Chemistry: analytical and immunological testing – Clotting or clotting factor level tests
Reexamination Certificate
1999-02-08
2003-02-18
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Clotting or clotting factor level tests
C436S018000, C436S063000, C436S066000, C422S073000, C600S369000
Reexamination Certificate
active
06521460
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of carrying out blood tests.
BACKGROUND OF THE INVENTION
Many diverse blood tests are required for diagnosing, in particular, internal diseases and for controlling the course thereof. These blood tests can be divided into tests regarding the cellular blood components (blood count, differential blood count, blood group, immunophenotyping of blood cells) and into serum tests and also into antibody screening tests, Coombs tests and cross-matching tests. Serum tests are concerned with the determination of enzymes, metabolic products (e.g. creatinine, urea, blood sugar) and coagulation parameters. In addition, special tests, such as hormone analyses or drug level analyses, are carried out on the basis of serum.
With seriously ill and hospitalized grown-up patients, enlarged blood tests have to be carried out over a prolonged period of time every day and sometimes even twice a day to detect critical changes in the physical condition of the patient at an early stage. Blood is taken under sterile conditions normally using a closed blood taking system by puncturing a vein in the bend of the elbow (e.g. V. cubita mediana). Blood is optionally taken through already laid central indwelling catheters. Depending on the clinical requirements and the desired laboratory tests, types and numbers of the tubes to be filled with blood are defined. Specific laboratory tests can only be carried out with specific substances specifically prepared for such tests (e.g. specific anticoagulants (heparin, EDTA, citrate, etc.)) or with glucosidase inhibitor (“blood sugar tubes”) or blood withdrawing tubes containing coagulation-promoting substances (“serum tubes”). Heparin and EDTA are unspecific, indirect inhibitors. They do not act directly or specifically on a specific element of the blood coagulation cascade, but their effect is of an indirect nature in that they intercept, for example, Ca
2+
ions which, in turn, are essential for the activation of different proteins of the coagulation system. A uniform pretreatment of the blood to be tested (“standard tube”), on the basis of which all or at least the majority of important blood tests could then be carried out, does not exist. Furthermore, it follows from the standard logistic sequence in clinico-chemical or hematological laboratories that a plurality of blood withdrawal tubes that have been pretreated in the same way are often needed. After withdrawal from the patient, and depending on the laboratory values to be determined, the blood tubes are transferred into laboratories that are most of the time separated spatially (most of the time a clinico-chemical laboratory and a hematological laboratory and optionally laboratories for special tests, such as immunophenotyping, drug level in the serum, etc. (material dispatch by mail or courier might here be necessary). The blood tubes received in the laboratory must first be sorted, and the tubes to be centrifuged are then centrifuged at about 3,500 r.p.m. for five minutes. The blood taking tubes are then forwarded to the different work places (coagulation tubes to the coagulation place, serum tubes for electrolyte determination on the flame photometer, etc). The respective automatic analyzing devices are then loaded with the samples, with the sample volume of about 10 &mgr;l to 100 &mgr;l, which is needed for one measurement, being very small in most measuring operations. The actual measuring operation lasts from a few seconds to a few minutes (five minutes at the most, depending on the method and the device). The measured values are finally printed out and, depending on the origin, are communicated in writing to the dispatching stations.
In summary, it is necessary at the moment that several blood taking tubes (depending on the desired test) should be filled with 2-10 ml blood (depending on the tube size) in a blood taking process. The following tubes are needed for determining the routine laboratory parameters:
blood count and differential blood count
1 × EDTA tube
sodium, potassium in the serum
1 × serum tube
liver enzymes and/or
1 × serum tube
creatinine and/or
urea and/or
lipase and amylase and/or
creatinine kinase and/or
cholesterol and triglycerides and/or
lactate dehydrogenase
total protein and protein electrophoresis
1 × serum tube
glucose in the serum
1 × glucose tube
Quick, PTT
1 × coagulation tube
(citrate)
blood sedimentation rate
1 × BSR tube
total
7 tubes
If, in addition, the blood group has to be determined and an antibody screening test has to be carried out and erythrocyte concentrates have to be provided for, two further blood taking tubes (without additions) have to be taken. In the case of special tests that are required, e.g. hormone level analyses (T3, T4, TSH basal, etc.), drug level (digitoxin level, vancomycin level, theophylline level, etc.), special electrolyte concentrations (magnesium, calcium, phosphate) and special coagulation values (deficiency in factors, fibrin degradation products), and many others, an additional withdrawal tube (most of the time serum tube) is needed for each test as a rule.
Hence, independently of the blood taking system, the following serious drawbacks are found in these blood taking methods that have so far been in general use:
1. The daily blood withdrawals which must be performed in the case of seriously ill patients lead to a blood loss of about 250 ml per week. This is an amount approximately half the blood donation amount of a healthy person at the German Red Cross. Another drawback is that seriously ill persons often suffer from anemia caused by very different factors.
2. The many blood withdrawing operations that are required are a considerable cost factor in medical care; on the one hand, because of the purchasing costs and, on the other hand, because of the considerable disposal costs for the tubes. The blood tubes used are classified as infectious wet waste and must be burnt being packed in special containers. In the case of seriously ill persons about 40 blood taking tubes are needed every week.
3. The workplace classification which is defined and segmented by the differently pretreated blood samples (anticoagulated whole blood for blood count determination, serum for enzyme tests and electrolyte determinations, etc.) and by the automatic measuring devices adapted thereto requires a multitude of work places entailing correspondingly high costs with respect to personnel and financing.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a method for carrying out blood tests, whereby the above-mentioned drawbacks can be overcome and many blood measuring parameters can be determined rapidly and reliably within a short time interval almost at the same time.
This object is achieved by a method according to claim 1. The achievement of such an object is, in particular, due to the finding that almost all of the clinico-chemical blood parameters can be determined using not only blood serum, but also blood plasma provided such blood plasma—in contrast to standard practice—has been prepared by adding a thrombin inhibitor, such as hirudin. The difference between serum and plasma is that the first one is free from fibrin whereas the latter still contains fibrinogen. Surprisingly enough, it has been found that one and the same blood sample can be used for determining both clinico-chemical parameters and hematological parameters provided the sample is mixed with a thrombin inhibitor. Preferably, hirudin and/or desulfatohirudin is/are used as thrombin inhibitor. This method can be carried out in an automated manner.
Hirudin is a highly specific thrombin inhibitor which is naturally found in the salivary gland secretion of leeches, Hirudo medicinalis. The anticoagulative activity in salivary gland secretions of Hirudo medicinalis was described by Haycraft for the first time about 100 years ago (Haycraft, J. B. (1894), Naunyn-Schmiedebergs Arch. Exp. Pathol. Pharmakol. 18, 209). In the fifties Markwardt et al. succeeded in
Melber Karl
Menssen Hans Dietrich
Strasser Alexander W. M.
Thiel Eckard
Rhein Biotech Gesellschaft fur Neue Biotechnologische Prozesse u
Swanson & Bratschun LLC
Wallenhorst Maureen M.
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