1,720,996 research outputs found
Quality specifications for biochemical markers of myocardial injury
No full textBACKGROUND:
The current approach to the diagnosis and monitoring of myocardial damage, recognizes to biochemical markers, and in particular to troponins, a key role being well demonstrated that all elevated values were associated with a worsened prognosis. In 2001, the IFCC Committee on Standardization of Markers of Cardiac Damage published guidelines addressing the quality specifications for troponin assays in order to guarantee an analytical performance satisfying medical requirements and to standardize the quality of commercial methods. We describe how the application of quality specifications may be useful in daily practice, in order to provide advice to clinicians in the investigations of complex clinical cases of patients suffering from myocardial damage.
MATERIALS AND METHODS:
The samples from three patients (cases 1-3) admitted to the hospital with symptoms suggestive of cardiac disease, showing high troponin I (cTnI) values not correlated with clinical condition, were investigated in order to verify the accuracy of the laboratory data. The standard of quality specifications related to assay specificity, imprecision and interferences were evaluated using different platforms for cTnI assays, carrying out imprecision profile and specific studies on more common interferents in immunoassays.
RESULTS:
The obtained results allow us to demonstrate two cases of false-positive cTnI values attributable to a macrocomplex between a modified "in vivo" cTnI and immunoglobulin G (case 1) and to a presence of heterophilic antibodies affecting the RxL Dimension procedure (case 3). Instead, the accuracy of data obtained in case 2 was evidenced by the imprecision profile obtained in our laboratory and by the comparison of results between different laboratories using same platform.
CONCLUSIONS:
The lack of standardization as well as the wide differences in the development of each assay give rise to major concerns regarding cTnI determinations. The laboratory must therefore check the compliance between the analytical characteristics of the method utilised against recommended quality specifications for a reliable understanding of the frequency of false-positive results as well as other serious analytical errors
Evaluation of a new automated system for the determination of CK-MB isoforms.
No full textWe evaluated a new analyzer (Cardio REP) specifically designed for cardiac CK-MB isoenzyme and isoforms activity, with a performance time of 24 minutes. Ten AMI patients, with times elapsed between the onset of chest pain and admission to hospital ranging from 30 minutes to 4 hours, were monitored every 3-4 hours until the 16th hour of hospitalization. In each serum sample, in addition to total CK-MB and CK-MB isoforms measured by the Cardio REP analyzer, we also assayed total CK activity, CK-MB activity by immunoinhibition method, CK-MB mass concentration, CK-MB isoforms by REP method, troponin T, and myoglobin. The precision study demonstrated acceptable within assay and between assay CVs% for total CK-MB (8.1 and 10.4), MB1 (9.1 and 14.2), and MB2 (9.1 and 8.2) isoforms. The method was found to be linear up to 371 U/L for MB2 isoform fraction and up to 516 U/L for total CK-MB. Results for CK-MB obtained with the Cardio REP correlated well with those for CK-MB activity obtained with the immunoinhibition method (r = 0.869) and those of CK-MB mass concentration (r = 0.923). The sensitivity of the Cardio REP CK isoforms method was found to be greater than that of the REP CK isoforms method. Time to first increased value of MB2/MB1 ratio and MB2 isoform was earlier in comparison to that for CK-MB mass concentration and similar to that for myoglobin, a marker that, however, lacks specificity. The diagnostic efficiency of CK-MB isoforms and the availability of a real-time, fully automated method for their measurement suggest that utilization of this biochemical marker in emergency for the early diagnosis of AMI
Identification and quantification of hemoglobins in whole blood: the analytical and organizational aspects of Capillarys 2 Flex Piercing compared with agarose electrophoresis and HPLC methods.
No full textAbstract
BACKGROUND:
The present study was conducted to evaluate the analytical performance and the organizational aspects of Capillarys 2 Flex Piercing system (CFP) respect to agarose electrophoresis and HPLC methods in hemoglobinopathies screening.
