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AQT90 FLEX analyzerClinical sheet D-dimer Intended use The D-dimer test is intended as an aid in the diagnosis of venous thromboembolism (deep vein thrombosis and pulmonary embolism).
SummaryUnder normal physiological conditions, the hemostatic system maintains the balance between two opposing processes: • The coagulation process leads to the formation of thrombin, which converts fibrinogen to fibrin monomer molecules, with release of fibrinopeptides A and B. These fibrin monomer molecules polymerize forming an insoluble fibrin network stabilized by covalent cross-links introduced by the action of the enzyme factor XIIIa, causing the formation of a thrombus. • The fibrinolytic process leads to the lysis of the cross-linked fibrin by plasmin into a heterogeneous population of fragments released into the blood. These end-stage fibrin degradation products are called D-dimer [1].
Under pathological conditions, a thrombus may escape the normal fibrinolytic system to grow and propa-gate. As D-dimer is a specific marker of the breakdown of a fibrin clot and an indirect marker of fibrin formation, its measurement may reflect a disturbance in this hemostatic balance. Indeed, D-dimer levels increase one hour after thrombus and have a half-life of 4 to 6 hours. The AQT90 FLEX assay combines high negative predictive value with very high specificity.
Diagnostic performance for the detection of proximal DVT T9 AQT90 FLEX
AQAQT90 FLEX
Therefore, the presence of D-dimer can be used as an early sensitive marker for thrombotic disorders such as deep vein thrombosis (DVT), pulmonary embolism (PE), disseminated intravascular coagulation (DIC) and for Within-day and total imprecision were determined by analyzing spiked plasma pools over 20 days, two runs coronary artery diseases. However, as high levels of D-dimer are observed in a wide variety of conditions (for example, pregnancy, post-surgery state, in malignancy, trauma, cancer), it is not a specific marker.
The result of the D-dimer assay is used as an aid in ruling out the suspicion of DVT or PE [2, 3, 4], when D- dimer concentration is below the cut-off value, and should be clinically validated [11].
The clinical usefulness of a D-dimer assay is demonstrated by the decrease in the number of invasive and expensive investigations required to diagnose a condition. D-dimer assay can also be helpful in detecting DIC [5] and is a potential addition to clinical diagnosis models for the risk stratification of patients with ischemic heart disease [6, 7, 8, 9, 10]. Updated recommendations regarding the clinical use of D-dimer have been Clinical performance of the AQT90 FLEX D-dimer assay was evaluated analyzing a clinically characterized panel consisting of citrate specimens of 170 patients. Of this patient population, 64 were diagnosed as hav- ing deep venous thrombosis (DVT) based on phlebography according to Rabinov [15], performed without The D-dimer assay is calibrated with HyTest 8D70 material. compression during injection of at least 100 mL iodine 240 mg/mL. The leg that was examined was not weight bearing.
DVT restricted to the calf veins was classified as distal, whereas DVT in the popliteal, femoral, iliac or inferior Blood samples are collected by venipuncture. Whole-blood samples with either citrate, EDTA or lithium caval veins was classified as proximal.
heparin as anticoagulant can be used.
Analytical specificity
The analytical specificity of the AQT90 FLEX D-dimer assay was determined by studying the cross-reactivity with fragment D and fragment E at concentrations of 40,000 μg/L and 20,000 μg/L respectively. The cross These values should only be used as examples, and each laboratory should establish its own diagnostic cut- reactivity of fragment D was estimated to be 3 % for patients with no fragment D elevations. For highly off values for venous thromboembolism.
elevated fragment D levels the cross-reactivity was up to 28 %. Fragment E showed no cross-reactivity.
The study was performed in cooperation with the University Hospital of Southern Denmark in Esbjerg, Analytical sensitivity and measuring range
The limit of detection has been determined to be 35 μg/L. The reportable range of the assay is 80-100,000 μg/L. Hook effectNo hook effect was observed for concentrations up to 220,000 μg/L.
Reference valuesWhole blood (lithium-heparin, EDTA and citrate) samples was obtained from 272 apparently healthy indi- viduals (54 men and 78 women < 50 years of age; 74 men and 66 women > 50 years of age) and analyzed Carry over from a sample with D-dimer value (297,726 μg/L) to an adjacent negative sample was deter- using the AQT90 FLEX D-dimer assay. The 95th percentile was determined to be 583 μg/L for persons < 50 years of age and 654 μg/L for persons > 50 years of age. NOTICE: These values should only be used as examples. Each laboratory should establish its own reference Haemolytic, lipaemic and icteric samples do not interfere with the assay.
