Updated total IgE reference intervals in Norwegian adults.

BACKGROUND: It is important and expected of laboratories to provide updated reference intervals to the clinician. As no recent publications report adult total IgE reference intervals on a Scandinavian population, the aim of our study was therefore to provide an estimate on healthy Norweigian adults. METHODS: A reference interval study was conducted in accordance to CLSI guidelines. Samples were collected from n = 252 presumably healthy adult participants enrolled through the regional blood donation program. Total IgE measurements were performed on the ImmunoCAPTM platform (Thermo Fisher Diagnostics) traceable to the WHO-reference standard (75/502) for total IgE measurements. RESULTS: An upper 95% total IgE reference limit was estimated to 302 kU/L (90% CI 177-388 kU/L), and the 97.5% percentile was estimated to 391 kU/L (90% CI 344-560 kU/L). No significant differences were found between participants who self-reported having an allergic disease and participants who did not self-report having an allergic disease. CONCLUSION: Our results and other recent publications find markedly higher values than adult reference intervals established four decades ago which still remain widely used by clinical laboratories. We therefore recommend total IgE reference intervals should be critically reviewed and updated.

Estimating the within-subject (CVI ) and between-subject (CVG ) biological variation of serum tryptase.

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.