Background: Patients with chronic kidney disease have been reported to have increased concentrations of blood tryptase. Detection of tryptase in the urine of healthy subjects has been reported. Objective: The objective is to determine whether tryptase is indeed cleared by the kidneys. Methods: Blood and urine collections were performed in healthy and systemic mastocytosis subjects. Total and mature tryptase concentrations in blood and total tryptase concentrations in urine were determined. Results: Total tryptase levels in urine were below the limit of detection in both healthy subjects and those with systemic mastocytosis, even after concentrating the urine 10-fold. Thus, both mature and protryptase levels in urine are
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