Positive Basophil Tests Are Linked to High Disease Activity and Other Features of Autoimmune Chronic Spontaneous Urticaria: A Systematic Review

Endotypes, phenotypes, and biomarkers in chronic spontaneous urticaria: Evolving toward personalized medicine

Chronic spontaneous urticaria (CSU) is an inflammatory disorder that manifests with hives, angioedema, or both and lasts more than or equal to 6 weeks. Although certain elements of CSU pathogenesis are well defined, others remain unclear. We discuss our current understanding of the underlying CSU endotypes, distinct clinical phenotypes, and predictive biomarkers. It is increasingly recognized that CSU comprises a spectrum of different underlying pathogenic mechanisms and distinct clinical presentations. Broadly, 2 endotypes that drive CSU pathogenesis have been identified, namely type I (autoallergic) and type IIb (autoimmune). However, a subpopulation shows evidence of both types, and some patients show evidence of neither. Multiple identified biomarkers have been associated with these endotypes or with disease features, such as CSU severity and duration. There is a lack of connectivity among the identified biomarkers, genetic risk loci, phenotypes, and corresponding endotypes, and each of these is frequently considered independently of the others. These identifiable features also have been associated with response, or lack thereof, to available therapies. Future investigations should optimize the endotyping of CSU using point-of-care, noninvasive, accessible biomarkers and assess the differences in response to therapy. With multiple treatments in late-stage development, establishing clearly defined CSU endotypes will facilitate future treatment decision-making and tailored treatment approaches and will inform optimal trial design.

Relevance of the basophil activation test in a cohort of 240 patients with chronic spontaneous urticaria

BACKGROUND

The basophil activation test (BAT) is considered to be the best biomarker to predict autoimmune chronic spontaneous urticaria (aiCSU). To date, few studies have investigated the utility of BAT in real-world clinical practice, the role of aiCSU biomarkers in relation to omalizumab therapy and the degree of association between different aiCSU tests.

OBJECTIVES

To analyse the clinical and laboratory features of a prospective cohort with chronic spontaneous urticaria (CSU) according to their BAT status, as well as to study omalizumab efficacy according to aiCSU biomarkers.

METHODS

A prospective study was conducted from 2010 to 2024 in patients with CSU. BAT alongside other laboratory tests were performed, and clinical and therapeutic features were prospectively collected. Data obtained were compared according to BAT status (positive vs. negative). Furthermore, omalizumab drug survival was typified according to aiCSU biomarkers.

RESULTS

In total, 240 patients were included in the study. Patients who were BAT positive presented more frequently with low IgE levels, higher occurrence of IgG antithyroid peroxidase (anti-TPO) positivity, autologous serum skin test (ASST) positivity, basopenia and eosinopenia. Multivariate logistic regression revealed that ASST [odds ratio (OR) 7.69, 95% confidence interval (CI) 2.81-21.0] and anti-TPO (OR 2.63, 95% CI 1.05-6.61) were associated with BAT positivity. All aiCSU biomarkers (BAT, ASST, combined ASST/BAT positivity and low IgE/anti-TPO+) were associated with significantly shorter omalizumab survival because of treatment failure. In the cohort, both low IgE/anti-TPO+ and ASST were associated with BAT positivity.

CONCLUSIONS

The use of BAT in clinical practice delineates a subgroup of patients with specific clinical, laboratory and therapeutic features, including increased omalizumab failure.

Utility of serum biomarkers in real-world practice for predicting response to omalizumab therapy in patients with chronic spontaneous urticaria

Background

Omalizumab (OMA), a recombinant humanized IgG monoclonal anti-IgE antibody, is approved for treatment for chronic spontaneous urticaria (CSU) refractory to second-generation H1-antihistamine (SGAH) therapy. However, currently, there are no validated serum biomarkers to reliably predict response to OMA treatment.

Objective

We explored the real-world clinical utility of using serum biomarkers for predicting response to OMA for CSU patients with disease refractory to high-dose SGAH therapy.

