European Biological Variation Study (EuBIVAS): within- and between-subject biological variation estimates of ß-isomerized C-terminal telopeptide of type I collagen (ß-CTX), N-terminal propeptide of type I collagen (PINP), osteocalcin, intact fibroblast growth factor 23 and uncarboxylated-unphosphorylated matrix-Gla protein-a cooperation between the EFLM Working Group on Biological Variation and the International Osteoporosis Foundation-International Federation of Clinical Chemistry Committee on Bone Metabolism.

We have calculated the biological variation (BV) of different bone metabolism biomarkers on a large, well-described cohort of subjects. BV is important to calculate reference change value (or least significant change) which allows evaluating if the difference observed between two consecutive measurements in a patient is biologically significant or not. INTRODUCTION: Within-subject (CVI) and between-subject (CVG) biological variation (BV) estimates are essential in determining both analytical performance specifications (APS) and reference change values (RCV). Previously published estimates of BV for bone metabolism biomarkers are generally not compliant with the most up-to-date quality criteria for BV studies. We calculated the BV and RCV for different bone metabolism markers, namely ß-isomerized C-terminal telopeptide of type I collagen (ß-CTX), N-terminal propeptide of type I collagen (PINP), osteocalcin (OC), intact fibroblast growth factor 23 (iFGF-23), and uncarboxylated-unphosphorylated Matrix-Gla Protein (uCuP-MGP) using samples from the European Biological Variation Study (EuBIVAS). METHODS: In the EuBIVAS, 91 subjects were recruited from six European laboratories. Fasting blood samples were obtained weekly for ten consecutive weeks. The samples were run in duplicate on IDS iSYS or DiaSorin Liaison instruments. The results were subjected to outlier and variance homogeneity analysis before CV-ANOVA was used to obtain the BV estimates. RESULTS: We found no effect of gender upon the CVI estimates. The following CVI estimates with 95% confidence intervals (95% CI) were obtained: ß-CTX 15.1% (14.4-16.0%), PINP 8.8% (8.4-9.3%), OC 8.9% (8.5-9.4%), iFGF23 13.9% (13.2-14.7%), and uCuP-MGP 6.9% (6.1-7.3%). CONCLUSIONS: The EuBIVAS has provided updated BV estimates for bone markers, including iFGF23, which have not been previously published, facilitating the improved follow-up of patients being treated for metabolic bone disease.

Systematic review of the biological variation data for diabetes related analytes.

BACKGROUND: Objective interpretation of laboratory test results used to diagnose and monitor diabetes mellitus in part requires the application of biological variation data (BVD). The quality of published BVD has been questioned. The aim of this study was to quality assess publications reporting BVD for diabetes-related analytes using the Biological Variation Data Critical Appraisal Checklist (BIVAC); to assess whether published BVD are fit for purpose and whether the study design and population attributes influence BVD estimates and to undertake a meta-analysis of the BVD from BIVAC-assessed publications. METHODS: Publications reporting data for glucose, HbA1c, adiponectin, C-peptide, fructosamine, insulin like growth factor 1 (IGF-1), insulin like growth factor binding protein 3 (IGFBP-3), insulin, lactate and pyruvate were identified using a systematic literature search. These publications were assessed using the BIVAC, receiving grades A, B, C or D, where A is of highest quality. A meta-analysis of the BVD from the assessed studies utilised weightings based upon BIVAC grades and the width of the data confidence intervals to generate global BVD estimates. RESULTS: BIVAC assessment of 47 publications delivered 1 A, 3 B, 39C and 4 D gradings. Publications relating to adiponectin, C-peptide, IGF-1, IGFBP-3, lactate and pyruvate were all assessed as grade C. Meta-analysis enabled global BV estimates for all analytes except pyruvate, lactate and fructosamine. CONCLUSIONS: This study delivers updated and evidence-based BV estimates for diabetes-related analytes. There remains a need for delivery of new high-quality BV studies for several clinically important analytes.

Age of the intronic GAA triplet repeat expansion mutation in Friedreich ataxia.

Friedreich ataxia (FRDA), the most frequently inherited ataxia, is due in the vast majority of cases to a large expansion of an intronic GAA repeat. Using linkage disequilibrium analysis based on haplotype data of seven polymorphic markers close to the frataxin gene, the age of FRDA founding mutational event(s) is estimated to be at least 682+/-203 generations (95% confidence interval: 564-801 g), a dating which is consistent with little or no negative selection and provides further evidence for an ancient spread of a pre-mutation (at-risk alleles) in western Europe.

Age and origin of the FCMD 3'-untranslated-region retrotransposal insertion mutation causing Fukuyama-type congenital muscular dystrophy in the Japanese population.

