Correlation between sodium, potassium, hemoglobin, hematocrit, and glucose values as measured by a laboratory autoanalyzer and a blood gas analyzer.

INTRODUCTION: Blood gas analyzers can be alternatives to laboratory autoanalyzers for obtaining test results in just a few minutes. We aimed to find out whether the results from blood gas analyzers are reliable when compared to results of core laboratory autoanalyzers. MATERIALS AND METHODS: This retrospective, single-centered study examined the electronic records of patients admitted to the emergency department of a tertiary care teaching hospital between May 2014 and December 2017. Excluded from the study were patients under 18 years old, those lacking data, those who had any treatment before the laboratory tests, those whose venous gas results were reported more than 30 minutes after the blood sample was taken and for whom any of the laboratory tests were performed at a different time, and recurrent laboratory results from a single patient. RESULTS: Laboratory results were analyzed from a total of 31,060 patients. The correlation coefficients for sodium, potassium, hemoglobin, hematocrit, and glucose levels measured by a blood gas analyzer and a laboratory autoanalyzer were 0.725, 0.593, 0.982, 0.958, and 0.984, respectively; however, there were no good, acceptable agreement limits for any of the parameters. In addition, these results did not change according to the different pH stages (acidosis, normal pH and alkalosis). CONCLUSION: The two types of measurements showed a moderate correlation for sodium and potassium levels and a strong correlation for glucose, hemoglobin, and hematocrit levels, but none of the levels had acceptable agreement limits. Clinicians should be aware of the limitations of blood gas analyzer results.

[Development and analytical validation according COFRAC recommendations of pyruvate and ketone body assay on open automated analyser]. / Mise au point et validation en portée B selon les recommandations du Cofrac d'un dosage de pyruvate et de corps cétoniques sur un automate ouvert.

Measurements of pyruvate and ketones bodies (acetoacetate and 3-hydroxybutyrate) are essential to the investigation of intermediary metabolism. Indeed, their blood levels reflect energy balance influenced by nutritional status. This balance can be disturbed in certain diseases such as diabetes and some inherited metabolic disorders. We have developed methods for assays on open automated biochemistry analyser, Konelab 20 XT (ThermoFischer, Whaltham USA), using kits marketed by Sobioda (Montbonnot, France) for pyruvate and Wako Chemicals GmbH (Neuss, Germany) for ketones, on deproteinised blood sample. We have validated the performance of these three quantitative methods using NF EN ISO 15189 (range B) standard criteria. We obtain satisfactory results concerning fidelity (precision measured as within and between batch CVs are respectively less than 7% and less than 6%), measuring ranges (from 7.7 to 228 µmol/L for pyruvate and from 22.6 to 650 µM for total ketone bodies), accuracy (10.4 µmol/L in physiological range for pyruvate and 7.1 µmol/L for 3-hydroxybutyrate) and comparing methods (versus manual assay with spectrophotometry on Uvikon XL). Establishment of reference ranges (35 to 74 µmol/L for pyruvate, less than 100 µM for 3-hydroxybutyrate and less than 44 µmol/L for acetoacetate) and reagents stability study (up to 12 weeks if frozen) have enabled us to finalize method validation and to add these assays to our routine laboratory repertoire.

An automated analyzer provides clinically concordant results to manual back titration for quantitation of bicarbonate in pancreatic juice.

OBJECTIVES: Secretin pancreatic function tests play an important role in the diagnosis of chronic pancreatitis. Back titration is the standard method for measurement of bicarbonate in pancreatic juice but is time consuming and manually performed. Use of an autoanalyzer for this purpose is not validated. METHODS: Bicarbonate concentrations in secretin-stimulated pancreatic juice specimens were quantitated by manual back titration, a clinical chemistry autoanalyzer (automated bicarbonate, Roche Cobas c501, Roche Diagnostics, Indianapolis, Ind), and a blood gas analyzer (calculated bicarbonate, GEM 3000, Instrumentation Laboratories, Bedford, Mass). Kappa statistic analysis, Bland-Altman analysis, and Lin concordance correlation coefficients were calculated. RESULTS: Ninety specimens from 31 subjects were included. Using a bicarbonate concentration of 80 mEq/L as a cutoff value, there was poor agreement between back titration and calculated bicarbonate (κ = 0.188); however, only 1 specimen showed discrepancy between back titration and automated bicarbonate (κ = 0.977). The limit of agreement between the back titration and automated bicarbonate was -9.0 to + 8.3 mEq/L. The Lin concordance correlation coefficient between the 2 methods was 0.931 (P < 0.001). CONCLUSIONS: There is strong concordance between manual back titration and chemistry autoanalyzer methods for measurement of bicarbonate concentrations in pancreatic juice. Autoanalyzers may replace back titration for this purpose. Blood gas analyzers are unsuitable.

