Assessing Disease Severity in AD, Psoriasis Through Transepidermal Water Loss, Temperature

Measuring temperature and the evaporation of water from the skin’s surface can serve as objective measures to help determine the severity of atopic dermatitis (AD) and psoriasis as well as identify which patients need intensive treatment, according to recent research.

The skin plays an important role in patient health by undergoing a continuous renewal process called homeostasis and through its barrier function, which protects against water loss and numerous external stressors. Psoriasis and AD are inflammatory skin diseases that occur when environmental and genetic factors interact and may alter the barrier function.

The authors of a study published in the Journal of Clinical Medicine sought to assess the effectiveness of temperature and transepidermal water loss (TEWL) to see if they could serve as objective measures of the severity of cases of psoriasis and AD and pinpoint which patients require intensive treatment.

There are multiple diagnostics tools to evaluate severity of the 2 skin conditions. The psoriasis area severity index (PASI) is the most widely used for psoriasis and quantifies the percentage of the skin affected in 4 different anatomical regions and the intensity of psoriatic plaques. For AD, the SCORing Atopic Dermatitis (SCORAD) relies on the extent of the disorder, the intensity of symptoms such as redness and the effects of scratching, and subjective symptoms such as itch and sleeplessness, the study notes.

However, because the tools involve subjectivity, a significant amount of variability results, the authors said. With reports about barrier function characteristics scarce, they sought to evaluate skin homeostasis and epidermal barrier function of both lesioned and nonlesioned skins to further understand these diseases.

In this study, participants were recruited from the Dermatology Service of the Hospital Universitario Virgen de las Nieves in Granada from October 2019 to February 2020; the 314 participants consisted of 157 healthy individuals, 92 patients with psoriasis, and 65 with AD.

The variables were measured at 2 body sites in patients with psoriasis (a psoriatic plaque and an uninvolved skin area at the elbow); 2 body sites in patients with AD patients (a lesion with eczema and an uninvolved skin area at the volar forearm); and at the elbow in controls for psoriasis and the volar forearm for controls in AD.

The researchers found that temperature and TEWL values could help clinicians determine disease severity as well as identify which patients need more intensive treatment.

For patients with psoriasis, they found the following:

• Stratum corneum hydration (SCH) was lower at psoriatic plaques than uninvolved psoriatic skin and that of healthy control subjects.
• Psoriatic plaques had higher TEWL, temperature, and erythema (skin redness) values than uninvolved psoriatic skin.

For patients with AD, they found:

• TEWL was higher at lesions showing eczema than uninvolved skin and that of healthy control subjects.
• Patients with AD and more severe disease had a higher temperature, higher TEWL, and lower SCH at their lesions.

Two limitations of the study were the lack of follow-up and that patient groups included those using different treatments, which might alter the barrier function of the skin. But the results of the study show that the entire skin barrier is involved in both diseases, the authors said, and not just at the areas of plaques and lesions.

Reference

Montero-Vilchez T, Segura-Fernández-Nogueras M-V, Pérez-Rodríguez I, et al. Skin barrier function in psoriasis and atopic dermatitis: Transepidermal water loss and temperature as useful tools to assess disease severity. J. Clin. Med. Published online January 19, 2021. doi:10.3390/jcm10020359