Comparison of Enzymatic Assay for HBA1C Measurement (Abbott Architect) With Capillary Electrophoresis (Sebia Minicap Flex Piercing Analyser)

Objective

To compare the analytical performances of the enzymatic method (EM) and capillary electrophoresis (CE) for hemoglobin A1c (HbA1c) measurement.

Methods

Imprecision, carryover, stability, linearity, method comparison, and interferences were evaluated for HbA1c via EM (Abbott Laboratories, Inc) and CE (Sebia).

Results

Both methods have shown overall within-laboratory imprecision of less than 3% for International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (<2% National Glycohemoglobin Standardization Program [NGSP] units). Carryover effects were within acceptable criteria. The linearity of both methods has proven to be excellent (R2 = 0.999). Significant proportional and constant difference were found for EM, compared with CE, but were not clinically relevant (<5 mmol/mol; NGSP <0.5%). At the clinically relevant HbA1c concentration, stability observed with both methods was acceptable (bias, <3%). Triglyceride levels of 8.11 mmol per L or greater showed to interfere with EM and fetal hemoglobin (HbF) of 10.6% or greater with CE.

Conclusion

The enzymatic method proved to be comparable to the CE method in analytical performances; however, certain interferences can influence the measurements of each method.

Recommendation for the review of biological reference intervals in medical laboratories

This document is based on the original recommendation of the Expert Panel on the Theory of Reference Values of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), updated guidelines were recently published under the auspices of the IFCC and the Clinical and Laboratory Standards Institute (CLSI). This document summarizes proposals for recommendations on: (i) The terminology, which is often confusing, noticeably concerning the terms of reference limits and decision limits. (ii) The method for the determination of reference limits according to the original procedure and the conditions, which should be used. (iii) A simple procedure allowing the medical laboratories to fulfill the requirements of the regulation and standards. The updated document proposes to verify that published reference limits are applicable to the laboratory involved. Finally, the strengths and limits of the revised recommendations (especially the selection of the reference population, the maintenance of the analytical quality, the choice of the statistical method used…) will be briefly discussed.

Flexible scope for ISO 15189 accreditation: a guidance prepared by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group Accreditation and ISO/CEN standards (WG-A/ISO)

The recent revision of ISO15189 has further strengthened its position as the standard for accreditation for medical laboratories. Both for laboratories and their customers it is important that the scope of such accreditation is clear. Therefore the European co-operation for accreditation (EA) demands that the national bodies responsible for accreditation describe the scope of every laboratory accreditation in a way that leaves no room for doubt about the range of competence of the particular laboratories. According to EA recommendations scopes may be fixed, mentioning every single test that is part of the accreditation, or flexible, mentioning all combinations of medical field, examination type and materials for which the laboratory is competent. Up to now national accreditation bodies perpetuate use of fixed scopes, partly by inertia, partly out of fear that a too flexible scope may lead to over-valuation of the competence of laboratories, most countries only use fixed scopes. The EA however promotes use of flexible scopes, since this allows for more readily innovation, which contributes to quality in laboratory medicine. In this position paper, the Working Group Accreditation and ISO/CEN Standards belonging to the Quality and Regulation Committee of the EFLM recommends using an approach that has led to successful introduction of the flexible scope for ISO15189 accreditation as intended in EA-4/17 in The Netherlands. The approach is risk-based, discipline and competence-based, and focuses on defining a uniform terminology transferable across the borders of scientific disciplines, laboratories and countries.

Accreditation process in European countries – an EFLM survey

Accreditation is a valuable resource for medical laboratories. The development of quality systems based on ISO 15189 has taken place in many laboratories in the European countries but data about accreditation remain scarce. The EFLM Working Group “Accreditation and ISO/CEN standards” conducted a survey that reviews the current state of the accreditation process in European countries.

An on-line questionnaire was addressed to delegates of 39 EFLM scientific societies in March 2014. One answer by country was taken into account. The survey was dealing with mandatory status, number of accredited medical laboratories in each country, possibility of flexible scope and concerned medical fields. The status of point-of-care testing (POCT) in each country was also studied.

Twenty-nine responses (74%) were registered. All the assessed countries (100%) have begun an accreditation process in various ways. All the national accreditation bodies (NAB) offer or are working to offer an ISO 15189 accreditation. The accreditation process most often concerns all phases of the examination and various medical fields. Medical laboratories are responsible for POCT in 20 (69%) countries. The accreditation process for POCT, according to ISO 15189 and ISO 22870, is also developing.

While there are several variations in the approaches to accreditation of medical laboratories in the European countries, the ISO 15189 accreditation project has been widely accepted. The use of a unique standard and the cooperation among countries due to scientific societies, EFLM, accreditation bodies and EA enable laboratory professionals to move toward uniform implementation of the accreditation concept.