Fibrinogen and immunoglobulin G, at concentrations of 8,000,000 μg/L and 16,000,000 μg/L respectively, were also tested. There was no interference of cross-reactivity from either fibrinogen or immunoglobulin G.
The following interfering substances were found to have no notable effect on the AQT90 FLEX D-dimer as-say (interference < 20 %). The interference was tested by using a plasma pool with 465 μg/L of D-dimer and spiked with the interfering substance at the following concentration (about 5 times the upper therapeutic range): Abciximab, Acetaminophen, Acetylsalicylic acid, Allopurinol, Ambroxol, Ampicillin, Ascorbic acid, Atenolol, Caffeine, Captopril, Cefoxitin, Cinnarizine, Cocaine, Diclofenac, Digoxin, Dopamine, Erythromycin, Ethanol, Heparin low molecular weight, Heparin Sodium, Ibuprofen, Levodopa, Methyldopa, Metronidazole, Nicotine (±),Nifedipine, Nitrofurantoin, Nitroglycerin, Nystatin, Oxytetracycline, Phenylbutazone, Phenytoin, Propranolol, Quinidine, Rifampicin, Tetracycline, Theophylline, Trimethoprim, Verapamil, Warfarin.
References1. Houdijk WPM. The laboratory determination of D-dimer. Dev Thromb Hemost 1999; 2: 1-13.
2. Kelly J, Hunt BJ. Role of D-dimers in diagnosis of venous thromboembolism. The Lancet 2002; 359: 456-57.
3. Tovey C, Wyatt S. Diagnosis, investigation, and management of deep vein thrombosis. BMJ 2003; 326: 1181-84.
4. Bounameux H, De Moerloose P, Perrier A, Miron MJ. D-dimer testing in suspected venous thromboembolism: an update. Q J Med 1997; 5. Taylor FB Jr, Kinasewitz GT. The diagnosis and management of disseminated intravascular coagulation. Curr Hematol Rep 2002; 1,1: 6. Kruskal JB, Commerford PJ, Franks JJ, Kirsch RE. Fibrin and fibrinogen-related antigens in patients with stable and unstable coronary artery disease. N Engl J 1987; Med 317: 1361-65.
7. De Maat MP, Bladbjerg EM, Drivsholm T, Borch-Johnsen K, Moller L, Jespersen J. Inflammation, thrombosis and atherosclerosis: results of the Glostrup study. J Thromb Haemost 2003; 1,5: 950-57.
8. Menown IB, Mathew TP, Gracey HM et al. Prediction of recurrent events by D-dimer and inflammatory markers in patients with normal cardiac troponin I (PREDICT) study. Am Heart J 2003; 145,6: 941-42.
9. Tataru MC, Heinrich J, Junker R et al. D-dimers in relation to the severity of atherosclerosis in patients with stable angina pectoris after myocardial infarction. Eur Heart J 1999; 20,20: 1493-502.
10. Bayes-Genis A, Matao J, Santàlo M et al. D-Dimer is an early diagnosis marker of coronary ischemia in patients with chest pain. Am 11. Burnett B, Harmon K, Key N, McBane R, Miley T. Technology assessment report: D-dimer testing for deep vein thrombosis and pulmo- nary embolism. Institute for Clinical Systems Improvements, USA 2003.
12. American College of Emergency Physicians, Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected pulmonary embolism. Ann Emerg Med 2003; 41: 257-70.
13. Lövgren T and Pettersson K (1990). Time-resolved fluoroimmunoassay, advantages and limitations. In Luminescence Immunoassay and Molecular Applications, K Van Dyke and R Van Dyke, eds. Boca Raton, USA, CRC Press, 233-53.
14. Lövgren T, Meriö L, Mitrunen K, et al (1996). One-step all-in-one dry reagent immunoassays with fluorescent europium chelate label and time-resolved fluorometry. Clin Chem 42, 1196-201. 15. Rabinov K, Paulin S. Roentgen diagnosis of venous thrombosis in the leg. Arch Surg 1972;104:134-144.
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