Tryptase is not cleared by the kidneys into the urine.

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 <0.2 ng/ml.

Conclusion: Tryptase is not cleared by the kidneys into the urine.