Fukuyama-type congenital muscular dystrophy (FCMD), an autosomal recessive disorder with a high prevalence in the Japanese population, is characterised by severe muscular dystrophy associated with brain malformation (cortical dysgenesis) and mental retardation. In Japan, 87% of FCMD-bearing chromosomes carry a 3-kb retrotransposal insertion of tandemly repeated sequences within the disease gene recently identified on chromosome 9q31, and most of them share a common founder haplotype. FCMD is the first human disease known to be caused primarily by an ancient retrotransposal integration. By applying two methods for the study of linkage disequilibrium between flanking polymorphic markers and the disease locus, and of its decay over time, the age of the insertion mutation causing FCMD in Japanese patients is calculated to be approximately 102 generations (95% confidence interval: 86-117 g), or slightly less. The estimated age dates the most recent common ancestor of the mutation-bearing chromosomes back to the time (or a few centuries before) the Yayoi people started migrating to Japan from the Korean peninsula. This finding makes the molecular population genetics of FCMD understandable in the context of Japan's history and the founder effect consistent with the prevalent theory on the origins of the modern Japanese population.

Multicentre evaluation of KONE Optima analysis system.

Optima from KONE Instruments Corporation is a new selective laboratory analyzer for turbidimetric, colorimetric and ion selective electrode measurements. Overall analytical performance of Optima and reagents provided by KONE was evaluated according to ECCLS guidelines, in a multicentre study involving four different laboratories, including substrates (cholesterol, high-density lipoprotein-cholesterol, creatinine), specific proteins (transferrin, IgG), enzyme activities (gamma-glutamyltransferase, alanine aminotransferase) and electrolytes (sodium, potassium, chloride). The results obtained attest good precision of the system for all the analytes tested: the range of within-run CV is 0.5 %-4.3 %, and range of between-day CV % is 0.8 %-7.9 % (median of four laboratories). Except for total cholesterol (5 % overestimation compared to the reference method) accuracy of measurement is adequate. Creatinine and uric acid assays were subjects of interference (defined as deviation > 10 % from target value) by bilirubin and haemoglobin respectively.

Creatinine measurement proficiency testing: assignment of matrix-adjusted ID GC-MS target values.

The results of an external quality-assessment experiment for serum creatinine measurement are described. Fifty-one laboratories performed quintuplicate analyses during three different analytical runs on six lyophilized sera and two frozen human serum pools. Isotope dilution gas chromatography-mass spectrometry (ID GC-MS) target values were assigned to all the materials. Intralaboratory within- and between-run imprecision results were very similar for all the materials tested (CV < or = 2.20% and < or = 4.70%, respectively). The overall imprecision obtained was high (CV 6.5-20.0%) because of increased interlaboratory-intermethod variability. A significant positive bias (+ 9.2-+43.7%) was found for all the materials at lower creatinine concentration. By using two human sera at different concentrations, we could calculate the constant and the proportional calibration bias displayed by each peer group. The majority of the lyophilized materials showed a behavior divergent from the frozen pools, indicating matrix-related problems. We propose a new algorithm for calculating matrix bias correction factor instrument-reagent specific for each material.

Accuracy of cholesterol measurements in Italian clinical laboratories. Joint project GISSI prevention--Italian Society of Clinical Biochemistry. SIBioC GISSI Prevenzione Group.

We report the results of an external quality assessment scheme for serum total cholesterol measurement involving about 100 Italian laboratories participating in an epidemiological study of post myocardial infarction. Two frozen human serum pools with Abell-Kendall assigned values are distributed quarterly at the laboratories (up to now seven events occurred); the obtained results are evaluated and discussed. In one exercise (# 5) duplicated measurements were repeated on three different days. Eighty-five to 98% of the laboratories obtained results within the total error limits (+/- 8.9%). But, while precision (calculated on the six replicates of exercise # 5) is good (90% of the laboratories obtained CV < 3%), inaccuracy problems are evident in every event. Indeed the mean bias from the reference method value ranged from 1.54 and 3.49% in the various events.

Behavior of frozen serum pools and lyophilized sera in an external quality-assessment scheme.

To further improve analytical accuracy in clinical chemistry, proficiency testing needs amelioration in the quality of materials tested and in target value assignment. To obtain information on the actual state-of-the-art in the Lombardy region of Italy, and to examine the behavior of different types of control materials (fresh-frozen human sera and lyophilized materials), we developed the following experimental design. Two human serum pools and two lyophilized sera were distributed to 32 laboratories for determination of glucose, creatinine, cholesterol, sodium, potassium, and gamma-glutamyltransferase (gamma-GT). Each analyte was measured in triplicate on each of 3 days. Target values for the controls were obtained with Reference Methods. The results show a good intralaboratory precision for every component but some accuracy problems for glucose, creatinine, cholesterol, and gamma-GT. Lyophilized materials showed some commutability problems for glucose, electrolytes, and gamma-GT, mainly with dry chemistry technology.