Garrison’s model of self-directed learning: preliminary validation and relationship to academic achievement

In this project, 119 undergraduates responded to a questionnaire tapping three psychological constructs implicated in Garrison’s model of self-directed learning: self-management, self-monitoring, and motivation. Mediation analyses showed that these psychological constructs are interrelated and that motivation mediates the relationship between self-management and self-monitoring. Path modeling analyses revealed that self-management and self-monitoring significantly predicted academic achievement over two semesters with self-management being the strongest predictor. Motivation significantly predicted academic achievement over the second semester only. Implications of these findings for self-directed learning and academic achievement in a traditional classroom setting are discussed (AU)

En este trabajo, 119 estudiantes posgraduados fueron evaluados de acuerdo con un cuestionario que mide tres constructos psicológicos implicados en el modelo de Garrison sobre aprendizaje autodirigido: autogestión, autoseguimiento, y motivación. Los análisis de mediación mostraron que estos constructos psicológicos están interrelacionados y que la motivación media en la relación entre autogestión y autoseguimiento. Los análisis de Path modeling indicaron que la autogestión y el autoseguimiento predecían significativamente el logro académico a lo largo de dos semestres en los que la autogestión era el mejor indicador. La motivación predecía significativamente el éxito académico sólo a lo largo del segundo semestre. Se discuten las implicaciones que estos resultados pueden tener sobre el aprendizaje autodirigido y el éxito académico en el contexto de un aula tradicional (AU)

Valoración de la automedida de la presión arterial en el diagnóstico de la hipertensión clínica aislada. Estudio VAMPAHICA / Appraisal of self-measurement of blood pressure in the diagnosis of isolated clinical hypertension. VAMPAHICA study

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Performance characteristics of four automated natriuretic peptide assays.

Measurement of circulating B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) can identify patients with heart failure and guide therapy. The limit of detection, linearity, imprecision, method comparison, analytic concordance, and reference intervals of the Access 2 BNP (Biosite, San Diego, CA), ADVIA Centaur BNP (Bayer Diagnostics, Tarrytown, NY), AxSYM BNP (Abbott Diagnostics, Abbott Park, IL), and E170 NT-proBNP (Roche Diagnostics, Indianapolis, IN) methods were evaluated. The Triage meter BNP assay (Biosite) was the comparison method. Imprecision testing showed total coefficients of variation of 4.1%, 4.4%, 5.5%, and 0.8% for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. Relative to the Triage meter, method comparison revealed a slope of 0.96 and r = 0.95, a slope of 0.77 and r = 0.92, a slope of 1.13 and r = 0.94, and a slope of 8.8 and r = 0.80 for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. Overall analytic concordance values with the Triage meter were 95.9%, 92.9%, 92.4%, and 84.3% for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. All automated natriuretic peptide methods showed acceptable analytic performance.

Implications of autoverification for the clinical laboratory.

In an era of financial stress, the clinical laboratory must maximize the efficiency of its operations. In this context, Centralized Laboratory Services, Inc., Long Island City, New York, attempted to introduce autoverification into its chemistry department. We discuss some of the issues associated with implementation of autoverification and also our effort to get an approximate quantitative estimate of the extent of productivity improvement related to the initiation of autoverification at Centralized Laboratory Services (CLS). We used payroll and expense records for 4-week periods preceding and following the introduction of autoverification to construct such an estimate. On an annualized basis, CLS data suggests a maximum savings of approximately 0.3 FTEs from the introduction of autoverification. This represents 3.1% of the workforce in the chemistry department at CLS.