METHODS:
The measurement of imprecision in HbA 2 and HbF quantification was verified on HbA 2 CFP control and on three samples; 74 whole blood samples were used to evaluate migration time imprecision of hemoglobin variants S, C and E (HbS, HbC, and HbE); to compare methods, 451 samples were tested on CFP and HPLC; reference values were verified as value distribution in 160 blood donors and at ROC curve analysis on 449 samples from routine analysis.
RESULTS:
Imprecision: the analytical CV % s ranged from 1.25 to 3.9 at HbA 2 quantification, the CV % was 3.78 at HbF quantification; the running time imprecision for HbS and HbC and HbE ranged from 0.20 to 0.69 % . Method comparison: at regression analysis findings were HbA 2: CFP=1.21×HPLC–0.64, HbF: CFP=1.31×HPLC−0.75, HbS: CFP=1.10×HPLC−3.24. Reference values: the HbA 2 95th percentile range was 2.5–2.8; HbF was undetectable in 154 out 160 samples tested; at ROC curve analysis the best combination of sensitivity and diagnostic efficiency was obtained using 2.2 and 3.0, as reference values, for HbA 2 and 1.1 as the upper reference limit for HbF. Organizational aspects: with respect to the procedures currently implemented in our laboratory CFP requires 2 h less time and obviates the need for some manual steps.
CONCLUSIONS:
The quantification, reproducibility and diagnostic efficiency provided by CFP in identification and quantification of hemoglobins appear accurate. In addition, the use of primary tubes allows improved safety, and the avoidance of some manual steps, that prolong working time and are a source of possible errors
Heterophilic antibody interference in a non-endogenous molecule assay: an apparent elevation in the tacrolimus concentration.
No full textBACKGROUND:
In drug monitoring assays the most common interferences are due to hematocrit, other drugs or their metabolites, while the interference by heterophilic antibodies has been reported only when measuring endogenous molecules. In the present paper a heterophilic antibody interference in the tacrolimus measurement is described.
METHODS:
Samples from a patient treated with tacrolimus were analyzed on RxL Dimension analyzer. Ranging drug concentrations from 49 to 12.5 microg/L, even after the interruption of the treatment, confirmation analysis were performed using heterophilic blocking tubes before tacrolimus measurement on the same analyzer, then testing the samples on V-Twin System, finally incubating the samples with chlorophenol red beta-d-galactopyranoside, beta-galactosidase, polyclonal mouse IgG, protein A and Protein G resin.
RESULTS:
The elevated tacrolimus concentrations were due to the presence of an interference attributable to heterophilic antibodies, as confirmed by treating the samples with heterophilic blocking tubes and protein G resin.
CONCLUSIONS:
a) The interference caused by heterophilic antibodies can be found not only in immunoassays measuring endogenous molecules, but also in those for exogenous molecules; b) the pre-treatment sample procedure, which represent the main difference between the methods affected and unaffected by the interference, is a fundamental step in removing the antibodies responsible of the interference
Analytical performance of Immunotrac AIO analyzer cardiac markers on plasma and whole blood samples
No full textNew biochemical markers: from bench to bedside
No full textBackground: Evaluation of patients presenting to hospital with chest pain or other signs or symptoms suggesting acute coronary syndrome (ACS) is problematic, time-consuming and sometimes expensive, even if new biochemical markers, such as troponins, have improved the ability to detect cardiac injury. However, patients with normal troponin values are not necessarily risk-free for major cardiac events.
Methods: Recent investigations indicate that the overall patient risk may be assessed earlier than before, thanks to new knowledge acquired concerning the pathobiology of atherosclerosis and molecular events involved in the progression of disease, thus allowing the development of new biochemical markers. Some selected markers are released during the different phases of development of cardiovascular disease and may be useful for the diagnosis of patients with cardiovascular disease. In particular, the identification of emerging markers that provide relevant information on the inflammatory process, and the development of biomarkers whose circulating concentrations suggest the status of plaque instability and rupture, seems to be of particular value in prognosis and risk stratification. The overall expectations for a cardiovascular biochemical marker are not only its biological plausibility but also the availability at a reasonable cost of rapid, high quality assays, and their correct interpretation by clinicians using optimal cut-offs.
