How to Determine Acne Severity
Use the Investigator Global Assessment (IGA) 5-point scale (0-4: clear, almost clear, mild, moderate, severe) as your primary severity assessment tool, as it is the most commonly used system in the US with good clinician-patient agreement. 1
Recommended Grading Approach
The 2024 American Academy of Dermatology guidelines establish that while no universally accepted grading system exists, the IGA scale is preferred for clinical practice in the United States 1. This scale has been:
- Used extensively in randomized controlled trials
- Validated for good agreement between clinician and patient ratings
- Proposed as the framework for an ideal acne grading system
Components of an Ideal Assessment
When evaluating acne severity, systematically assess:
- Types of primary lesions present: comedones (open/closed), papules, pustules, nodules
- Number of lesions: quantify inflammatory and non-inflammatory lesions
- Extent and region of involvement: face, chest, back
- Secondary changes: dyspigmentation, scarring, erythema, pain 1
The 5-Point IGA Scale
Grade acne using this ordinal scale:
- 0 = Clear
- 1 = Almost clear
- 2 = Mild
- 3 = Moderate
- 4 = Severe
Note that specific descriptors for this scale are still being standardized and validated for facial and truncal acne 1.
Alternative Grading Systems
Other validated systems include 1:
- Leeds revised acne grading system
- Global Acne Grading System (GAGS)
- Global Acne Severity Scale
- Comprehensive Acne Severity Scale
These systems show strong correlations with IGA but are less commonly used in US clinical practice 2.
Critical Severity Considerations for Treatment Planning
Patients should be considered to have "severe" acne requiring isotretinoin if they have ANY of the following 1:
- Objectively severe acne on grading scale
- Psychosocial burden (depression, anxiety, social impairment)
- Active scarring or high risk of scarring
- Failed standard oral or topical therapy
This is crucial because traditional severity scales may underestimate disease impact—a patient with "moderate" acne by lesion count but significant psychological distress should be managed as severe disease.
Adjunctive Assessment Tools
Beyond objective grading, evaluate 1:
- Patient satisfaction with appearance
- Extent of scars and dark marks
- Treatment satisfaction
- Long-term acne control
- Impact on quality of life (use validated tools like DLQI)
Research shows that self-perceived severity often correlates more strongly with quality of life impairment than objective grading 3, highlighting the importance of incorporating patient perspective.
Photographic Documentation
Consider using digital photography for 1:
- Baseline documentation
- Monitoring treatment response
- Standardizing assessments over time
- Reducing inter-observer variability
Advanced modalities (fluorescent photography, polarized light, multispectral imaging) are increasingly used in clinical trials but remain optional in routine practice 1, 4.
Common Pitfalls to Avoid
- Don't rely solely on lesion counts: A patient with fewer lesions but nodules and scarring has more severe disease than one with many comedones
- Don't dismiss patient perception: Discordance between clinician and patient severity assessment predicts poor treatment adherence 3
- Don't overlook truncal involvement: Most grading systems focus on facial acne; remember to assess chest and back 5
- Don't delay escalation: Reassess at 3 months—if inadequate response (less than ~50% reduction in inflammatory lesions), escalate therapy to prevent scarring 6