patients include those with dementia, hypertension, alcoholism, severe illness, mechanical ventilation, or receiving sedatives/opioids. 4

Clinical Urgency

Delirium represents a medical emergency that, if untreated, can be fatal or cause irreversible cognitive and functional losses. 2, 5 Prompt identification through systematic clinical assessment using DSM/ICD criteria, augmented by CAM features and bedside cognitive testing, is essential for improving outcomes. 1