Hereditary-alpha tryptasemia (HαT) is the most common etiology for elevated basal serum tryptase (BST). However, the utility of tryptase genotyping of individuals with elevated BST in general clinical practice remains undefined. Moreover, studies showing associations between elevated BST and chronic kidney disease (CKD), myelodysplastic syndrome (MDS), rheumatoid arthritis (RA), or eosinophilic esophagitis (EoE) did not include tryptase genotyping.
To determine the utility of tryptase genotyping among individuals with moderate elevations in BST at a regional health system.
Clinical and laboratory data from 109 subjects with basal tryptase values ≥ 7.5 ng/mL who were tested for HαT or had a disorder previously linked to elevated BST were collected retrospectively by chart review.
58 subjects had elevated BST defined as ≥11.5 ng/mL. 63.8% (n=37/58) had HαT, 12.1% (n=7/58) had CKD, and 20.7% (n=12/58) had clonal myeloid disorders. 6.9% (n=4/58) of subjects with elevated BST had negative testing for HαT, CKD, and myeloid neoplasms. 2 subjects with CKD, 1 subject with MDS, and 1 with myeloid hypereosinophilic syndrome (HES) had negative testing for HαT. Among subjects with elevated BST and more than one tryptase measurement, 41.5% (n=22/53) had BST variability that exceeded the 20% plus 2 formula. Increased BST variability was found in subjects with HαT, all forms of mastocytosis, CKD, MDS, and those with no associated diagnosis.
HαT, CKD, and clonal myeloid disorders or a combination of the three constitute approximately 90% of individuals with elevated BST in clinical practice. Myeloid neoplasms were over-represented in this cohort relative to population prevalence data suggesting tryptase measurement selection bias by clinicians or higher prevalence. Elevated BST is associated with increased tryptase variability, regardless of etiology.

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