Conclusion: The crossing from bench to bedside for each new marker discovered, must be associated with concurrent advances in the characterization of analytical features and the development of routine assay, in the assessment of analytical performance and in interpretative reporting of test results as well as in the training of physicians to use the array of biomarkers available appropriately and to interpret them correctly. This approach calls for the coordinated support of clinicians, technology experts, statisticians and the industry so that new biochemical developments can be of optimal value. (c) 2007 Elsevier B.V. All rights reserved
Carboxypeptidase N and creatine kinase-MB isoforms in acute myocardial infarction.
No full texthe aims of our study were to evaluate the plasma carboxypeptidase N activity in normal subjects and in patients with acute myocardial infarction and to delineate its relationship with creatine kinase-MB isoforms in monitoring of acute myocardial infarction, carboxypeptidase N being the major determinant of creatine kinase isoform conversion in plasma. The study was carried out in 34 healthy subjects and 19 patients with acute myocardial infarction diagnosed according to the World Health Organization (WHO) criteria in which the blood samples were collected immediately upon admission to the coronary care unit (median time 3.5 hours), every 4 to 6 hours for 24 hours, and every 12 hours until the third day post admission. Carboxypeptidase N activity, total creatine kinase, creatine kinase-MB mass concentration and creatine kinase-MB isoforms were determined in each sample from acute myocardial infarction patients, whereas only carboxypeptidase N and total creatine kinase activities were assayed in samples from healthy subjects. The results showed a high variability in carboxypeptidase N values among healthy subjects (median = 200 U/l; interquartile range = 190-247 U/l) and in the first available samples from acute myocardial infarction patients (median = 213 U/l; interquartile range = 234 U/l) without significant differences between groups and without a correlation between carboxypeptidase N and creatine activities either in healthy subjects or in acute myocardial infarction patients; in the latter group, however, a significant correlation (p < 0.01) with creatine kinase-MB calculated on all samples, was observed. In acute myocardial infarction patients carboxypeptidase N showed time-related variations, reaching the highest levels about 48 h after onset of chest pain. A statistically significant difference in carboxypeptidase N values (p = 0.0001) was found before and after creatine kinase-MB peak values as well as before and after MB2/MB1 normalization. Worthy of note is the finding that in two acute myocardial infarction patients presenting MB2/MB1 ratios lower than the cutoff value (1.5) throughout the period of observation, the baseline values for carboxypeptidase N were higher than in other patients studied. Our results suggest that the increase of carboxypeptidase N activity after infarction could be induced by an increase in endogenous substrate concentrations, in particular creatine kinase-MB released from damaged myocardium. Furthermore, high baseline levels of carboxypeptidase N will reduce the diagnosis efficiency of creatine kinase-MB isoforms in the diagnosis of acute myocardial infarction
Fluoroenzymometric method to measure cardiac troponin I in sera of patients with myocardial infarction.
No full textThe aim of our study was to evaluate the clinical relevance of serum troponin I (TnI) as a marker of ischemic myocardial injury by using an automated fluoroenzymometric assay. The reference range for serum TnI was established by measuring serum TnI concentrations in blood from 75 healthy donors. The concentration was then compared with serum creatine kinase (CK) activity, CK-MB mass, and myoglobin concentrations in 20 patients with myocardial infarction diagnosed according to the WHO criteria, 20 patients with chest pain of nonischemic origin, 9 patients with unstable angina, 11 with stable angina, 11 patients with chronic muscular diseases, 6 patients with muscular trauma without chest contusion, and 13 patients with chronic renal disease. We found that: (a) 99% of the blood donors had TnI concentrations 96 h); (d) receiver-operating characteristic curve analysis showed the high diagnostic accuracy of TnI in diagnosing AMI even in patients in whom traditional biochemical markers are adversely influenced by underlying clinical situations
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