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 .
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
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
a day, four replicates per run.
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-
D-dimer, mean, µg/L
dimer concentration is below the cut-off value, and should be clinically validated .
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
 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
given recently [11, 12].
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-
Product calibrator traceability
ing deep venous thrombosis (DVT) based on phlebography according to Rabinov , 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.
Cut-off: 500 µg/L
Negative predictive value
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
mined to be <100 ppm.
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.
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Data subject to change without notice.
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THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 278, No. 48, Issue of November 28, pp. 47987–47996, 2003 © 2003 by The American Society for Biochemistry and Molecular Biology, Inc. Printed in U.S.A. Structural Rearrangements of the 10 –23 DNAzyme to ␤3 IntegrinSubunit mRNA Induced by Cations and Their Relations to theCatalytic Activity*
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