Chemistry: analytical and immunological testing – Including sample preparation – Dilution
Reexamination Certificate
1999-01-29
2001-09-04
Kim, John (Department: 1723)
Chemistry: analytical and immunological testing
Including sample preparation
Dilution
C422S081000, C422S105000, C422S105000, C436S052000, C436S180000
Reexamination Certificate
active
06284548
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a blood testing method, and more particularly a method for performing a dilution step in a blood testing apparatus. The invention also concerns a blood testing apparatus adapted for performing dilution of a blood sample.
BACKGROUND OF THE INVENTION
When using a blood testing apparatus, a blood sample is normally taken by venipuncture. The blood is introduced into a small tube containing, for instance, 5 ml. From this tube, blood is sucked into a charging tube of the apparatus. Suction is stopped when the blood reaches a detector indicating that a sufficient amount of blood has been introduced into the apparatus. A well-defined volume of the blood sample, typically 25 &mgr;l, is flushed by a defined volume, typically 5 ml, of a diluting liquid into a mixing vessel, where the sample is pre-diluted to typically 1:200. The diluted sample is further diluted 1:200 to a dilution ratio of 1:40000 for counting red blood cells and 1:1 to a dilution ratio of 1:400 for counting white blood cells.
When, however, a sample is taken from a finger tip, which is often practised when children are involved, the blood volume is small and is not sufficient for sucking into the apparatus for dilution as described above. Instead, a manual dilution procedure is practiced. The blood sample is manually collected in a small vessel and a defined volume thereof, typically 25 &mgr;l, is introduced into a small diameter glass tube, i.e., a capillary tube often referred to as a “microcap ”, or a “mini ” or “micro ” pipette, which sucks the sample by capillary action. The volume contained in the capillary tube is pre-diluted 1:200 by means of a separate dispenser. This pre-diluted sample is then sucked into the apparatus, whereupon final dilution takes place as when a venipuncture test is performed. However, this procedure is circumstantial in that it requires an extra manual step.
It would be desirable, thus, to simplify the procedure when making blood tests by way of finger tip puncture, and it is the object of the present invention to provide a method and a device that enable this.
SUMMARY OF THE INVENTION
According to the present invention, the blood sample is initially introduced, as before, in a capillary tube. The capillary tube is placed in an adapter, which is placed in a conduit from a source of diluting liquid to a mixing vessel where the sample is directly pre-diluted, typically 1:200. The manual pre-dilution step is, thus, superfluous. The capillary tube may remain within the adapter until another capillary tube having a new sample is inserted, since the used capillary tube may be regarded as just an empty glass tube.
More specifically, the method of the present invention for performing a diluting step in a blood testing apparatus of a small, defined volume of a blood sample contained in a capillary tube comprises the steps of providing an adapter for receiving the capillary tube; connecting the adapter to a conduit for diluting liquid; directing a flow of diluting liquid through the conduit and the adapter and at least partly through the capillary tube received therein; and collecting the defined volume of blood sample and the diluting liquid in a vessel.
In a blood testing apparatus according to the present invention adapted for diluting a small defined volume of a blood sample contained in a capillary tube, the apparatus including a diluting liquid conduit, an adapter is inserted in the diluting liquid conduit, the adapter being arranged to receive the capillary tube such that flow of diluting liquid through the diluting liquid conduit passes at least partly through the capillary tube.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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Boule Medical AB
Kim John
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