What is the correlation between the Psoriasis Area Severity Index (PASI) and the Dermatology Life Quality Index (DLQI) in patients with plaque psoriasis?

From the Guidelines

The correlation between Psoriasis Area Severity Index (PASI) and Dermatology Life Quality Index (DLQI) in patients with plaque psoriasis is generally positive but moderate, as indicated by the British Association of Dermatologists guidelines for use of biological interventions in psoriasis 2005 1. This means that as the clinical severity of psoriasis (measured by PASI) increases, patients typically experience a greater negative impact on their quality of life (measured by DLQI).

• The PASI score is a validated measure of disease severity in chronic plaque psoriasis, with a score of > 10 (range 0–72) correlating with severe disease indicators such as need for hospital admission or use of systemic therapy 1.
• The DLQI is a validated tool for measuring quality of life across all skin diseases, with a score of > 10 (range 0–30) indicating at least a very large effect on an individual’s quality of life 1. However, this correlation is not perfect, as some patients with relatively mild clinical disease may experience significant quality of life impairment, while others with more severe clinical presentation might report less impact on their daily functioning.
• The relationship between these two measures highlights the importance of considering both objective clinical assessment and patient-reported outcomes when managing psoriasis, as emphasized in the guidelines 1. Clinicians should target both improvement in skin lesions and quality of life when determining treatment success, aiming for PASI 75 and DLQI ≤5 to ensure comprehensive care that addresses both the physical manifestations of psoriasis and its psychological and social consequences 1.

From the Research

Correlation Between PASI and DLQI

• The correlation between the Psoriasis Area Severity Index (PASI) and the Dermatology Life Quality Index (DLQI) in patients with plaque psoriasis has been studied in several research papers 2, 3, 4.
• A study published in 2021 found that PASI change was positively correlated with change in each assessed DLQI domain, with correlations ranging from weak to moderate over the initial treatment exposure period and moderate to strong over the sustained exposure period 2.
• In contrast, a study published in 2018 found that narrow-band UVB phototherapy reduced clinical severity of psoriasis, but did not improve quality of life as measured by DLQI, suggesting that clinical severity and quality of life impairment are independent of each other 3.
• Another study published in 2012 found that a PASI 90 response was necessary to achieve a DLQI of 0 or 1, and that patients who achieved a PASI 90 response had a significantly higher percentage of achieving a DLQI of 0 or 1 than those who achieved a PASI 75 but not a PASI 90 response 4.

Factors Influencing the Correlation

• The correlation between PASI and DLQI may be influenced by various factors, including the presence of comorbid psoriatic arthritis 2, treatment received 2, and stress related to psoriasis 5.
• A study published in 2015 found that stress, disease severity, and lower educational level were significant determining factors of a poorer quality of life in patients with psoriasis 5.

Measurement Tools

• The PASI and DLQI are commonly used tools to measure the severity of psoriasis and its impact on quality of life, respectively 2, 3, 6, 5, 4.
• Other tools, such as the Psoriasis Disability Index (PDI) and the Psoriasis Life Stress Inventory (PLSI), may also be used to assess the impact of psoriasis on quality of life and stress related to the condition 5.