D3.422 - Evaluating Elevated Baseline Mast Cell Tryptase: Insights from an Adult Allergy Service

Serum tryptase is a key marker of mast cell degranulation and is essential in the evaluation of anaphylactic reactions and suspected mast cell disorders. Basal serum tryptase (BST) measurements are particularly useful in identifying conditions such as Hereditary Alpha Tryptasemia (HαT), clonal mast cell disorders and systemic mastocytosis.

This service evaluation project examines patients with elevated BST (> 11.4 µg/L), to assess diagnostic pathways, adherence to guidelines, and clinical outcomes.

 We retrospectively reviewed BST measurements from 2017 to 2024 for patients presenting with drug, food, venom allergy, chronic urticaria and anaphylaxis.

Patient demographics, including ethnicity, were recorded. Key metrics included median BST, proportion of patients with follow-up measurements, results of HαT genetic testing, haematology referrals, and bone marrow biopsy rates. We also assessed kidney function and adherence to British Society for Allergy & Clinical Immunology (BSACI) recommendations for adrenaline autoinjector prescriptions.

A total of 51 patients (median age: 54 years, 16 male) with elevated baseline tryptase were reviewed. The median BST was 14.5 µg/L. Droplet digital PCR genotyping of the TPSAB1 gene was performed in 13 patients, with 10 testing positive. Twelve patients had BST values >20 µg/L; among them, nine were referred to haematology, and two had a confirmed HαT diagnosis. Among 47 patients assessed with REMA scoring, six had a score ≥2. Of these, four underwent haematology assessments, and one was confirmed to have HαT. Renal function was not assessed as a potential contributing factor in 16% of patients. Adrenaline autoinjectors were prescribed for 37% of patients in accordance with BSACI guidelines. Among patients with HαT, drug-related allergy was the most common clinical presentation, observed in seven patients. Other presentations included food allergy, venom allergy and chronic urticaria.

This evaluation underscores inconsistencies in follow-up practices and diagnostic pathways for patients with elevated BST. Although HαT genetic testing offers insights into a hereditary trait, its direct clinical impact and implications for patient management remain uncertain. Developing standardized protocols that integrate allergy, immunology, and haematology services is crucial to optimizing patient care, minimizing unnecessary investigations, and ensuring early detection of clonal mast cell disorders.