Between 80 percent and 90 percent of people with psoriasis have plaque psoriasis symptoms. Itchy, painful, and sometimes visible scaly patches can get in the way of normal activities. In fact, about 60 percent of people with psoriasis say their skin condition negatively affects their daily lives. How your plaque psoriasis affects your life is one factor that helps your doctor determine how severe your disease is.

There are several ways your dermatologist can determine whether your plaque psoriasis is mild, moderate, or severe. Sometimes doctors or researchers will use more than one method. By assessing the severity of your psoriasis, a doctor can track how effective your treatments are and justify their necessity to insurance companies. In research studies, assessing severity helps researchers understand if a treatment is effective.

Here are six ways to determine the severity of plaque psoriasis, along with insights from MyPsoriasisTeam members living with the condition.

1. Physician Global Assessment

The Physician Global Assessment (PGA) is a simple evaluation of psoriasis severity. Doctors rate the basic characteristics of plaques on a scale of zero to 4 or 5 and average the numbers for a final score. A score of 2 is considered mild and 4 is considered severe.

There are different PGA variations, but usually, the evaluation considers scaling, color intensity, and thickness of plaques.

The PGA doesn’t account for how much of the body is covered in psoriasis symptoms. The definitions of each score also vary between versions, so it’s not as useful a tool when comparing different research studies. For this reason, this assessment is not used as much in research.

2. The Psoriasis Area and Severity Index

The Psoriasis Area and Severity Index (PASI) is a calculation used to rate the severity of plaque psoriasis. First, the dermatologist identifies a psoriasis sample from four body regions: head and neck, upper limbs, trunk, and lower limbs. Then they rate three characteristics — erythema (intensity of color), desquamation (scaling), and induration (thickening and hardening of skin) — on a scale of zero through 4. “None” is a zero, followed by mild (1), moderate (2), severe (3), and very severe (4).

The PASI also considers how much of the body is covered with psoriasis symptoms, which is rated from zero to 6. Zero means no symptoms and 6 means 90 percent to 100 percent of the skin in a certain area is covered.

Your numbers are entered into a formula to get a score from zero to 72. More than 10 is considered severe, and 5 to 10 is moderate. Below 5 is mild or clear.

Clinical studies often determine the effectiveness of psoriasis treatments based on the change in PASI score. Many newer biologics reduce the PASI score significantly.

However, a PASI score doesn’t tell the whole story. Without taking into account quality-of-life considerations or the psychological impact of psoriasis, the PASI may sometimes underestimate how severely a person is affected by psoriasis.

3. Investigator Global Assessment

The Investigator Global Assessment (IGA) is similar to the PGA, but instead of being geared toward physicians, it’s meant for investigators conducting clinical trials.

Investigators use a zero to 4 scale to judge plaque severity and come up with an average score. A static IGA scale analyzes a single point in time, and a dynamic IGA scale includes baseline severity.

For instance, a score of 1 indicates mild discoloration without noticeable skin thickening, whereas a severe score of 4 describes a lot of thickening and major discoloration. Some critics of the IGA say it doesn’t capture the extent of psoriasis on the body. It also doesn’t account for additional symptoms, like psoriatic arthritis.

4. Dermatology Life Quality Index

The Dermatology Life Quality Index (DLQI) is a 10-question survey that measures how skin diseases affect quality of life. This test has been used to assess more than 60 skin conditions in more than 80 countries. It’s used in clinical trials and in doctors’ offices.

The questionnaire covers topics like:

• Pain and discomfort
• Self-consciousness
• Daily activities like shopping or taking care of your home
• Social and leisure activities
• Work and education
• Family and friendships
• Romantic relationships and sex

You’ll answer each question “very much,” “a lot,” “a little,” or “not at all.” The exact wording may vary depending on the version of the test you receive. “Very much” is 3 points and “not at all” is zero points. The maximum score is 30. After adding up the total for the 10 questions, providers estimate the overall impact of psoriasis symptoms on someone’s life.

5. International Psoriasis Council Consensus

The International Psoriasis Council (IPC) published an article in 2020 rethinking how to classify the severity of psoriasis. The IPC emphasized that severity definitions should focus on the individual and account for how psoriasis affects a person’s emotional well-being. The paper notes that some of the measurement tools mentioned above may not adequately capture how severe someone’s psoriasis is.

Rather than defining specific categories of severity, the IPC recommended that doctors evaluate individuals as candidates for either topical-only treatment (applied to the skin) or systemic therapies (affecting the entire body). According to the IPC, a person should be considered eligible for systemic therapy if they meet one of the criteria below:

• Body surface area is greater than 10 percent.
• Psoriasis symptoms appear on particular areas, such as the face, scalp, hands, feet, or genitals.
• Topical treatments haven’t been effective.

Several national and regional psoriasis treatment guidelines reflect aspects of the IPC recommendations.

6. Your Personal Experience

No test can replace your own experience of living with plaque psoriasis. Only you know how the condition affects your physical and mental health, as well as your ability to do your job, care for loved ones, and reach your goals.

It’s important to tell your doctor how plaque psoriasis is affecting all aspects of your life. You can be proactive in the process by taking photos, keeping a journal, and detailing your symptoms to share during appointments. By giving your dermatologist a more accurate look at your plaque psoriasis between visits, you’re more likely to receive the right level of care.

Treatment for Plaque Psoriasis

Your dermatology provider may recommend treatments such as phototherapy, topical therapy, oral medications, or injected biologics to treat plaque psoriasis. The right treatment will depend on factors like how severe your psoriasis is, if you have joint symptoms, and your treatment history. Identifying and avoiding triggers is also important for managing your symptoms.

MyPsoriasisTeam members have reported success treating severe psoriasis. One member shared, “I have plaque psoriasis and inverse psoriasis. It gets really bad on my scalp and behind my ears. I’ve tried multiple pills, creams, and injections. One biologic injection works great for me. It clears up my plaques, but I still have joint pain.”

Another member wrote, “Loving my biologic. It makes me forget I have severe plaque psoriasis!”

Talk With Others Who Understand

On MyPsoriasisTeam, people share their experiences with psoriasis, get advice, and find support from others who understand.

Is your psoriasis severe? Let others know in the comments below.