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      Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm

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    Patent Pending

    Psoriasis Area and Severity Index (PASI)

    Quantifies severity of psoriasis.
    When to Use
    Pearls/Pitfalls
    Why Use
    • Patients with psoriasis.

    • Use with caution in patients with smaller areas of involvement, as the score is less sensitive in those cases.

    • Initially developed to assess treatment efficacy of retinoids.

    • PASI is the most widely used psoriasis clinical severity score.

    • Validated using palm method of body surface area estimation (patient’s palm, excluding fingers, roughly correlates to 1% BSA).

    • PASI is neither a linear nor normally distributed score, as it is less sensitive at lower end of scale, and accurate PASI assessment requires some level of clinical gestalt in assigning points.

    • PASI is limited by lack of interrater and intrarater reliability, and lack of utility in detecting change in mild psoriasis.

    • Calculating the PASI can be error-prone if not done systematically.

    • May be used to track disease progression and help guide treatment (e.g. retinoids).

    • In some countries (e.g. Australia), PASI is used to determine eligibility for government-subsidized prescription drugs.

    • Used in clinical trials of therapies to treat psoriasis.

    Head/neck
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    0%
    1-9%
    10-29%
    30-49%
    50-69%
    70-89%
    90-100%
    Upper limbs
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    0%
    1-9%
    10-29%
    30-49%
    50-69%
    70-89%
    90-100%
    Trunk
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    0%
    1-9%
    10-29%
    30-49%
    50-69%
    70-89%
    90-100%
    Lower limbs
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    None
    Slight
    Moderate
    Severe
    Very severe
    0%
    1-9%
    10-29%
    30-49%
    50-69%
    70-89%
    90-100%

    Result:

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    Next Steps
    Evidence
    Creator Insights
    Dr. Torsten Fredriksson

    About the Creator

    Torsten Fredriksson, MD, is a physician in the department of dermatology at the Karolinska Institute in Sweden. Dr. Fredriksson’s primary research is focused on topical treatments for conditions like psoriasis, dermatomycosis, and tinea versicolor.

    To view Dr. Torsten Fredriksson's publications, visit PubMed

    Are you Dr. Torsten Fredriksson? Send us a message to review your photo and bio, and find out how to submit Creator Insights!
    MDCalc loves calculator creators – researchers who, through intelligent and often complex methods, discover tools that describe scientific facts that can then be applied in practice. These are real scientific discoveries about the nature of the human body, which can be invaluable to physicians taking care of patients.
    Content Contributors
    • Zhi Mei Low, MBBS
    Reviewed By
    • Johannes S. Kern, MD, PhD
    About the Creator
    Dr. Torsten Fredriksson
    Are you Dr. Torsten Fredriksson?
    Content Contributors
    • Zhi Mei Low, MBBS
    Reviewed By
    • Johannes S. Kern, MD, PhD