Short-term biological variation of serum tryptase.

OBJECTIVES: Serum tryptase is a biomarker of mast cell activation. Among others, it is used in the diagnosis of anaphylaxis where a significant increase during the acute phase supports the diagnosis. When evaluating changes in biomarker levels, it is of utmost importance to consider the biological variation of the marker. Therefore, the aim of this study was to evaluate the short-term biological variation of serum tryptase. METHODS: Blood samples were drawn at 9 AM three days in a row from apparently healthy subjects. On day two, additional blood samples were drawn every third hour for 12 h. The tryptase concentration was measured in serum using a fluoroenzyme immunoassay (ImmunoCAP™, Thermo Fisher Scientific). Linear mixed-effects models were used to calculate components of biological variation. RESULTS: In 32 subjects, the overall mean concentration of tryptase was 4.0 ng/mL (range, 1.3-8.0 ng/mL). The within-subject variation was 3.7 % (95 % confidence interval (CI) 3.0-4.4 %), the between-subject variation was 31.5 % (95 % CI 23.1-39.8 %), and the analytical variation was 3.4 % (95 % CI 2.9-4.1 %). The reference change value was 13.3 % for an increase in tryptase at a 95 % level of significance. No significant day-to-day variation was observed (p=0.77), while a minute decrease in the serum concentration was observed during the day (p<0.0001). CONCLUSIONS: Serum tryptase is a tightly regulated biomarker with very low within-subject variation, no significant day-to-day variation, and only minor semidiurnal variation. In contrast, a considerable between-subject variation exists. This establishes serum tryptase as a well-suited biomarker for monitoring.

Reference intervals for platelet large cell ratio, platelet distribution width, plateletcrit and standard haematological parameters determined on the Sysmex XN-10 in a cohort of 30,917 Danish blood donors.

With the introduction of the Sysmex XN-10, new platelet indices reflecting platelet maturity can be obtained alongside with a full blood count. Therefore, the need for verified reference intervals is present. The purpose of this study was to establish reference intervals for the platelet indices: platelet large cell ratio (P-LCR), platelet distribution width (PDW) and plateletcrit (PCT) in a large Scandinavian cohort. Furthermore, we aimed to verify previously established reference intervals of haematological parameters included in a full blood count. Blood samples were obtained from healthy Danish blood donors and analysed by use of the Sysmex XN-10 analyser (Sysmex, Kobe, Japan). Non-parametric 95% reference intervals were determined as the 2.5 and 97.5 percentile and presented with 90% confidence intervals (CI). In total, 30,917 blood donors were included and the following reference intervals were established: P-LCR, ratio: 17.3 (90% CI: 17.2 - 17.5) - 46.2 (90% CI:45.9 - 46.4); P DW, fL:9.5 (90% CI: 9.5 - 9.5) - 17.2 (90% CI: 17.2 - 17.3) and PCT, fraction: 0.18 (0.18 - 0.18) - 0.38 (0.38 - 0.39). The reference intervals were stable across age and sex. Furthermore, reference intervals for the remaining haematological parameters included in a full blood count were verified and found in line with the previously established reference intervals.

Pediatric reference intervals of the hemoglobin fractions HbA2, HbF and HbA0 using high-performance liquid chromatography and capillary electrophoresis.

INTRODUCTION: ß-thalassemia is a common genetic disorder with an estimated prevalence of 80-90 million carriers worldwide. As elevated hemoglobin A2 (HbA2) is a primary feature of carriers, hemoglobin fraction analysis is a common technique used for initial screening. However, pediatric reference intervals (RIs) are scarce. Hence, the aim was to establish pediatric RIs of hemoglobin fractions using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). METHODS: Samples were collected from assumed healthy children and adolescents of 1-18 years. Analyses were conducted using the Tosoh Automated Glycohemoglobin Analyzer HLC-723®G11 (Tosoh G11, HPLC) and the Capillarys 3 Octa (CE). Data were investigated for need of partitioning by both age (1-6 years vs. 6-18 years) and sex. RESULTS: In total, 189 and 196 subjects were included in the statistical analysis of HPLC and CE, respectively. The 95% RI of HbA2 was 2.00-2.90% by HPLC and 2.2-3.0% by CE. Partitioning of data was not clinically relevant by HPLC. However, partitioning by age was suggested by CE. CONCLUSION: RIs of hemoglobin fractions in individuals of 1-18 years using commercially available HPLC and CE equipment were reported. This is the first report of a pediatric RI of HbA2 using the Tosoh G11.