Add the values for the intensity of Erythema, Induration and Desquamation
This is a free Psoriasis Area and Severity Index (PASI) Calculator for healthcare profesionals. Here you will find not only the free PASI calculator but also detailed information about how the PASI is calculated, its importance, its mathematic formula, and everything necessary to verify the resulting PASI score.
The Psoriasis Area and Severity Index (PASI) is a widely used tool for assessing the severity and extent of psoriasis. It combines the assessment of the severity of lesions and the area affected into a single score, ranging from 0 (no disease) to 72 (maximal disease). The PASI is a critical measure in both clinical practice and research to evaluate the effectiveness of treatments.
Psoriasis affects around 125 million people worldwide. Indeed, between 2% and 3% of the total population have psoriasis, according to the World Psoriasis Day consortium. Psoriasis is a chronic skin condition that significantly impacts patients' health and quality of life.
The PASI score helps clinicians determine the severity of their psoriasis and monitor treatment responses. It was created by Dr Torsten Fredriksson and Dr Ulf Pettersson in 1978 as an objective way to measure the effectiveness of psoriasis treatments.
This standardised scoring system allows for consistent assessment and comparison of disease severity, facilitating better patient management and enabling the evaluation of treatment efficacy in clinical trials.
The formula to calculate the PASI is the following:
PASI = 0.1 (Eh + lh + Sh) Ah + 0.2 (Eu + lu + Su) Au + 0.3 (Et + lt + St) At + 0.4 (El + ll + Sl) Al
Where:
On this page, you will find the PASI Calculator as well as the cutting-edge APASI, an automatic PASI calculator by Legit.Health that provides quick and accurate results from patient images to measure psoriasis severity.
The PASI score is calculated based on the severity of psoriasis lesions and the area of the body affected. To calculate the PASI score, one must follow these steps:
The body is divided into four regions: head, upper extremities, trunk, and lower extremities, each with a different weight factor.
This weight is calculated according to the standard of Body Surface Area, also known as BSA.
The clinical signs that must be assessed are:
Each of these signs is scored on a scale from 0 to 4, where:
With this in mind, you must assess the severity of each clinical sign for each of the four body regions. For example, a patient could have the following severity:
The affected area is measured in terms of the percentage that is affected, classified across six ranges:
For example, a patient could have the following severity:
Multiply the area score by the sum of the severity scores for erythema, induration, and desquamation. Then, multiply this result by the weight of the respective region. The final PASI score will range from 0 to 72.
For a patient with the following scores:
The PASI score would be calculated as follows:
As a result, the total PASI score would be 2.1 + 2 + 12 + 4.8 = 20.9
Although the Psoriasis Area and Severity Index (PASI) remains the most widely used tool for assessing psoriasis severity, it has several well-documented limitations. Researchers have highlighted various concerns over the years:
Several limitations of the PASI have been identified. Chief among them are:
Automated tools using Artificial Intelligence (AI) have been developed to reduce the effort and enhance the accuracy of the PASI scoring process. These tools analyse photographs of the affected skin areas, automatically identifying and quantifying clinical signs to calculate the PASI score.
In 2019, a multidisciplinary team of scientists from several countries developed the Automatic Psoriasis Area and Severity Index, also called APASI. The APASI automatically measures how much psoriasis a patient suffers from by analysing a photo of the patient through the use of Artificial Intelligence. The APASI is the automatic version of the PASI. Through the use of Artificial Intelligence, the APASI automatically calculates the PASI score.
The main objective of APASI (or Automatic PASI) is to provide a tool to accurately and consistently measure the severity of psoriasis during routine evaluations and clinical studies. The main advantage of the APASI is speed. The APASI requires only 23 seconds, while the manual PASI requires between six and 10 minutes.
Another advantage of APASI is the reduction in inter-observer variability. The APASI outperforms traditional methods, achieving a margin of error below 13%, much lower than the usual 20% observed in traditional manual PASI.
The APASI system represents the future of dermatology. It allows clinicians to benefit from the best tool for diagnosing and measuring the severity of psoriasis.
In essence, the APASI allows health care providers to practise evidence-based medicine and improves communication between doctor and patient.
This program is free software: you can redistribute it and modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your discretion) any later version.
This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, you can find it at https://www.gnu.org/licenses.
You can also find online free calculators for other dermatological scales and scoring systems:
Using Artificial Intelligence, APASI processes smartphone images and automatically translates them into the domain of the PASI.