The relationship between serum transglutaminase-2 levels and the severity of chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is an immunological disease that is depicted by high prevalence and eminent burden for patients and society that is attributable to the arbitrary nature of symptoms and inconsistent tools for assessment of activity and severity. Transglutaminase-2 (TG2) is a posttranslational enzyme that is pervasively expressed in many cells and tissue types including mast cells. It has various biological functions, and its role in allergic disorders has been highlighted and delineated through several postulated mechanisms. This case-control study aimed at determining the relationship between serum levels TG2 and severity of CSU. To the best of our knowledge, this is the first study in Egypt to determine the relationship between serum TG2 and severity of CSU. We enrolled 60 adult patients with confirmed diagnosis of CSU. According to urticaria activity score (UAS), patients were categorized into three groups [20 with mild disease; UAS = 0, 20 with moderate disease; UAS = 1-3, 20 with severe disease; UAS = 4-6]. Another 20 healthy individuals (age and gender matched) served as a control group. All patients were subjected to detailed medical history, clinical examination, complete blood count with differential, serum total IgE, CRP, ESR, TSH, ANA, liver and renal function tests. Serum level of TG2 was done by quantitative ELISA for all enrolled patients and controls. Serum TG2 is significantly higher in patients group compared to control group (P value < 0.001). Serum TG2 levels were significantly higher in patients with severe disease compared to patients with moderate or mild disease. This is illustrated by the significant positive correlation between serum TG2 and UAS (r 0.814 and P value 0.000). Moreover, serum TG2 accurately classified CSU patients into mild, moderate and severe subgroups: as regards differentiation between mild and moderate cases (sensitivity 70%, specificity 80%, PPV 77.8, NPV 72.7) and as for the differentiation between moderate and severe cases (sensitivity 95%, specificity 90%, PPV 90.5, NPV 94.7). Serum TG2 may have a pivotal role as a marker of severity in patients with CSU.