Comparison of performance of classical clinical chemistry analysers with test-strip devices (Reflotron) and those based on film technology (Vitros) in external quality assessment (EQA) surveys.
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This article reports on the performance of two "dry" chemistry devices, (Reflotron, Roche Diagnostics and Vitros, Johnson & Johnson) and compared them with classical "wet" chemistry analysers in four commercially produced quality assessment samples (Roche PNU and PPU and Seronorm Human and Human High Controls) sent repeatedly over a 12-month observation period. Eleven analytes (including five enzymes) were studied, eight of which had target values set by reference method procedures. The results showed that both devices gave comparative results for the same sample sent in different EQA-surveys. Statistically significant differences which occurred were due to the high precision of measurement with a minimal shift in the measured concentrations. They had no clinical relevance in interpretation of results. Comparisons between "dry" and "wet" chemistry results for the same analyte were almost always statistically significantly different and often large enough to influence the clinical interpretation of results. Examples here were glucose and uric acid measured with the Reflotron and compared with other Roche devices (Cobas, Hitachi). The Vitros showed deviant values for urea and creatinine, when compared with other measuring devices using liquid reagents. Differences seen were constant over time, but must be seen in context with the matrices of the samples sent. The results show the long term stability of both reagents and test kits, a necessary prerequisite for long-term controlling of precision and indirectly accuracy of patient measurements.Keywords:
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We tested the accuracy of the Reflotron System by comparing results given by this system for estimations of glucose, SGOT, SGPT, cholesterol and triglycerides on patients samples which were already analysed on either an autoanalyser HITACHI 705 or manually on CLIN ICON 4010. Reflotron estimations correlated well with both Hitachi and Clinicon estimations and the strips gave reproducible results. We for small laboratories in our expanding rural health conclude that this or similar systems will be ideal services (JPMA 38: 205, 1988).
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We evaluated analytical and performance quality of the new oxidation methods for direct and total bilirubin on the Abbott Aeroset clinical chemistry analyzer. Within-day imprecisions for Abbott Aeroset assays ranged from 0.7 to 2.9% and between-day imprecisions from 2.1 to 7.3%. Inaccuracies as compared with the control "target values" for the Jendrassik-Gróf method showed deviations of -18.2 to +4.2%. Limits of detection were determined and showed very low values of < or = 0.25 micromol/l and dilution linearities were confirmed up to > 300 micromol/l. A method comparison for 100 patient samples with established Jendrassik-Gróf and DPD methods on the Roche Hitachi 717 showed good linearities between the investigated methods (r > or = 0.995). Due to slopes that ranged from 0.829 to 0.950, reference ranges for the oxidation methods differ slightly from those of established Roche Jendrassik-Gróf methods, but results can be adapted by the introduction of converting factors. In conclusion, the oxidation bilirubin assays revealed convincing analytical and performance qualities for medical needs that were similar or even better than for established methods. Application of the oxidation methods on the Aeroset clinical chemistry analyzer also improves laboratory efficiency by increasing throughput, speed of obtaining results and lowered sample and reagent volumes compared to established methods.
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The aim of our study was to perform verification of serum indices on three clinical chemistry platforms.This study was done on three analyzers: Abbott Architect c8000, Beckman Coulter AU5800 (BC) and Roche Cobas 6000 c501. The following analytical specifications were verified: precision (two patient samples), accuracy (sample with the highest concentration of interferent was serially diluted and measured values compared to theoretical values), comparability (120 patients samples) and cross reactivity (samples with increasing concentrations of interferent were divided in two aliquots and remaining interferents were added in each aliquot. Measurements were done before and after adding interferents).Best results for precision were obtained for the H index (0.72%-2.08%). Accuracy for the H index was acceptable for Cobas and BC, while on Architect, deviations in the high concentration range were observed (y=0.02 [0.01-0.07]+1.07 [1.06-1.08]x). All three analyzers showed acceptable results in evaluating accuracy of L index and unacceptable results for I index. The H index was comparable between BC and both, Architect (Cohen's κ [95% CI]=0.795 [0.692-0.898]) and Roche (Cohen's κ [95% CI]=0.825 [0.729-0.922]), while Roche and Architect were not comparable. The I index was not comparable between all analyzer combinations, while the L index was only comparable between Abbott and BC. Cross reactivity analysis mostly showed that serum indices measurement is affected when a combination of interferences is present.There is heterogeneity between analyzers in the hemolysis, icteria, lipemia (HIL) quality performance. Verification of serum indices in routine work is necessary to establish analytical specifications.
