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.publishedVersio

Biological variation of secretoneurin; a novel cardiovascular biomarker implicated in arrhythmogenesis

Background Secretoneurin is a novel prognostic biomarker that may predict mortality in heart failure and the occurrence of ventricular arrhythmias. This study reports the within subject variation (CVI), between subject variation (CVG), reference change values (RCV) and index of individuality (II) of secretoneurin. Methods Thirty healthy volunteers were included. Non-fasting samples were obtained between 8 and 10 am once a week for ten weeks. Secretoneurin was analyzed in duplicate using ELISA. No outliers were present according to Burnett and Reeds‘ criteria. Simple linear regression did not identify significant trends. Variance homogeneity in the analytical variance and CVI were tested using Cochrane’s and Bartlett’s tests and four participants were excluded. Calculation of CVI, CVG and RCV were done on ln transformed data as described by Fokkema, the II was calculated using retransformed data. Results The median age of the participants was 36 years and 53% were female. Non-fasting glucose, eGFR(CKD-EPI), cTnT and NT-proBNP concentrations were within the normal range. Median secretoneurin concentrations were 38 pmol/L (women) and 33 pmol/L (men), p-value < 0.001. CVI and CVG were 9.8% (CI 8.7% to 11.0%) and 20.0 (CI 15.4% to 28.0%), respectively. RCV were 38.7% (CI 35.5% to 42.7%) and −27.9 (CI −29.9 to −26.2) and the II were 0.60 (CI 0.42–0.78). No gender differences were present. Conclusion Secretoneurin has a fairly low CVI, CVG, RCV and II, indicating that it could be suitable as a diagnostic or prognostic biomarker and that delta values in serial samplings may be preferable for identifying clinical changes.publishedVersio

Estimation of Preanalytical Uncertainty in Clinical Chemistry

Preanalytical uncertainty is attributable to variations in blood sample collection and sample handling before analysis. The aim of this study was to establish a modelling framework for estimating preanalytical uncertainty. There is a need for standardization on which uncertainty sources that should be included, and how the preanalytical uncertainty should be estimated. In Paper I, an uncertainty budget was established based on differences in paired data between a standard method for handling blood samples and alternative methods used in current practice, considering the distribution of alternative methods. In Paper II and III, linear mixed-effects models were used to estimate the between-venipuncture SD, the preanalytical SD (excluding the betweenvenipuncture SD), and the measurement repeatability when the phlebotomy and the sample handling were performed optimally, and any difference in preanalytical SD and fixed effects, between transporting blood samples in a pneumatic tube system vs manual delivery, using different needles or tubes, and mixing methods. When the combined biases from the uncertainty budget in Paper I and the significant biases between different treatments in Paper II and III were compared with defined quality specifications for analytical bias, glucose was the only analyte falling outside the quality specifications. Prolonged clotting and storage time were the greatest contributors to the bias for glucose, and the significant mean difference between SST vs RST tubes shows that choice of tube is important. The preanalytical SDs (excluding the between-venipuncture SD) for LD and potassium for optimally treated samples, were significantly higher than the measurement repeatability SDs, but for glucose, the between-venipuncture SD was the dominant source of variation. For most analytes, the preanalytical SDs were about the same in both studies II and III, indicating that the preanalytical variations are little influenced by different preanalytical handling. We have developed two models that can be used to estimate preanalytical uncertainty in clinical chemistry laboratories. Estimation of preanalytical uncertainty may improve diagnostic quality and patient treatment

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

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.publishedVersio

Biological variation of secretoneurin; a novel cardiovascular biomarker implicated in arrhythmogenesis

