Nearly half of patients who have near-normal tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. levels when they are diagnosed with systemic mastocytosis (SM) may later see these levels rise, found a study recently published in The Journal Allergy and Clinical Immunology: In Practice.
Tryptase is an enzyme made by mast cells. In people without SM, the amount of tryptase in the blood — called basal serum tryptase (BST) level — is generally less than 11.5 ng/mL. Having a BST level of 20 ng/mL or higher is a signpost that points to an SM diagnosis.
Understanding serum tryptase and systemic mastocytosis: What patients should know
However, approximately 16% to 30% of patients with a confirmed SM diagnosis have tryptase levels below this 20 ng/mL threshold. To better understand long-term trajectories in this group, the authors investigated BST levels in patients who initially presented with lower levels.
The study identified 107 individuals with a confirmed SM diagnosis within Kaiser Permanente Southern California. Overall, 20 individuals (20.6%) presented with a baseline BST below 20 ng/mL. Of these, 18 participants were included in the analysis and followed for a median of 47 months.
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Participants had an average initial BST level of 13.1 ng/mL, and seven had a BST level that wasn’t elevated beyond the normal range at all. During follow-up, one of these seven patients saw a rise in BST levels that reached the 20 ng/mL SM threshold. Among the 11 patients with a baseline BST between 11.4 ng/mL and 20 ng/mL, seven (63.6%) later developed levels greater than or equal to 20 ng/mL.
On average, it took 15 months for patients to reach a BST level of 20 ng/mL or higher. The median peak BST was 28.3 ng/mL among those who surpassed the threshold. Many individuals displayed gradual increases in BST over time, suggesting that repeat testing may help to uncover trends with time.
These findings highlight the importance of considering other diagnostic measures alongside BST in cases of suspected SM. Due to its small sample size, the study did not investigate associations with measures of disease burden, quality of life or mutation status.
“Larger prospective studies with standardized longitudinal assessments are needed to evaluate these relationships and determine the clinical significance of changes in BST over time,” the authors concluded.
