Estimating the within-subject (CVI ) and between-subject (CVG ) biological variation of serum tryptase
Birthe R Skarbø1, Erik W Vinnes1, Tore Wentzel-Larsen2,3,4
1Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Norway.
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 (CVI ) and between-subject (CVG ) 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 (ImmunoCAPTM ; 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 CVI was 5.6% and the CVG was 31.5% (nontransformed data). Log-transformed data showed similar results. The analytical variation (CVA ) 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.
