Diane Maisin

Automated serum protein electrophoresis by Capillarys.

Abstract Capillary zone electrophoresis (CZE) of serum proteins is increasingly gaining impact in clinical laboratories. In this report, we evaluate automated capillary zone electrophoresis by Capillarys® (Sebia, France). Withinrun and between-run imprecision for the five electrophoretic fractions was <2% and <6%, respectively. Data obtained with Capillarys correlated with results obtained with agarose gel electrophoresis and Paragon CZE® 2000 (Beckman Coulter, USA). Analysis of serum obtained from patients with inflammation, nephrotic syndrome, bisalbuminemia, and α1-antitrypsin deficiency revealed that Capillarys was able to detect these abnormalities. Two hundred thirty eight samples were analyzed by agarose gel electrophoresis, Capillarys, capillary electrophoresis using Paragon CZE 2000 system, and immunofixation. Sample selection was based on the presence of a disturbed morphology (e.g., spike) of the protein profile or hypogammaglobulinemia on agarose gel electrophoresis and/or Capillarys. Immunofixation revealed the presence of a monoclonal protein, oligoclonal bands, polyclonal pattern, and a normal profile in, respectively, 89, 66, 19, and 64 samples. With Capillarys, Paragon, and agarose gel electrophoresis, a spike and/or disturbed morphology of the profile was found in 222, 182, and 180 samples, respectively. In these samples, immunofixation was negative in 73 (33%), 46 (25%), and 39 (22%) samples, respectively. These data indicate that Capillarys has a lower specificity than agarose gel electrophoresis and Paragon 2000. Of the 89 samples with a monoclonal protein, Capillarys, Paragon, and agarose gel electrophoresis failed to detect, respectively, three, three, and one monoclonal protein(s). Interferences by radio-opaque agents, complement degradation products, fibrinogen, and triglycerides are described. In conclusion, automated capillary zone electrophoresis with Capillarys provides for reproducible, rapid, and reliable serum electrophoresis.

Multicentre evaluation of the Tosoh HbA1c G8 analyser

Abstract Background: We report a Dutch–Belgian multicentre evaluation of the Tosoh HLC-723G8 glycohaemoglobin analyser, an ion-exchange HPLC instrument for the separation and quantification of haemoglobin A1c (HbA1c) in whole blood. Methods: We evaluated the analytical performances of the Tosoh G8 analyser and compared the results for blood samples with its predecessor, the Tosoh G7, and with two other widely used analysers, the Bio-Rad Variant II and Adams Arkray HA-8160. Results: Within- and between-batch imprecision [coefficient of variation (CVs)] was <0.5% and 2%, respectively, and compared favourably with the G7. The excellent performances in terms of speed (1.6 min/analysis) did not result in increased variability of the results or carry-over between samples. The method shows no interference from carbamylated haemoglobin, and recognises the presence of haemoglobinopathies, which triggers the correction of the HbA1c result. Comparison with established methods showed good correlation, not only with the G7 but also with the Variant II and HA-8160 systems. Conclusions: With respect to reproducibility, chromatographic resolution, speed of analysis and identification of Hb variants, the Tosoh G8 analyser can be considered to be state of the art. Clin Chem Lab Med 2010;48:365–71.

Evaluation of a new Sebia kit for analysis of hemoglobin fractions and variants on the Capillarys system.

Abstract We evaluated the analytical performances of the new Sebia kit for quantification of hemoglobin fractions (HbA, HbF and HbA2) and structural hemoglobin variants on the Capillarys® system. This automated capillary zone electrophoresis method uses an alkaline buffer with silica capillaries and spectrophotometric detection. Specimen stability was evaluated during 1 month. The reproducibility of migration and the imprecision of quantification were also investigated. Comparison with the Beckman P/ACE® system was performed on 202 samples. A total of 131 subjects without any hematological abnormality were analyzed to establish the HbA2 reference ranges based on our local population. Quantification of the Hb fractions and variants exhibited excellent stability for 4weeks of storage at 4°C, with CVs <0.3%. The imprecision of the migration normalized to that of HbA2 for all hemoglobins tested (fractions and variants) was low, with a CV of <2.5%. At physiological and pathological levels, total imprecision ranged from 1.9% to 4.6% for HbA2, from 0.6% to 9.7% for HbF, and from 0.6% to 1% for HbS. Statistical analysis revealed a small proportional negative bias for HbA2 (−8.6%). Small systematic bias (−0.2%) and proportional bias (−28%) were observed for HbF. No statistically significant difference was found for HbS. The reference range for HbA2 was 2.1–3.2%. The Capillarys® system is a fully automated and accurate system that gives high-resolution performance and displays appropriate characteristics for use as a routine method for the diagnosis of thalassemias and hemoglobinopathies.