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Objective To investigate the consistency and the method of correction for the detection of the activity of four enzymes between automatic biochemistry analyzer Hitachi 7600 and Vitros 350.Methods Standardized reagents,quality control,and pooled patients serum were used for the analysis.High consistency of the activity of four enzymes was obtained between the system Hitachi7600 and system Vitros 350 through the correction of the results by the introduction of calibration factors.Results The results indicated that the activity of four enzymes analyzed by automatic biochemistry analyzer Hitachi 7600 and Vitros 350 showed high consistency by way of the use of standardized reagents,quality control,and pooled patients serum as well as the use of calibration factors.Conclusion Calibration factors can be used to help to keep the consistency of the results detected by automatic biochemistry analyzer Hitachi 7600 and Vitros 350.
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Abstract Background: Measurement uncertainty (MU) is a parameter associated with the result of a measurement that characterizes its dispersion. We report results for estimating MU following the application of a top-down procedure using only proficiency test data to establish uncertainty levels for various analytes. Methods: Data were obtained from 142 laboratories participating in the Beijing Center for Clinical Laboratory (BCCL) proficiency testing/external quality assessment (PT/EQA) schemes. The 24-month study included six selected PT shipments to obtain estimates for 50th percentile (median) and 90th percentile MUs and to compare those estimates to usual analytic goals. The number of laboratory participants varied for each trial. The expanded uncertainty (U) was calculated using a cover factor of k=2 for a confidence interval of 95%. All reproducibility, method and laboratory biases came from the PT/EQA data. Results: The median U (k=2) ranged from 3.2% (plasma sodium, indirect ion selective electrode) to 32.8% (triglycerides, free glycerol blanking) for clinical chemistry analyte means from participants in the same method group. Immunoassay analyte median U results ranged from 11.3% (CA125 tumor marker, Roche) to 33.8% (prostate-specific antigen [PSA], Abbott). The range for median U was 3.5% (red blood cell [RBC], Abx) to 30.3% (fibrinogen [FBG], other) for hematology and coagulation analytes. The MUs for most analytes satisfied quality requirements. Conclusions: The use of PT/EQA data, when available, provides an effective means for estimating uncertainties associated with quantitative measurements. Thus, medical laboratories can calculate their own MUs. Proficiency testing organizers can provide participants with an additional MU estimate using only EQA data, which may be updated at the end of each survey.
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Introduction: Quality control is an integral part of the analytical laboratory to obtain a precise, accurate result and also to reduce errors. Many national level laboratories utilize internal and external quality control methods for this purpose. The commercially available quality materials used for assessing daily internal quality control (IQC) is expensive, and hence in this study, an attempt was made to know the usefulness of serum sample as a quality control material.
Objective: To study IQC for urea and creatinine in Cobas 6000 analyser using serum sample.
Materials and Method: The study was conducted in the Clinical Biochemistry Laboratory, Kasturba Hospital, Manipal Academy of Higher Education, Manipal. IQC for estimation of urea and creatinine was assessed using Cobas 6000-1 and compared with Cobas 6000-2 autoanalyser. Thirty anonymised fresh serum samples and quality control material from Biorad with two level were used and compared between two analysers. Bland Altman agreement statistical analysis was applied for evaluating comparability using SPSS version 15.
Result: Quality control materials with two levels and serum samples showed good concordance for most of the urea and creatinine values, and all values were within 2SD. Mean difference for estimation of urea with serum sample was found to be 0.03 with 95% limit of agreement from-2.67 to-2.73. Mean difference for estimation of creatinine with serum sample was found to be 0.012 with 95% limit of agreement from 0.235 to-0.26.
Conclusion: Our study showed that the fresh serum samples could be used as an IQC when control materials are not available or available one is deteriorated. An important implication of the study findings is that using serum samples for IQC will appreciably lower the cost for validation of the accuracy of the autoanalysers.
