The potential clinical utility of serum alpha-protryptase levels

Background: Because biopsy criteria for diagnosing systemic mastocytosis ar e not precise, the value of serum alpha-protryptase levels in the work-up o f suspected systemic mastocytosis should be considered. Objective: A retrospective analysis was performed on subjects with total tr yptase serum levels that were high (greater than or equal to 20 ng/mL), whi le beta-tryptase serum levels were normal (<1 ng/mL) or modestly elevated ( 1 to 5 ng/mL). Methods: Over a 3.5-year period, 52 qualifying specimens mere identified fr om 1369 consecutive samples. The corresponding subjects were divided into t hose with suspected mastocytosis and those with suspected anaphylaxis. Subj ects with suspected mastocytosis were subdivided into 3 subgroups on the ba sis of biopsy results (positive, negative, or not available). Subjects with suspected anaphylaxis were subdivided into living and deceased subgroups. Results: Among the 15 subjects who underwent biopsy, alpha-protryptase seru m levels (the difference between directly-measured levels of serum total tr yptase and beta-tryptase), when greater than 75 ng/mL (n = 9), were always associated with a positive biopsy result for systemic mastocytosis; levels from 20 to 75 ng/mL (n = 6) were associated with a positive biopsy resort i n 50% of subjects. alpha-Protryptase serum levels may be a more sensitive s creening test than a bone marrow biopsy for this disorder. Also, elevated a lpha-protryptase serum levels in some adult patients return to normal over time, suggesting that mast cell hyperplasia resolved in these patients. Fin ally, a high alpha-protryptase level may reveal anaphylaxis to be a present ing manifestation of systemic mastocytosis or mast cell hyperplasia. Conclusion: Levels of serum alpha-protryptase, relative to those of beta-tr yptase, appear to be useful in the diagnostic work-up and follow-up of subj ects with suspected systemic mastocytosis.