1. What is BSA in Psoriasis?

Body Surface Area (BSA) affected by psoriasis is a key measure of disease severity. It estimates the percentage of skin covered by psoriatic lesions, helping clinicians determine treatment approaches and monitor disease progression.

2. How to Use the Palm Method

The palm method is a simple clinical tool where:

Key Points:

• Use the patient's own palm (including fingers) as reference
• For larger contiguous areas, estimate how many palms would cover it
• Special areas (face, genitals) count as 1% each

3. Importance of BSA Measurement

Clinical Significance: BSA assessment helps classify psoriasis severity:

• Mild: <3% BSA
• Moderate: 3-10% BSA
• Severe: >10% BSA

This classification guides treatment decisions and helps evaluate treatment response over time.

4. Using the Calculator

Instructions:

1. Count the number of palm-sized areas affected (1 palm ≈ 1%)
2. For larger contiguous areas, select the appropriate option
3. The calculator sums these values to estimate total %BSA affected

5. Frequently Asked Questions (FAQ)

Q1: How accurate is the palm method?
A: While not as precise as digital imaging, it's clinically practical with good inter-rater reliability when performed consistently.

Q2: What about very small lesions?
A: Cluster small lesions together and estimate how many palms they would cover in total.

Q3: Does BSA alone determine severity?
A: No - disease impact, location (e.g., face/hands), and symptoms must also be considered in severity assessment.

Q4: How often should BSA be measured?
A: At each clinical visit to monitor treatment response, typically every 3-6 months for stable patients.

Q5: Are there alternative measurement methods?
A: Yes - the Rule of Nines (more precise but complex) and digital imaging tools (most accurate but not widely available).