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Objective To investigate the comparability of the results of 16 routine biochemical indexes detected by different biochemical analyzers.Methods With the Beckman DXC800 automatic biochemical analyzer as the reference system and the VITROS5600 automatic biochemical immune analyzer as the compared system according to the EP9-A2,guideline established by NCCLS.The 16 routine biochemical indexes were detected in serum of patients by the two instruments.The clinical acceptability of the VITROS5600 dry chemistry system was evaluated according to the judgment basis of 1/2allowable error of the external quality assessment in CLIA′88standard.Results The reference system and the compared system had better comparability.All tests showed good correlation between the two analytical systems.The biases of all tests were clinically acceptable,except for ALT,LDH,Crea,AST,Ca and TP.Conclusion The VITROS5600 dry chemical instrument could have good comparability with the Beckman DXC800 automatic biochemical analyzer.But the biases of ALT,AST,LDH,Ca and Crea and TP in the clinical comparison at multiple levels were not acceptable.It is necessary to establish the different reference ranges aiming at different methods.
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Introduction: Our aim was to: a) verify urinary test strips for urine chemistry analysis Combur10Test® M (Roche Diagnostics GmbH, Mannheim) on analyzer Cobas u411 ; b) asses the comparability of Cobas u411 and Miditron Junior II (both Roche Diagnostics, GmbH, Mannheim). Materials and Methods: Analytical verification was performed according to CLSI guideline EP12- A. Repetability was tested on 10 consecutively repeated measurements on negative control (BIORAD, Liquicheck Urinalysis Control Level 1) and in two patient samples with pathological values. Precision from day-to-day was assesed on control samples (Level 1 and 2) in duplicate for 10 days. Comparability was evaluated comparing 87 patient›s samples on analyzers Cobas U411 and Miditron Junior II. Accuracy for glucose, bilirubin and proteins was tested by comparing the results of test strips with values measured by reference method on analyzer Architect c8000 (Abbott, IL, USA). Precision was estimated by the degree of agreement of repeated measurements, accuracy by the degree of agreement with result of reference method. Comparability was expressed with kappa coefficient with 95% confidence interval. Acceptance criteria were: precision: 90% agreement of repeated measurements, pH: acceptable bias ±1 pH unit, specific gravity: acceptable bias ± 0.005 and comparability: kappa coefficient ≥0.6. MedCalc (v12.7.2.0, Ostend, Belgium) was used for statistical analysis. Results: Precision was acceptable for all parameters, except for leukocytes in one patient›s sample (agreement for only 8/10 measurements). Comparability between analyzers was satisfactory, except for bilirubin (kappa=0.370 (0.112 to 0.628)). Accuracy for bilirubin was satisfactory (agreement 10/10). The observed differences in proteins (8/10) and glucose (6/10) were not clinically significant. Conclusion: Analytical performance of Combur10Test® M on Cobas u411 analyzer are within acceptance limits. Observed bias for glucose and proteins are not clinically significant and are caused by differences in methodology. Analyzers are comparable, except for bilirubin measurement.
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Abstract To evaluate the relationship between the enzymatic Vitros assay for creatinine determination and other methods, we determined creatinine concentration in 400 heparin samples. Plasma creatinine level was successively determined on the Vitros 750 analyzer (Johnson & Johnson Co., Rochester, NY) and on the Olympus AU2700 analyzer (Olympus France, Rungis, France), using three reagents in the same assay: Olympus‐Jaffé and two enzymatic commercial kits—Crea Plus (Roche Diagnostics, Meylan, France) and Enzymatic Creatinine (Randox, Mauguio, France). Comparison of Jaffé and enzymatic measurements of plasma creatinine levels revealed a high correlation when considering all values ranged from 20–1,000 μmol/l (r > 0.99). However, for values <60 μmol/l, enzymatic reagents provided best results. Enzymatic methodology is a better clinical choice for the accurate measurement of creatinine, especially for neonates, pediatrics, and hematology units. Because analytical performance and the costs of Randox creatinine were satisfactory for our laboratory, this method, adapted on the Olympus analyzer, was chosen for routine determination of creatinine levels. According to the Valtec protocol (8), no interferences such as hemolysis, lipemia, or bilirubin were detected for Enzymatic Creatinine Randox. J. Clin. Lab. Anal. 17:235–240, 2003. © 2003 Wiley‐Liss, Inc.
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