Selection of an optimal combination of decision criteria for the internal quality control in an automatic analyzer.

After some years using an automatic analyser model Hitachi 705, we faced the task of selecting a reasonable combination of statistical procedures for internal quality control in order to use it in a computer program, by means of which, one could apply all the decision criteria in a rapid and automatic manner. As a result of the first 3 years of work, an algorithm was adopted that includes the multirule procedure originally proposed by Westgard, but with three main differences: (1) All the control rules are always applied; (2) the 4(1S) and 10x control rules are used as criteria for warning or caution but not for run rejection; and (3) the control limits are recalculated daily using all the accumulated control results (just the accepted values). The 2(2S), 4(1S) and 10x rules are applied first across materials (considering consecutive observations in different control materials), and then within materials (for consecutive observations on the same control material). The program not only has permitted us to improve our capacity for error detection, but it has also permitted the reduction of run rejections making an important decrease in costs possible and a significant improvement in quality.

Determination of 18 beta-glycyrrhetinic acid in human serum using the fully automated ALCA-system.

We report a method for the determination of 18 beta-glycyrrhetinic acid (glycyrrhetinic acid) in human serum using the ALCA-system. The technology of the ALCA-system is based on the principles of adsorptive and desorptive processes between liquid and solid phases. The assay is run fully automated and selective. Procedural losses throughout the analysis are negligible, thereby allowing for external calibration. The calibration curve is linear up to 10 mg/l and concentrations as low as 10 micrograms/l are detectable. CV is 2.5% for within- and 7.5% for between-assay precision at a level of 50 micrograms/l and 1.2% for within- and 8.5% for between-assay precision at a level of 500 micrograms/l. Specific and expensive reagents are not necessary and time-consuming manual operations are not involved. This assay can be selected from a wide spectrum of methods at any time. Thus, the present method is well-suited for drug monitoring purposes in the routine laboratory. In a pharmacokinetic study we measured serum levels of glycyrrhetinic acid in ten healthy young volunteers after ingestion of 500 mg glycyrrhetinic acid. Maximum levels of glycyrrhetinic acid were 6.3 mg/l 2 to 4 hours after ingestion. Twenty-four (24) hours after ingestion seven probands still had glycyrrhetinic acid levels above the detection limit with a mean level of 0.33 mg/l.

Automation of human sperm cell analysis by flow cytometry.

Semen sample analysis is routinely performed by microscopical evaluation and manual techniques by laboratory operators; the analysis is affected by a wide imprecision related to variability among observers, influencing its clinical validity. Our aim was to automate sperm analysis with the use of flow cytometry for evaluation of cell counts and typing and with the use of a new membrane-permeant nucleic acid stain for evaluation of sperm viability. Statistical analysis of the comparison between manual and automated methods for sperm counts was performed by the Bland and Altman method; the mean difference was 0.243 x 10(6) sperms/ mL. The precision of the flow cytometric analysis was evaluated with whole sperm; the between-run CV was 7.5% and the within-run CV was 2.5%. Data observed suggest that flow cytometric sperm analysis, with high precision and accuracy and low costs, can be proposed for routine use in clinical laboratories.

Performance evaluation of automated immunoassays on the Technicon Immuno 1 system.

We performed an immunoassay evaluation for various analytes on a fully automated random-access analyzer, the Technicon Immuno 1 system from Bayer Corp. This system involves latex agglutination, magnetic separation sandwich, and magnetic separation competitive immunoassay configurations. The evaluated analytes were thyrotropin (TSH), triiodothyronine, thyroxine, free thyroxine, follitropin, lutropin, prolactin, beta subunit of human chorionic gonadotropin, cortisol, ferritin, alpha-fetoprotein, carcinoembryonic antigen, and prostate-specific antigen. We tested the assay precision, linearity, and correlation with comparison methods for these analytes. The functional sensitivity of the TSH assay and the sample-to-sample carryover were also studied. Excellent results were obtained for within-run and between-day precision studies, with most assays showing within-run CVs <4% and between-day CVs <6%. The linearity for all assays was acceptable and the correlation between Immuno 1 assays and comparison methods showed satisfactory results. The functional sensitivity of the TSH assay was estimated at 0.04 mU/L. No sample-to-sample carryover was detected.

