What is the Confusion Assessment Method (CAM)?

What is the Confusion Assessment Method (CAM)?

The Confusion Assessment Method (CAM) is a validated diagnostic instrument that enables trained healthcare professionals to rapidly identify delirium in less than 5 minutes using a four-feature algorithm based on DSM criteria. 1

Core Diagnostic Algorithm

The CAM diagnostic algorithm requires the presence of all of the following:

• Feature 1: Acute onset and fluctuating course - Must be present 1
• Feature 2: Inattention - Must be present 1
• Either Feature 3 OR Feature 4:
  • Feature 3: Disorganized thinking 1
  • Feature 4: Altered level of consciousness 1

A positive CAM diagnosis requires features 1 AND 2 AND either 3 OR 4. 1

Diagnostic Performance

The CAM demonstrates strong psychometric properties across multiple validation studies:

• Sensitivity: 82-100% (pooled meta-analysis: 82%, 95% CI: 69-91%) 1, 2
• Specificity: 89-99% (pooled meta-analysis: 99%, 95% CI: 87-100%) 1, 2
• High inter-rater reliability (kappa = 0.81-1.0) 2

Clinical Implementation

The CAM should be administered by trained healthcare staff as part of a comprehensive assessment that includes:

• Brief cognitive testing such as the Short Orientation Memory Concentration Test 1
• Attention testing (e.g., reciting months of the year backwards) 1
• Information from a knowledgeable informant about baseline cognitive function and acute changes 1

Available Variants

Multiple CAM adaptations exist for specific clinical settings:

• CAM-ICU: Designed specifically for intensive care unit patients with very good psychometric properties 1, 3
• B-CAM: Brief CAM variant for rapid screening 1
• Short CAM: Abbreviated version with available training manual 1
• Long CAM: Comprehensive version with detailed assessment 1

Recommended Assessment Frequency

Delirium screening should occur at least once per nursing shift (every 8-12 hours) given the fluctuating nature of delirium symptoms. 1, 3

Critical Clinical Pitfalls

Hypoactive delirium is frequently missed by clinical teams despite being the most common subtype, particularly in cancer patients and older adults. 3 This subtype presents with cognitive and motor slowing rather than agitation, making detection more difficult. 1

The CAM performs optimally when:

• Scored based on observations made during formal cognitive testing 4
• Administered by trained personnel who have completed standardized training 4, 5
• Used for screening rather than as the sole diagnostic criterion, with positive results confirmed by formal DSM or ICD criteria 1

Limitations in Clinical Practice

While the CAM has moderate-to-high sensitivity (81-86%) and specificity (63-84%) when compared against formal DSM criteria, it functions better as a screening tool than as a definitive diagnostic instrument. 6 Positive CAM results should prompt confirmation using formal DSM-IV or DSM-5 criteria for delirium. 1, 6