Chemistry: analytical and immunological testing – Composition for standardization – calibration – simulation,... – Blood serum or blood plasma standard or control
Reexamination Certificate
1998-08-10
2001-02-27
Ludlow, Jan (Department: 1743)
Chemistry: analytical and immunological testing
Composition for standardization, calibration, simulation,...
Blood serum or blood plasma standard or control
C435S013000, C436S008000, C436S069000
Reexamination Certificate
active
06194214
ABSTRACT:
The invention relates to a process for the production of plasmas for use as a control or standard in all functional clotting tests which are used for the detection of a lupus anticoagulant.
Lupus anticoagulants are immunoglobulins and belong to the acquired autoantibodies type. They are directed against phospholipids or phospholipid/protein complexes and prolong the clotting time in customary diagnostic clotting tests (see Triplett D., et al. Hematologic Pathology 1988; 2: 121-143). These immunoglobulins are to be differentiated from other autoantibodies likewise against lipids, in particular cardiolipins. Both groups are clinically assigned to the antiphospholipid syndrome (APS) which manifests itself in thromboses and an increase in birth complications (miscarriages). The pathological mechanism of the lupus anticoagulants is still unclarified for several reasons. Firstly, the specificity of the occurring antibodies and thus the mechanism of action is individually different from patient to patient. Secondly, the subclasses of the immunoglobulins (IgM, IgG, IgA) and the antibody titers vary. Thirdly, there is a paradox between the determination of the lupus anticoagulant and clinical manifestation: a prolongation of the clotting time in in vitro tests, as is caused by lupus anticoagulant, points to an increased proneness to bleeding, in vivo, however, it is manifested in an increased proneness to thromboses.
The diagnosis of a lupus anticoagulant is therefore restricted to a phenomenological, description of the behavior of a plasma sample in various clotting tests according to the recommendations of international committees (Brandt, J. T. et al., Thrombosis Haemostasis 1995; 74: 1185-1190). These tests are the activated partial thromboplastin time (APTT), the kaolin clotting time (KCT) the dilute thromboplastin time (dPT) and the Russell's viper venom time (RVVT). A prolongation of the clotting time in these tests, however, is also obtained by a factor deficiency, which is why in the so-called plasma exchange test the pathological sample is mixed with normal plasma and as a rule determined in the APTT. A factor deficiency, as a rule, is already compensated for in a substitution of 50% by mixing with the normal plasma, while in the presence of a lupus anticoagulant pathological results are still obtained. Furthermore, the phospholipid dependence is to be checked, which is carried out using the same reagents, but with different concentrations of phospholipids. Furthermore to be differentiated are autoantibodies against individual clotting factors, which are likewise not compensated for by 1+1 mixing with a normal plasma. As a rule, these factor antibodies, however, only act in one of the two pathways of the clotting system (in particular so-called Factor VIII inhibitors) and are recognized by the comparison of the various pathways, i.e. by the comparison of the abovementioned tests (APTT for the intrinsic, PT for the extrinsic pathway).
The sensitivity of the reagents of the abovementioned tests to lupus anticoagulant is very different (Messmore, H., et al., Thrombosis and Hemostasis. 1994, 20: 79-94). Furthermore, lupus anticoagulants do not produce a pathological result in all tests, which is why the use of at least two functional tests is recommended (for example the APTT and the RVVT; see Brandt, J. T. et al.,Thrombosis Haemostasis 1995; 74: 1185-1190). For comparison or exchange of data, e.g. in clinical studies, reference to a standard would therefore be useful, as well as regular checking of the test results, for example for monitoring a therapy. The use of individual plasma donors is unsuitable for the preparation of such a standard or a control for commercial use, however, because of the heterogeneity of the specificity, the low reproducibility and the poor stability of lupus anticoagulants. At present therefore, there is neither a clear determination of a lupus anticoagulant nor a reference to the quantification of a lupus anticoagulant.
The invention was therefore based on. the object of finding a process with which, in a sample, e.g. plasma, a lupus anticoagulant can be reproducibly and quantifiably simulated in such a way that this modified plasma produces pathological results comparable with the presence of a natural lupus anticoagulant in all customary functional clotting tests and is thus suitable for quantification of the action (standard) and as a control.
An essential characteristic of the lupus anticoagulant is the dependence of the clotting-prolonging property on the availability of the phospholipids. One possibility of simulating this behavior was described by Babcock and McGlasson (U.S. Pat. No. 4,877,741). They use an extract from a spider (Loxosceles reclusa) which contains an enzyme having a sphingomyelinase D activity. They were able to show (McGlasson, D. L. et al., Am. J. Clin. Pathol 1993; 100: 576-578) that this extract in the APTT leads with various reagents to a prolongation of the clotting time and can be neutralized by addition of phospholipids. This prolongation, however, is only weakly pronounced. Thus the prolongation achieved was at most 63% of the upper standard range (APTT reagent from Pacific Hemostasis; Table 2; (McGlasson, D. L. et al., Am. J. Clin. Pathol 1993; 100: 576-578). This is too low in order to produce typical prolongations of more than 100%, as occur with high lupus anticoagulant and therefore not adequate for standardization using.a wide measuring range.
It has also been described that annexins under certain circumstances can lead to a prolongation of the APTT.
This family of intracellular proteins at present includes at least eight characterized proteins which are designated according to. the new nomenclature as annexin I to VIII (Römisch, J. et al., Biol, Chem. Hoppe Seyler 1990; 5: 383-388). These proteins have an inflammation-modulating action in that they are released from cells on inflammation and bind to membrane surfaces and thereby inhibit the binding of phospholipase A2, an important step for the formation of arachidonic acid derivatives having an inflammatory activity. By means of this calcium-dependent binding to phospholipid surfaces, the clotting processes taking place on these surfaces are also disturbed, which is why these proteins are also designated as “vascular anticoagulant”. Typically, the presence of annexins leads to a prolongation of the APTT in a concentration-dependent manner (Römisch et al. Thrombosis Research 1990; 60: 355-366).
Until now, however, it was unknown whether annexins could fulfill all criteria comparably to a natural lupus anticoagulant. The following criteria are used for the functional diagnosis of a lupus anticoagulant (Brandt, J. T. et al., Thrombosis Haemostasis 1995; 74: 1185-1190):
1. Prolongation of the clotting time beyond the normal range in at least two tests, in particular the APTT and the RVVT.
2. Proof that this prolongation is phospholipid-dependent and can be neutralized either by addition of phospholipids or by use of the same reagents as in 1. only with higher phospholipid concentrations.
3. Differentiation of a possible factor deficiency by plasma exchange experiments, in which case, in a 3+1, 1+1 and 1+3 mixture with a normal plasma in a clotting test, preferably the APTT, this prolongation is characteristically only neutralized by a high dilution (1+3), while in the case of a factor deficiency this is already clear earlier.
4. Differentiation of an acquired inhibitor (auto antibody against a clotting factor), in particular against Factor IX or Factor VIII (acquired hemophilia A or B) wherein this only acts in one of the two clotting pathways (intrinsic or extrinsic pathway), while a lupus anticoagulant non-specifically affects all phospholipid-dependent stages in clotting tests.
Surprisingly, it was now possible to show that by the suitable use of annexins a lupus anticoagulant standard or control preparation can be prepared which fulfills all the criteria described above.
Example 1 shows the prolongation of the customary diagnostic
Dade Behring Marburg GmbH
Finnegan, Henderson Farabow, Garrett and Dunner L.L.P.
Ludlow Jan
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