Automated assay of plasma bromide after a single deproteinization step.

This study aimed to simplify the spectrophotometric fluorescein method for measuring plasma bromide, improve its reproducibility, and automate it. After major modifications of the method, we obtained an essentially linear calibration curve for plasma concentrations of bromide between 0 and 5.0 mmol/L. The intraassay CV for measuring bromide in the supernatants of deproteinized plasma samples (initial plasma concentrations 2.5-5.0 mmol/L) was as low as 0.5-1.0% (n = 9). When all the procedures were incorporated, including deproteinization and dilution of plasma, the intraassay CV was 2% at 2.5 mmol/L (n = 5) and 1% at 5.0 mmol/L (n = 5). The interassay CV for measuring bromide in plasma supernatants (initial plasma bromide concentration > 2.5 mmol/L) was 1%. Analytical recovery of bromide added to plasma was 99.1% +/- 2.5%. The new method is simpler and more reproducible than other spectrophotometric methods. Conditions for its automation are described.

Validation protocol of analytical hemostasis systems: measurement of anti-Xa activity of low-molecular-weight heparins.

A standard validation protocol adapted to the chromogenic assay of anti-Xa activity of low-molecular-weight heparins was used in a multicenter study to assess its suitability for comparing and evaluating analytical hemostasis systems. The protocol included: familiarization with the system (repeatability); assessment of limits of linearity, detection limits, and cross-contamination; and validation (reproducibility and accuracy of measurements of treated patients' plasmas). We calibrated the systems with the same range of lyophilized plasmas daily and evaluated repeatability and reproducibility by using a single batch of lyophilized plasmas at three anti-Xa activities. The two automated systems tested [SB 300 (Gilford) and ACL (IL)] and the two semiautomated systems [ST 888 (D. Stago) and Chromotimer (Behring)] gave similar mean values. Dispersion of results was lower with the automated systems than with the semiautomated ones, especially at low anti-Xa activities, a tendency that also was observed for reproducibility. Because each analytical system gave linear results for activities as great as 1000 IU/L, suitable sample dilution is advisable for higher anti-Xa activities. Accuracy was greater in the automated systems. We conclude that this protocol is feasible and is applicable to validation of other analytical hemostasis instruments, in particular the latest generation of fully automated instruments.

Use of precision profiles to evaluate precision of the automated leukocyte differential.

The commonly used methods of assessing the precision of the automated leukocyte differential have certain drawbacks that affect the validity and comparability of results. In the present report, we introduce a procedure based on building precision profiles from a large number of within-run imprecision experiments. The profiles are fitted to the function for the CV of proportions, which yields the number of theoretically differentiated leukocytes. Differences between fitted curves are evaluated for statistical significance by the F-test. As an example, we compared the precision of two hematology analyzers, a flow-cytometric technique involving fluorescence-labeled monoclonal antibodies, and the manual differential. We were able to establish definite differences in precision between different analyzers and different leukocyte classes. Our data also indicated that conventional within-run imprecision studies may completely misjudge analyzer precision. Furthermore, we could demonstrate that the precision of analyzers that analyze a fixed amount of blood rather than a fixed number of leukocytes is strongly influenced by the leukocyte count of the sample, leading to high imprecision for leukopenic samples. We believe the proposed procedure is a useful addition to currently used protocols; it yields clear results and creates a statistical basis of comparison between various instruments and techniques of differentiation.

Interlaboratory variability of bilirubin measurements.

During an 8-month study, 14 laboratories used automated analytical systems to measure total bilirubin concentrations in lyophilized bovine specimens containing 38, 169, and 253 micromol/L bilirubin (2.2, 9.9, and 14.8 mg/dL, respectively). The measured mean +/- SD (n, range) were: 39 +/- 7 micromol/L (n = 90, 31-53) [2.3 +/- 0.4 mg/dL (1.8-3.1)]; 176 +/- 29 micromol/L (n = 89, 146-222) [10.3 +/- 1.7 mg/dL (8.5-13.0)]; and 260 +/- 43 micromol/L (n = 103, 208-316) [15.2 +/- 2.5 mg/dL (12.1-18.5)]. In comparison with target values, measurements were consistently lower at 4, higher at 6, and within +/- 4% at 4 laboratories for each of the three concentrations. The measured values for each concentration remained fairly constant during the study at each laboratory. We conclude that bilirubin measurements differed significantly from the established target values at most of the participating laboratories.

