Abstract
BACKGROUND: Tryptase is used as a biomarker to support the diagnosis of anaphylaxis and hematologic diseases. In the event of a mast cell activation during anaphylaxis, a temporary increase in the concentration of tryptase may be seen. On the basis of clinical studies, an increase of 2 µg/L + 20% from basis level has been proposed as significant. To evaluate the increase in tryptase levels, the within-subject (CV(I) ) and between-subject (CV(G) ) biological variations should be known. This study was conducted to estimate the biological variation of tryptase and to identify the reference change value (RCV). METHODS: Blood samples were collected from healthy volunteers once a week consecutively over a 10-week period. Tryptase was measured by the use of a fluoroenzyme immunoassay (ImmunoCAP(TM) ; Thermo Fisher Scientific), and linear mixed-effects models were used to calculate the biological variation and RCV for both nontransformed and log-transformed tryptase. RESULTS: Fourteen presumably healthy young adults (six males and eight females, age 23-35 years) were included. The CV(I) was 5.6% and the CV(G) was 31.5% (nontransformed data). Log-transformed data showed similar results. The analytical variation (CV(A) ) was 6.3% and the RCV was 23.5%. CONCLUSIONS: Young healthy adults without ongoing allergic reactions show low within-subject biological variation. Higher biological variation was observed between subjects.