OBJECTIVES: Our objective was to evaluate the relationship between atopic dermatitis (AD) disease activity (DA), as measured by body surface area (BSA) and physician global assessment (PGA), and systemic therapy initiation (STI).

METHODS: AD patients from 5 specialty dermatology networks within the OMNY Health Dermatology Database were indexed at their first DA assessment with both BSA and PGA measurements. Patients with no recent history of traditional systemic, biologic, or ultraviolet therapy were included and followed from index DA assessment until STI or censoring. Cox regression with time-varying effects was employed to quantify the independent contributions of BSA, PGA, and their product on time to STI while controlling for patient characteristics.

RESULTS: A total of 15,191 patients were included (57% female, 38% ages ≥ 60 years, 20% non-white among known values). Index BSA and PGA exhibited skewed (mean: 12; median: 5) and normal (mean, median: 2) distributions, respectively. After controlling for patient characteristics, BSA exhibited a strong dose-response-style relationship with earlier STI with hazard ratio (HR) point estimates ranging from 1.8 (BSA: 2-15%) to 3.6 (BSA ≥ 40%). Similar results were obtained for PGA with HR point estimates of 2.2 and 3.4 for moderate and severe, respectively. When both BSA and PGA were included together in the same model, relationships remained but were attenuated. HRs (95% confidence intervals [CIs]) were 1.3 (1.1-1.6), 1.5 (1.2-1.9), and 1.7 (1.3-2.1) for BSA categories of 2-15%, 16-39%, and ≥ 40%, respectively, and were 1.8 (1.4-2.3) and 2.7 (2.1-3.4) for moderate and severe PGA categories, respectively. Using the BSA-PGA product, HRs (95% CIs) were 0.8 (0.6-1.1), 1.8 (1.3-2.4), and 2.2 (1.6-3.1) for 1-29, 30-129, and 130-400 categories, respectively.

CONCLUSIONS: Results suggest meaningful independent contributions of BSA and PGA on STI in AD patients. The BSA-PGA product shows promise as a single metric for DA in AD.