Atopic Dermatitis' Longitudinal Course Often Gets Overlooked

In the opinion of Raj Chovatiya, MD, PhD, the longitudinal course of atopic dermatitis (AD) is an important yet overlooked clinical domain of the disease.

Dr Raj Chovatiya

"We know that AD is associated with fluctuating severity, disease flares, long-term persistence, and periods of quiescence, but its longitudinal course is not routinely incorporated into guidelines or clinical trials," Chovatiya, assistant professor in the department of dermatology at Northwestern University, Chicago, said during the Revolutionizing Atopic Dermatitis virtual symposium. "Understanding the long-term course may improve our ability to phenotype, prognosticate, and personalize our care."

The classic view of AD is that it starts in early childhood, follows a waxing and waning course for a few years, and burns out by adulthood. "I think we all know that this is generally false," he said. "This was largely based on anecdotal clinical experience and large cross-sectional studies, not ones that consider the heterogeneity of AD."

Results from a large-scale, prospective study of 7,157 children enrolled in the Pediatric Eczema Elective Registry (PEER), suggests that AD commonly persists beyond adulthood. PEER was a phase IV postmarketing safety study of children aged 12-17 with moderate to severe AD who were exposed to topical pimecrolimus and who were surveyed every 6 months (JAMA Dermatol. 2014;150[6]:593-600). The researchers found that more persistent disease was associated with self-reported disease activity, many environmental exposures, White race, history of AD, and an annual household income of less than $50,000. By age 20, 50% reported at least one 6-month symptom- and medication-free period. "The important takeaway was that at every age, greater than 80% reported active AD as defined by symptoms or medication use, meaning that persistence was extremely high – much higher than what was originally thought," Chovatiya said. "If you take a look at the literature before this study, many were retrospective analyses, and persistence was estimated to be in the 40%-60% range."

International prospective studies have provided a more conservative estimate of persistence. For example, the German Multicenter Allergy Study followed 1,314 from birth through age 7 (J Allergy Clin Immunol. 2004;113[5]:925-31). Of these, 22% had AD within the first 2 years of life. Of these, 43% were in remission by age 3, while 38% had intermittent AD, and 19% had symptoms every year of the study. "Studies of other birth cohorts in the world came out suggesting that the rates of AD persistence ranges in the single digits to the teens," Chovatiya said.

To reconcile these heterogeneous estimates of AD persistence, researchers conducted a systematic review and meta-analysis of 45 studies that included 110,651 subjects from 15 countries and spanned 434,992 patient-years (J Am Acad Dermatol. 2016;75:681-7.e11). They found that 80% of childhood AD had at least one observed period of disease clearance by 8 years of age. "Most importantly, less than 5% of childhood AD was persistent 20 years after diagnosis," Chovatiya said. "However, interestingly, increased persistence was associated with later onset AD, more years of persistence, and more patient/caregiver-assessed disease." He pointed out inherent limitations to all studies of AD persistence, including nonuniform methods of data collection, differing cohorts, different ways of diagnosing AD, different disease severity scales, and the fact that most don't assess flares or recurrence beyond the initial period of disease clearance. "This can lead to a potential underestimation of longer-term persistence," he said.

Childhood AD features unique predictors of persistence that may define AD trajectories. For example, in several existing studies, more persistent disease was associated with higher baseline severity, earlier-onset AD, personal history of atopy, family history of AD, AD genetic risk score (heritability, including common Filaggrin mutations), urban environment, non-White race, Hispanic ethnicity, female sex, lower household income, and overall poorer health status.

"When it comes to evaluating the longitudinal course of AD in clinical practice, consideration of fluctuation, persistence, and improvement over time may actually improve our clinical decision-making and help set realistic expectations for our patients," Chovatiya said. "I think that AD classification can take a lesson from asthma. When we think about how our allergy colleagues think about asthma, it is commonly classified as intermittent, mild persistent, moderate persistent, and severe persistent. Those that have intermittent disease get reactive treatment, while those with persistent disease get proactive treatment. Similarly, AD could be classified as mild intermittent, mild persistent, moderate to severe intermittent and moderate to severe persistent."

He concluded his presentation by recommending that the fluctuating course of AD be better captured in clinical trials. "Current randomized, controlled trials use validated measures of AD signs and symptoms as inclusion criteria and measures of efficacy," he said. "Static assessments may confound treatment effects, and assessment of prespecified time points are somewhat arbitrary in the context of disease subsets." He proposes studies that examine aggregate measures of long-term disease control, such as number of itch-free days, weeks with clear skin, and flares experienced. "Long-term control assessment in RCTs should include signs, symptoms, health-related quality of life, and a patient global domain over time to better understand how AD is doing in the long run," he said.

Chovatiya disclosed that he is a consultant to, a speaker for, and/or a member of the advisory board for AbbVie, Arcutis, Arena, Incyte, Pfizer, Regeneron, and Sanofi Genzyme.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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