Two-site automated chemiluminescent assay for measurement of immunoreactive renin

Measurement of renin is important for the clinical assessment of hypertensive patients and for the screening for primary aldosteronism. The aim of this study was to evaluate the performances of an automated immunoassay for measurement of immunoreactive renin. Functional sensitivity, in vitro stability, and reference values were determined. Method comparison with the plasma renin activity assay was also performed. Our results demonstrate that the Liaison® direct renin assay may assist the clinician in the assessment of hypertensive patients and in the screening for primary aldosteronism.

Cross-reactivity of insulin analogs with the Diasorin Liaison insulin assay.

Insulin or insulin secretagogue treatment of diabetes mellitus remains the most common cause of hypoglycemia (1). The measurement of circulating concentrations of insulin is therefore part of the workup and management of hypoglycemic disorders, as recently indicated by the clinical practice guideline of the Endocrine Society (1). The awareness about the specific detection abilities of an insulin assay for insulin and insulin analogs is mandatory for the evaluation of potential factitious insulin-induced hypoglycemia. Previous reports have already determined the cross-reactivities to insulin analogs of some automated insulin assays (2–4). Such data have not yet been published for the Liaison insulin automated immunoassay. The aim of our study was therefore to evaluate the crossreactivity of the Liaison insulin assay (Diasorin, Saluggia, Italy) with some insulin analogs currently used for the treatment of diabetic patients. The Liaison insulin assay format is an immunometric assays using monoclonal antibodies with a chemiluminescence based method and is calibrated using the international reference standard NIBSC 66/304. The observed coefficients of variation for this assay in our laboratory are 25.4%, 5.3% and 9.1% at 0.7, 15 and 22 mUI/mL, respectively. The evaluation of cross-reactivity was performed with three different recombinant insulin analogs: lispro (Humalog ; Eli Lilly and Company), aspart (NovoRapid 300 FlexPen ; Novo Nordisk Pharmaceuticals), and glargine (Lantus ; Aventis Pharmaceuticals). The insulin analogs having a concentration of 100 kIU/L were diluted with a 10 g/L bovine serum albumin solution (BSA; Sigma Aldrich, St. Louis, MO, USA) or with insulin depleted serum (Sunnylab, Sittingbourne, UK) to reach final insulin concentra-

Clauss assay and fibrinogen protein estimated by capillary zone electrophoresis

Abstract Background: The clottability and the amount of total protein in fibrinogen provide information about qualitative or quantitative alterations. We aimed to evaluate whether capillary zone electrophoresis (CZE) Capillarys II analyzer with the protein 6 buffer is able to estimate the amount of fibrinogen antigen. Methods: Citrated plasmas were assayed for clottable fibrinogen, and any relationship with the β2-globulin fraction (percentage of the area under the curve) was evaluated. The integration method used was “tangent skimming” in order to reduce the overestimation due to high protein background. Linearity was optimized according to the ICH Q2R1 recommendations and evaluated using polynomial regression. The precision was computed in accordance with the Clinical and Laboratory Standards Institute EP5-A2 protocol. In patients, clottable fibrinogen (Clauss method) was compared to its protein CZE amount by Passing and Bablok regression and the Bland-Altman plot. Results: The correlation was linear y=0.0744+0.8991x (R2=0.9707) within the range of 2.26–17.26 μmol/L. The repeatability and the within-device precision were <15% for three levels of percentage of the β2-globulin fraction (1.61%, 3.51%, and 9.24%). In patients, clottable fibrinogen and its protein amount were similar (–0.1779+0.9654x). The ratio activity/protein was 1.08±0.32 (mean±2 SD). Conclusions: CZE with the Capillarys II and the buffer protein 6 is an easy method. It is a good candidate for estimation of the concentration of fibrinogen antigen, which may have diagnostic utility for the screening of quantitative or qualitative fibrinogen abnormalities.