Tryptase genotyping in the evaluation of patients with elevated BST. Stepwise approach to a patient workup based on BST level and tryptase genotype using the BST CALCULATER. Myeloid neoplasms often exist in the absence of elevated BST; this algorithm is intended only to aid in the correct interpretation of elevated BST when other indications for workup are absent/nonspecific. AD, autosomal dominant; NGS, next-generation sequencing; ULN, upper limit of normal. ∗At the time of this publication, this is the only Clinical Laboratory Improvement Amendments/College of American Pathologists–certified laboratory performing tryptase genotyping. ^†Only α-tryptase–encoding TPSAB1 replications are associated with elevated BST and require correction. ^‡BST elevation is not a requirement for any clonal neoplasm, and evaluation should be guided by clinical presentation and findings. ^§Allele-specific PCR or ddPCR should be used because of low allelic frequency.