Factors that predict disease severity in atopic dermatitis: The role of serum basal tryptase

BACKGROUND: Increased numbers of mast cells that contain tryptase are found in lesional atopic dermatitis (AD) skin. The association of serum basal tryptase (sBT) with anaphylactic reactions and mast cell diseases has recently been shown in children with venom and food allergy. OBJECTIVE: We aimed to identify the risk factors that predict the severity of AD and the association of sBT levels with AD and disease severity. METHOD: AD diagnosis was made according to Hanifin and Rajka criteria. Disease severity was scored by the objective scoring atopic dermatitis (SCORAD) index. The sBT levels were measured. Skin-prick testing, total immunoglobulin E, eosinophil percentages and counts, and a questionnaire concerning the history of atopic diseases and the risk factors of AD were applied. RESULTS: The children, ages 0.5 to 3.0 years, with AD (n = 85) were analyzed in two groups according to the presence (AD+/atopy+ [n = 55]) or absence (AD+/atopy- [n = 30]) of skin-prick test positivity. The comparisons were made with an age- and sex-matched control group (n = 82). The median (interquartile range) sBT in the AD+/atopy+, AD+/atopy-, and control groups were 5.01 ng/mL (2.75-6.79 ng/mL), 3.02 ng/mL (1.67-4.44 ng/mL), and 2.63 ng/mL (1.31-4.49 ng/mL), respectively (p = 0.003). The median (interquartile range) sBT levels were higher in patients with moderate-severe objective SCORAD index scores compared with the those with mild disease (3.85 ng/mL [2.04-5.91 ng/mL] versus 2.80 ng/mL [1.83-3.48 ng/mL]; p = 0.038). Multivariate logistic regression analysis showed that an sBT level of ≥3.9 ng/mL (odds ratio 8.77 [95% confidence interval, 1.87-41.18]; p = 0.006) was independently associated with an increased risk of moderate-severe AD (objective SCORAD index). CONCLUSION: To our knowledge, this was the first study that indicated that sBT levels may be important in the AD disease process and associated with the disease severity and atopy.