The role of classic risk factors and prothrombotic factor gene mutations in ischemic stroke risk development in young and middle-aged individuals

BACKGROUND

In young individuals, a genetically predisposing hypercoagulability and classic modifying risk factors can act synergistically on the ischemic stroke risk development. The aim of the study was to compare the prevalence of classic vascular risk factors and polymorphisms of the G20210A coagulation factor II (prothrombin), Arg506Glu coagulation factor V Leiden, C677T methylenetetrahydrofolate reductase (MTHFR), and 4G/5G plasminogen activator inhibitor-1 (PAI-1) and the impact of these gene mutations and classic vascular risk factors on the overall stroke risk in individuals aged 55 years or younger.

METHODS

The study included 155 stroke patients aged 55 years or younger and 150 control subjects. Stroke prevalence and odds ratio (OR) were assessed for the following parameters: G20210A prothrombin, Arg506Glu factor V Leiden, C677T MTHFR, and 4G/5G PAI-1 polymorphisms; total number of study polymorphisms in a particular subject (genetic sum); and classic vascular risk factors of hypertension, obesity, diabetes mellitus, cigarette smoking, hypercholesterolemia, hypertriglyceridemia, and elevated levels of low-density lipoprotein (LDL) cholesterol and very low-density lipoprotein cholesterol.

RESULTS

The prevalence of hypertension (P < .001), smoking (P < .001), decreased HDL cholesterol levels (P < .001), obesity (P = .001), elevated LDL cholesterol (P = .036), C677T MTHFR polymorphism (P < .001), and genetic sum was significantly higher in the group of stroke patients. The following parameters were found to act as independent risk factors for ischemic stroke: decreased HDL cholesterol level (P < .001; OR 4.618; 95% confidence interval [CI] 2.381-8.957); hypertension (P = .001; OR 2.839; 95% CI 1.519-5.305); obesity (P = .040; OR 2.148; 95% CI 1.036-4.457); smoking (P = .001; OR 2.502; 95% CI 1.436-4.359); and genetic sum as a continuous variable (P < .01; OR 2.307; 95% CI 1.638-3.250).

CONCLUSIONS

Gene mutations of the procoagulable and proatherosclerotic factors investigated exerted a synergistic action in the development of overall risk of ischemic stroke in young and middle-aged individuals.

The prevalence of preanalytical errors in a Croatian ISO 15189 accredited laboratory

BACKGROUND

The preanalytical phase is the most common source of laboratory errors. The goal of this descriptive study was to analyze the prevalence and type of preanalytical errors in relation to the site of sample collection (inpatient vs. outpatient) and the type of laboratory unit (hematology and coagulation vs. biochemistry). For the biochemistry unit, the data were also analyzed relative to the type of the analysis (stat vs. routine).

METHODS

We retrospectively analyzed the sample and test request form error rate for a 1-year period, from January to December 2008.

RESULTS

The frequency of the sample errors differed significantly between the emergency and routine biochemistry unit (0.69% vs. 2.14%; p<0.0001), and between inpatients and outpatients (1.12% vs. 1.36%; p=0.0006). Hemolysis was the most frequent sample error, accounting for 65% of all unsuitable specimens in the emergency biochemistry unit. The total sample error rate did not differ between hematology and coagulation vs. the biochemistry unit. The frequency of test request form errors differed significantly with respect to the sample collection site (p<0.0001), laboratory unit (p<0.0001) and type of the analysis (p<0.0001). Errors in the test request form were least frequent in the outpatient unit (2.98%) and most frequent in the routine biochemistry unit (65.94%).

CONCLUSIONS

Sample and test request form errors in our laboratory are occurring with a frequency comparable to that reported by others. Continuous educational action is needed for all stakeholders involved in laboratory testing to improve the quality of the preanalytical phase of the total testing process.

Matrix metalloproteinases and their inhibitors in different acute stroke subtypes

The aim of the study was to determine serum levels of selected matrix metalloproteinases (MMPs) and their natural inhibitors (TIMPs) in the acute phase of different stroke types subdivided according to the Oxfordshire Community Stroke Project (OCSP) classification and the possibility of discriminating stroke types according to their levels. The study included 126 patients with acute stroke within the first 24h of symptom onset, and 124 healthy volunteers. The stroke group had lower MMP-2 concentrations and MMP-2/TIMP-2 ratios (p<0.001) but higher TIMP-2 (p<0.001) than controls. The level of MMP-9 and the MMP-9/TIMP-1 ratio were higher in patients with total anterior circulation infarct (TACI) than in patients with other stroke subtypes according to OCSP classification (p=0.0019, p=0.0065, respectively) or in controls (p<0.0001, p=0.0024, respectively). A negative correlation of MMP-2 levels with MMP-9 and MMP-9/TIMP-1 ratio was recorded in all stroke subtypes except for TACI. Receiver operating characteristic analysis showed similar discriminating power for MMP-9 levels and Barthel index in the differential diagnosis of TACI. High MMP-9/TIMP-1 ratio (odds ratio 3.263) was associated with TACI. Our results demonstrate that the MMP-9/TIMP-1 ratio may provide information to help in assessing stroke patients in the future as a baseline biomarker of infarct extent.