Clinical comparison of three labeled-antibody immunoassays of free triiodothyronine.

Three labeled-antibody immunoassays of free triiodothyronine (FT3) were studied in hyperthyroid patients, patients with nonthyroidal illness, and patients being treated with amiodarone; we also studied sera presenting known interferences (n for all groups = 465). The results were compared with those of a one-step labeled-analog assay. The precision of the two automated assays were similar to that of the manual assays. The three labeled-antibody FT3 assays demonstrated a satisfactory diagnostic performance for confirming hyperthyroidism and robustness to interference; nevertheless, two assays displayed unusual behavior in some patients with nonthyroidal illness, with chronic renal failure, or after amiodarone therapy.

[The amino acid composition of the antigenic structures of the human heart conduction system]. / Aminokislotnyi sostav antigennykh struktur provodiashchei sistemy serdtsa cheloveka.

Amino acid composition of proteins from antigen preparations of the human heart conduction system has been studied. Differences in amino acid composition and relative affinity of the structure of two groups were found: between the sinus and atrioventricular nodes, the His bundle and contractile myocardium.

[Automated blood cell measurements: a comparison between the Bayer H2 and the Abbott Cell-Dyn 3500]. / L'esame emocromocitometrico in automazione: confronto tra Bayer H2 e Abbott Cell-Dyn 3500.

INTRODUCTION: We have compared two hematologic analyzers, H2 (Bayer) and CELL DYN 3500 (Abbott). The protocol we used was able to evaluate the overall analytical quality, the effect of aging of the sample on the measured parameters, the quality of leucocytes differential count. Number and quality of information supplied for each sample by both analyzers were then taken in account. RESULTS: Excellent correlation for all measured parameters was found: only monocytes were, albeit modestly, overestimated by CELL DYN 3500 compared to H2. Ageing of sample and temperature of storage had a marked effect on CELL DYN's measurements, resulting in impaired recognition and classification of leucocytes, while the results for the other parameters were acceptable. Comparative evaluation of the differential count of leucocytes was made between the results of both analyzers and microscopic examination. While specificity, predictive value of negative results and quantity of false negative results were practically the same, sensitivity, predictive value of positive results and quantity of false positive results were better for H2 as compared to CELL DYN (87.1% vs 78.1%, 79.4% vs 65.8, 7 vs 13, respectively). The clinical utility of supplementary informations (alarms, flags, cytograms, etc.) yielded by the analyzers was relevant for H2 regarding the erythrocytes cytograms, for CELL-DYN 3500 regarding the application of the extended lyse program for lytic resistant RBCs and of the Vet Package. CONCLUSIONS: CELL DYN 3500 performance have on the whole confirmed the producer's claims, being of reliable use in the haematological screening on account of its simplicity and more than good overall analytical quality.

Glycohemoglobin assays evaluated in a large-scale quality-control survey.

We report the results of a national quality-control survey on glycohemoglobin (GHb), monitored in France by the Société Française de Biologie Clinique on behalf of the authority of the "Agence du Médicament." A sample of lyophilized hemolysate was sent to 3109 laboratories. Results were obtained from 2770 laboratories. HbA1C, HbA1, and total GHb were measured by 50%, 24%, and 26% of the participants, respectively. Of these measurements, 79% of the HbA1C results and 76% of the total GHb results, but only 48% of the HbA1 results, were within the +/- 20% limits of the indicated target values. Mean values for the hemolysate ranged from 8% to 11% for HbA1C, from 7% to 12% for HbA1, and from 11% to 13% for total GHb. The interlaboratory CVs ranged from 3% to 20%, according to method used. So, methods used for GHb assay, which are based on various principles, exhibit very different analytical performances. Nonetheless, this large-scale study indicates that some techniques can support transferability of results from laboratory to laboratory.