Background Secretoneurin is a novel prognostic biomarker that may predict mortality in heart failure and the occurrence of ventricular arrhythmias. This study reports the within subject variation (CVI), between subject variation (CVG), reference change values (RCV) and index of individuality (II) of secretoneurin. Methods Thirty healthy volunteers were included. Non-fasting samples were obtained between 8 and 10 am once a week for ten weeks. Secretoneurin was analyzed in duplicate using ELISA. No outliers were present according to Burnett and Reeds‘ criteria. Simple linear regression did not identify significant trends. Variance homogeneity in the analytical variance and CVI were tested using Cochrane’s and Bartlett’s tests and four participants were excluded. Calculation of CVI, CVG and RCV were done on ln transformed data as described by Fokkema, the II was calculated using retransformed data. Results The median age of the participants was 36 years and 53% were female. Non-fasting glucose, eGFR(CKD-EPI), cTnT and NT-proBNP concentrations were within the normal range. Median secretoneurin concentrations were 38 pmol/L (women) and 33 pmol/L (men), p-value < 0.001. CVI and CVG were 9.8% (CI 8.7% to 11.0%) and 20.0 (CI 15.4% to 28.0%), respectively. RCV were 38.7% (CI 35.5% to 42.7%) and −27.9 (CI −29.9 to −26.2) and the II were 0.60 (CI 0.42–0.78). No gender differences were present. Conclusion Secretoneurin has a fairly low CVI, CVG, RCV and II, indicating that it could be suitable as a diagnostic or prognostic biomarker and that delta values in serial samplings may be preferable for identifying clinical changes

Sex Hormones and Adrenal Steroids : Biological Variation Estimated Using Direct and Indirect Methods

Background Biological variation (BV) data may be used to develop analytical performance specifications (APS), reference change values (RCV), and support the applicability of population reference intervals. This study estimates within-subject BV (CVI) for several endocrine biomarkers using 3 different methodological approaches. Methods For the direct method, 30 healthy volunteers were sampled weekly for 10 consecutive weeks. Samples were analyzed in duplicate for 17-hydroxyprogesterone (17-OHP), androstenedione, cortisol, cortisone, estradiol, follicle-stimulating hormone (FSH), luteinizing hormone (LH), sex hormone-binding globulin (SHBG), and testosterone. A CV-ANOVA with outlier removal and a Bayesian model were applied to derive the CVI. For estradiol, FSH and LH, only the male subgroup was included. In the indirect method, using the same analytes and groups, pairs of sequential results were extracted from the laboratory information system. The total result variation for individual pairs was determined by identifying a central gaussian distribution in the ratios of the result pairs. The CVI was then estimated by removing the effect of analytical variation. Results The estimated CVI from the Bayesian model (mu CVP(i)) in the total cohort was: 17-OHP, 23%; androstenedione, 20%; cortisol, 18%; cortisone, 11%; SHBG, 7.4%; testosterone, 16%; and for the sex hormones in men: estradiol, 14%; FSH, 8%; and LH, 26%. CVI-heterogeneity was present for most endocrine markers. Similar CVI data were estimated using the CV-ANOVA and the indirect method. Conclusions Similar CVI data were obtained using 2 different direct and one indirect method. The indirect approach is a low-cost alternative ensuring implementation of CVI data applicable for local conditions.Funding Agencies|Haukeland University Hospital; BritishHeart Foundation [FS/18/78/33902]; Guys and St ThomasCharity (London, UK) [R060701, R100404]; Haukeland University Hospital, Department ofMedical Biochemistry and Pharmacology; University of Oslo</p

Improving quality in the preanalytical phase through innovation, on behalf of the European Federation for Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for Preanalytical Phase (WG-PRE)

It is now undeniable that laboratory testing is vital for the diagnosis, prognostication and therapeutic monitoring of human disease. Despite the many advances made for achieving a high degree of quality and safety in the analytical part of diagnostic testing, many hurdles in the total testing process remain, especially in the preanalytical phase ranging from test ordering to obtaining and managing the biological specimens. The Working Group for the Preanalytical Phase (WG-PRE) of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) has planned many activities aimed at mitigating the vulnerability of the preanalytical phase, including the organization of three European meetings in the past 7 years. Hence, this collective article follows the previous three opinion papers that were published by the EFLM WGPRE on the same topic, and brings together the summaries of the presentations that will be given at the 4th EFLM-BD meeting "Improving quality in the preanalytical phase through innovation" in Amsterdam, 24-25 March, 2017.status: publishe