Plaques are raised patches of inflamed skin associated with psoriasis that look and feel different than the surrounding skin. The majority of people with psoriasis (80 percent to 90 percent) have plaques to some degree. However, there’s no single method that measures whether plaque psoriasis is mild or severe. Instead, dermatologists use their professional judgment and experience to assign a rating that helps guide treatment.

A combination of standardized diagnostic tools, along with subjective evaluations, lets your provider know how to care for your plaque psoriasis. A good dermatologist — a doctor specializing in skin disorders — understands that psoriasis doesn’t just affect how your skin looks, but also how it feels and affects your life. By measuring these characteristics, the doctor can assess the effectiveness of treatments and justify their necessity to insurance companies.

MyPsoriasisTeam members frequently offer advice and support for managing plaque psoriasis in different situations, like at the barbershop. “Definitely inform the barber of your psoriasis,” one member wrote. “Tell them about any plaques/sores/tenderness. Go in with clean hair. If you just generally have a tender scalp (like me), let them know. … I get a liquid prescription from my dermatologist called mometasone (Elocon) and put it right on the scalp plaque (just on the plaque, not the whole scalp). It’s very effective.”

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

1. The Psoriasis Area and Severity Index

Psoriasis Area and Severity Index (PASI) is a calculation that dermatologists use to rate the severity of plaque psoriasis. First, the doctor identifies a psoriasis sample from four body regions, including the head, upper extremities, trunk, and lower extremities. Then, they rate three characteristics — erythema (intensity of color), desquamation (scaling), and induration (thickening and hardening of skin) — on a scale of 0 through 4. “None” is a 0, followed by mild (1), moderate (2), severe (3), and very severe (4).

PASI also considers the level of psoriasis involvement, which is rated from 0 to 6, with 0 being no involvement and 6 representing 90 percent to 100 percent involvement.

Finally, these numbers are entered into a formula to get a score from 0 to 72. More than 10 is considered severe, and 5 to 10 is moderate. Below 5 is mild or clear. In addition, regions of the body are weighted in the equation based on how much body surface area (BSA) they cover.

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, PASI doesn’t tell the whole story. Without taking into account quality-of-life considerations or the psychological impact of psoriasis, PASI may underestimate disease severity in some cases.

2. Physician Global Assessment

The Physician Global Assessment (PGA) is a simpler evaluation of psoriasis severity. Clinicians rate the basic characteristics of plaques on a scale of 0 to 4 and average the numbers for a final score.

There are different variations of PGAs, but usually, PGA takes into account the same characteristics as PASI — scaling, color intensity, and thickness.

The ultimate result can range from clear with possible residual discoloration (0) to severe (4). PGA is considered reliable, especially if the same physician measures changes over time. But similar to the PASI, PGA is vulnerable to a clinician’s somewhat subjective evaluation, and it may not be accurate if multiple practitioners assess the same person at different times.

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 the same rating scale from 0 to 4 to determine plaque severity and come up with an average score. A static IGA scale analyzes a single point in time, and a dynamic IGA scale instead includes baseline severity.

For instance, a score of 1 indicates mild discoloration without noticeable skin thickening. But a severe score of 4 describes a lot of thickening and intense 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

No assessment of disease severity would be complete without addressing quality of life. The Dermatology Life Quality Index (DLQI) is a 10-question survey that explores the impact of plaque psoriasis. It looks at six different categories:

• Daily activities
• Leisure
• Personal relationships
• Symptoms and feelings
• Treatment
• Work and school performance

Some versions of the DLQI include one question per category, and others have two. If there’s one question, the maximum score for each area ranges from 0 to 3. For two questions, the total score per each is up to 6.

A higher score indicates a more significant impairment in quality of life. After adding up the total for the 10 questions, providers estimate the overall impact of psoriasis symptoms on an individual’s daily life.

Although the DLQI isn’t a perfect tool, it can help paint a picture of psoriasis severity in ways that other tools don’t consider. You can also use the DLQI as a jumping-off point to have a deeper conversation with your dermatologist about your life with plaque psoriasis.

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 be centered on the individual and account for how the skin condition affects emotional well-being.

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 exceeds 10 percent.
• Psoriasis symptoms appear on particular areas, such as the face, scalp, hands, feet, or genitals.
• Topical treatments haven’t been effective.

6. Your Personal Experience

No test can replace your perception of living with plaque psoriasis. Only you know how the condition affects your physical and mental health and how it affects your ability to do your job, care for your loved ones, and reach your goals. Psoriatic arthritis also needs to be factored into how you feel, because if left untreated, it can lead to pain and disfiguring arthritis.

Finding a health care provider who sees assessment tools as a starting point is vital to quality care. You should also feel listened to, and they should consider your input when choosing treatment options.

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 (like corticosteroid cream), oral medications, or injected biologics to treat plaque psoriasis. Identifying and avoiding triggers is also essential to the management of psoriasis, as is reducing risk factors and monitoring for common comorbidities (co-existing health conditions) like cardiovascular disease.

One MyPsoriasisTeam member shared their experience by explaining, “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.”

Biologic therapies like this one can be highly effective for the long-term management of moderate to severe plaque psoriasis, but they’re not without side effects. For mild psoriasis, your physician will probably recommend other therapies first, reserving systemic treatment and biologics for people with more severe cases. For people with psoriasis on more than 5 percent of their BSA, treatments usually include pills or injections, along with creams or other topical treatments.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and their loved ones. On MyPsoriasisTeam, more than 125,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

What factors do you feel are most important when rating your plaque psoriasis? What pharmaceuticals, supplements, or other treatments have made the biggest difference in your management of psoriasis? Post your suggestions in the comments below, or start a conversation on your Activities page.