Extended diagnostic value of autologous serum skin test and basophil CD63 expression assay in chronic urticaria

PD-BAT: A novel approach of pooling basophil donors for expansion of commercial laboratory testing of Chronic Spontaneous Urticaria

The type II autoimmune subtype of Chronic Spontaneous Urticaria (CSU) is characterized by the presence of IgG autoantibodies targeting IgE or the IgE high-affinity receptor (FcεRI) on mast cells and basophils. In evaluation of CSU patients, indirect basophil activation testing (BAT), has been utilized, involving the mixing of patient serum with heterologous peripheral blood donors, followed by flow cytometric assessment of basophil markers. However, the reliability of the indirect BAT results hinges on the quality of the donor basophils utilized. In this study, we introduce an innovative approach where multiple potential basophil donors undergo rigorous BAT characterization alongside control samples. By selecting and pooling donors with optimal performance, we significantly enhance the inter-assay reproducibility of the indirect BAT test.

Mast cell activation tests by flow cytometry: A new diagnostic asset?

Since the late nineties, evidence has accumulated that flow-assisted basophil activation test (BAT) might be an accessible and reliable method to explore the mechanisms governing basophil degranulation and diagnostic allowing correct prediction of the clinical outcome following exposure to the offending allergen(s) and cross-reactive structures for different IgE-dependent allergies and particular forms of autoimmune urticaria. Although the BAT offers many advantages over mediator release tests, it is left with some weaknesses that hinder a wider application. It is preferable to perform the BAT analysis within 4 h of collection, and the technique does not advance diagnosis in patients with non-responsive cells. Besides, the BAT is difficult to standardize mainly because of the difficulty to perform large batch analyses that might span over several days. This article reviews the status of flow cytometric mast cell activation test (MAT) using passively sensitized mast cells (MCs) with patients' sera or plasma (henceforth indicated as passive MAT; pMAT) using both MC lines and cultured MCs in the diagnosis of IgE-dependent allergies. In addition, this paper provides guidance for generating human MCs from peripheral blood CD34⁺ progenitor cells (PBCMCs) and correct interpretation of flow cytometric analyses of activated and/or degranulating cells. With the recent recognition of the mas-related G protein-coupled receptor X2 (MRGPRX2) occupation as a putative mechanism of immediate drug hypersensitivity reactions (IDHRs), we also speculate how direct activation of MCs (dMAT)-that is direct activation by MRGPRX2 agonists without prior passive sensitization-could advance paradigms for this novel endotype of IDHRs.

Successful Treatment of Autoimmune Urticaria with Low-Dose Prednisolone Therapy Administered for a Few Months: A Case Series of 42 Patients

BACKGROUND

Chronic spontaneous urticaria (CSU) is defined as symptoms of urticaria persisting for 6 weeks or more without obvious cause. Autologous serum skin test (ASST) positivity in patients with CSU is considered to be associated with autoimmune urticaria (AIU).

METHODS

In this retrospective study we retrieved the medical records of 1,073 urticaria patients seen at the Department of Dermatology and Allergology of Szeged University between January 2005 and February 2014. Forty-two patients (36 female and 6 male) met the study criteria by having CSU and giving positive results in the ASST. Our aim was to assess the clinical efficacy and safety of low-dose oral prednisolone therapy administered to patients with antihistamine-refractory ASST-positive CSU for a few months. Patients were given an initial dose (40 mg/day) of prednisolone until the complete resolution of the symptoms, usually 7-10 days, and then the dose was gradually decreased, as in other autoimmune diseases.

RESULTS

Prednisolone therapy lasted for an average of 3.6 months and a complete long-lasting response was achieved in 35 of 42 AIU patients (83.3%). The follow-up period was at least 36 months (3 years) for each AIU patient; the longest follow-up time was 139 months (11.5 years). None of the patients reported any considerable side effects.

CONCLUSION

Based on our results, we suggest that the use of this treatment could be an alternative for the treatment of AIU. Our present results also highlight the need for other therapies in a small percentage of AIU patients. Our results suggest that AIU represents a transient autoimmunity that can be successfully treated with low-dose steroid therapy administered for a few months.

Positive CD63 Basophil Activation Tests Are Common in Children with Chronic Spontaneous Urticaria and Linked to High Disease Activity

BACKGROUND

The basophil activation test (BAT) using CD63 expression is a sensitive and specific tool for the diagnostic workup of autoimmune chronic spontaneous urticaria (CSU). The definition of a positive BAT is directly dependent on the reference range and the cutoff values established in control populations. As of now, the pediatric reference range and cutoff values of the CD63 BAT remain to be established.

METHODS

In this study, we analyzed CD63 expression in 80 children (1-17 years old) without chronic urticaria (i.e., controls) and compared the values to those of a pediatric cohort of 105 CSU patients and 23 physical urticaria (PU) patients.

RESULTS

Based on the log-normal distribution of CD63 values in control subjects, the reference range and the cutoff for positive CD63 BAT values was established to be 1.2-1.8% (95% CI) and 1.8%, respectively. Children with CSU showed significantly elevated and significantly increased BAT values compared to healthy controls (Wilcoxon rank test p value <0.001). In contrast, no difference was found between BAT results in controls and PU patients. In pediatric CSU patients, a higher disease activity was associated with higher BAT values.

CONCLUSIONS

Our study provides, for the first time, reference and cutoff values for the CD63 BAT in children. Our findings show that positive CD63 BAT are common in children with CSU and linked to a high disease activity.

Basophil Activation Test identifies the patients with Chronic Spontaneous Urticaria suffering the most active disease

Introduction

The basophil activation test showing CD63 up regulation could be a specific and sensitive in vitro complementary text to the in vivo autologous serum skin test for the activity assessment of the patients suffering autoimmune chronic spontaneous urticaria. The aim of this study is to define the basophil activation test as a useful tool in clinical practice in order to identify those patients with more active disease.

Methods

We screened 139 patients (96 women) diagnosed of chronic spontaneous urticaria using simultaneously autologous serum skin test and basophil activation test and their relationship with disease activity.

Results

Positive autologous serum skin test was found in 56.8%; from them, 31.6% were basophil activation test positive. Negative autologous serum skin test result was found in the 43.2% of the sample that showed negative CD63 expression results in all cases, except one. Patients with positive autologous serum skin test and positive CD63 by basophil activation test showed significant higher Urticaria Activity Score of 7 days (P = 0.004) and of 3 weeks (P = 0.001) than patients with positive autologous serum skin test and negative CD63 (mean ± standard deviation [SD] 26.57 ± 10.56 versus 18.40 ± 12.05 for the Urticaria Activity Score of 7 days and 56.47 ± 23.78 versus 39.88 ± 25.44 for the Urticaria Activity Score of 3 weeks).

Conclusions

The CD63 expression on basophils appears as a reliable in vitro marker, useful in clinical practice in combination with autologous serum skin test to define chronic spontaneous urticaria patients with the highest urticaria activity that impairs a normal life.