Methods

A single-center, retrospective chart review of CSU patients treated with OMA enrolled patients who had at their initial evaluation collection of a basophil histamine release assay for detecting IgG antibodies targeting FcεR1α subunit before starting OMA treatment. In addition, total IgE, IgG-anti-thyroid peroxidase (TPO), C-reactive protein, and absolute eosinophil count, if available, were analyzed as predictors for OMA response. The validated Outcome and Assessment Information Set Database (OASIS-D) rating system was used to assess responsiveness to OMA.

Results

High levels of IgG-anti-TPO were significantly associated with a poor response to OMA. However, basophil histamine release assay, total IgE, C-reactive protein, and absolute eosinophil count, as well as IgG-anti-TPO/total IgE ratios, were not predictive of a response to OMA therapy.

Conclusions

This real-world study confirms previous reports that a high IgG-anti-TPO level is a reliable predictor of poor response to OMA. However, better validation of basophil histamine release assay and other immunoassays that measure IgG antibodies to FcεR1α subunit are required before they can be recommended as predictors for OMA response. Whether any of these biomarkers are relevant for predicting response to novel advanced therapeutics under current development requires further investigation.

Flow cytometry-based basophil and mast cell activation tests in allergology: State of the art

The major challenge in allergy diagnosis is development of accessible and reliable diagnostics that can predict the clinical outcome following exposure to culprit allergen(s) or cross-reactive molecules and identification of safer alternatives than the current state-of-the-art methods. There is accumulating evidence that flow-based analyses for the quantification of activated basophils and mast cells subsequent to in vitro challenge (the basophil and mast cell activation test [BAT/MAT] or basophil activation test [BAT] and mast cell activation test [MAT]) could meet the diagnostic requirements for IgE-dependent allergies, drug hypersensitivities, and subsets of autoimmune urticaria. Furthermore, the BAT and MAT have found application in research and other nondiagnostic fields. However, appropriate use of the BAT and MAT requires understanding of the diversity of the source materials used and degranulation metrics to ensure correct test performance and interpretation of results. In this review, we provide the main applications and limitations of the BAT and MAT, as performed thus far.

Chronic Spontaneous Urticaria: An Update on the Evaluation and Management

Chronic spontaneous urticaria (CSU) affects 0.5% to 1% of the general population and is often managed by allergy and immunology specialists. Guidelines have evolved over the past several decades with an emphasis on decreasing extensive screening laboratory testing as they are of low-yield and cost-ineffective. The utility of biomarkers remains under investigation but total immunoglobulin E may be helpful in determining specific endotypes and response to omalizumab. Antihistamines and omalizumab remain the primary therapeutic options for CSU, but an expanding body of evidence supports the use of immunosuppressants and anti-inflammatory medications in refractory cases.

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.

Chronic spontaneous urticaria: Evidence of systemic microcirculatory changes

BACKGROUND

Chronic spontaneous urticaria (CSU) is a chronic inflammatory skin disease where activation of endothelial cells (ECs) at sites of skin lesions leads to increased blood flow, leakage of fluid into the skin, cellular infiltration, and vascular remodeling. To understand the disease duration and the sometimes vague systemic symptoms accompanying flares, the objective of this study was to examine if CSU comes with systemic vascular changes at the microcirculatory level.

METHODS

We investigated CSU patients (n = 49) and healthy controls (HCs, n = 44) for microcirculatory differences by nailfold videocapillaroscopy (NVC) and for blood levels of the soluble EC biomarkers serum vascular endothelial growth factor (VEGF), soluble E-selectin, and stem cell factor (SCF). Patients were also assessed for clinical characteristics, disease activity, and markers of autoimmune CSU (aiCSU).

RESULTS

CSU patients had significantly lower capillary density, more capillary malformations, and more irregular capillary dilations than HCs on NVC. Serum levels of VEGF, soluble E selectin and SCF were similar in CSU patients and HCs. CSU patients with higher VEGF levels had significantly more abnormal capillaries. Patients with markers of aiCSU, that is, low IgE levels or increased anti-TPO levels, had significantly more capillaries and less capillary dilations than those without.

CONCLUSION

Our results suggest that CSU comes with systemic microcirculatory changes, which may be driven, in part, by VEGF.