TOPLINE:

In a study of infants younger than 2 years, serum thymus and activation-regulated chemokine (TARC) and squamous cell carcinoma antigen 2 (SCCA2) showed greater diagnostic accuracy for atopic dermatitis (AD) severity than total immunoglobulin E (IgE) and eosinophil counts.

METHODOLOGY:

• Researchers conducted a retrospective observational study of 50 children younger than 2 years (68% male; median age, 10 months) with newly diagnosed AD at Jikei University Katsushika Medical Center between March 2023 and November 2024.
• Primary caregivers completed the Patient-Oriented Eczema Measure (POEM) questionnaires at the initial visit; participants were subsequently categorized as having mild or moderate-to-severe disease on the basis of POEM scores.
• Blood samples were collected and analyzed for serum TARC, SCCA2, total IgE, and peripheral eosinophil counts.
• The primary endpoint was diagnostic performance (sensitivity, specificity, and area under the receiver operating characteristic curve [AUC]) of each biomarker; AUC ≥ 0.7 was considered acceptable diagnostic accuracy.
• Researchers used Spearman rank correlations to assess associations between biomarkers with AUC ≥ 0.7 and each POEM item (itching, sleep disturbance, bleeding, weeping, cracking, flaking, and dryness); a Spearman rank correlation coefficient (rs) ≥ 0.4 was indicated for statistical significance.

TAKEAWAY:

• SCCA2 demonstrated the highest diagnostic accuracy for distinguishing mild-to-worse AD from remission or almost clear disease (AUC, 0.708; 95% CI, 0.563-0.852; sensitivity, 0.773; specificity, 0.607).
• TARC showed the best performance for identifying moderate-to-worse disease vs mild-to-better disease (AUC, 0.717; 95% CI, 0.565-0.868; sensitivity, 0.636; specificity, 0.765).
• TARC exhibited significant positive correlations with the following POEM questionnaire items: itching (Spearman rs, 0.44; P < .01), bleeding (rs, 0.542; P < .01), and flaking off (rs, 0.417; P < .01), meeting the prespecified threshold of rs > 0.4.
• Total IgE and peripheral eosinophil counts showed poor diagnostic performance with AUC values around 0.5 for both mild and moderate disease severity classifications.

IN PRACTICE:

“Children aged < 2 years with AD, serum TARC, and SCCA2 showed stronger correlations with disease severity than total IgE or peripheral eosinophil counts,” the authors of the study concluded, noting that TARC was significantly associated with the POEM items “bleeding” and “flaking off.” These findings, they added, “suggest that the relative utility of TARC and SCCA2 may vary by clinical manifestation in early-stage AD” and lay “the groundwork for larger validation studies in infants.”

SOURCE:

The study was led by Sumire Seki, Jikei University Katsushika Medical Center, Tokyo, Japan, and was published online on March 29, 2026, in Pediatric Dermatology.

LIMITATIONS:

Limitations included the cross-sectional retrospective design, a small severe disease cohort, and the university hospital referral setting, which may have introduced selection bias toward more severe AD cases.

DISCLOSURES:

The study did not receive any specific funding. One author declared receiving honoraria for lectures from Torii Pharmaceutical, Otsuka Pharmaceutical Co., Sanofi KK, Regeneron Pharmaceuticals, AbbVie GK, Pfizer, LEO Pharma A/S, Maruho Co., and Sysmex Corporation. The remaining authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.