Chemistry: analytical and immunological testing – Automated chemical analysis – With a continuously flowing sample or carrier stream
Reexamination Certificate
1998-10-13
2001-12-25
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Automated chemical analysis
With a continuously flowing sample or carrier stream
C436S047000, C436S053000, C436S179000, C422S067000
Reexamination Certificate
active
06333197
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the field of haematological analysis, and more specifically to the fractionated distribution of a blood sample.
The expression “blood sample” in this case denotes a volume of blood obtained from a blood sample taken from a patient, and contained in an analysis container, which for example can be an open tube, or a tube closed by a stopper. In general the blood in question is whole or full blood, taken with an anticoagulant.
In haematological analysis, it is often necessary to obtain several fractions of the blood of a patient, which are still known as “aliquots”, and are destined to be diluted with different reagents in order to obtain different analysis results.
This is the case in particular for globule counters, which count and differentiate white globules.
For practical reasons, it is preferable to take only a single sample of the patient's blood in a tube, then to fractionate this sample into different aliquots, each of which will then be added to a suitable reagent.
For this purpose, fractionating of the blood sample by means of a sample valve is known, according to the teaching, for example, of publication FR 2 622 692 in the name of the applicant.
These sampling valves have the advantage that they operate at high speeds, which makes them particularly advantageous for specific types of analysers.
However, their main disadvantages are that they require volumes of blood which are far greater than the theoretical volumes necessary for the analysis, they have a complex and costly structure, and they additionally need frequent cleaning, which is difficult to carry out.
In the field of biochemistry, it is also known to collect all of a blood serum in a needle, and then to discharge various successive volumes of this sample, for the purpose of different dilutions.
This specific technique is used for a blood serum, in other words blood from which the globules have been removed, and which thus has lower viscosity than whole or full blood.
SUMMARY OF THE INVENTION
The object of the invention is in particular to eliminate the aforementioned disadvantages, and to permit fractionated distribution of a blood sample, in highly efficient conditions.
In particular, an object of the invention is to provide fractionated distribution, using means which are simple, reliable, and easy to maintain.
A further object of the invention is to permit distribution of this type on the basis of a minimal blood sample volume, without any risk of contamination of the reagents with one another, and in each case ensuring that an aliquot of blood is well mixed with the reagent concerned.
For this purpose, the invention provides a method for fractionated distribution of a blood sample, comprising the following operations:
a) drawing up a blood sample into a needle;
b) distributing via the needle an aliquot of blood, corresponding to a specific fraction of the sample drawn up, into a flow of a reagent, in order to produce a mixture of the aliquot and the reagent;
c) collecting the mixture in a mixing and/or measuring receptacle; and
d) repeating operations b) and c) at least once on another aliquot of the same sample, and another flow of reagent.
Thus, the method according to the invention makes it possible to fractionate a blood sample contained in a needle, into at least two aliquots which are each mixed by dilution with an appropriate reagent, in each case in a mixing and/or measuring receptacle.
As a result, each aliquot, which corresponds to a specific fraction of the sample, is forced into the flow of reagent, thus permitting thorough mixing of the blood and reagent to be analysed.
The aliquots have selected volumes which can be identical or different, thus providing the method according to the invention with considerable flexibility of use.
The above-described operation a) advantageously comprises drawing up the blood sample into the needle which already contains a fluid, a bubble of gas, for example of air, being formed on the interface between the fluid and the blood sample.
By this means, there is no risk of mixing taking place between the blood sample and the fluid, since the latter simply acts as an intermediary for drawing up the sample, and then for gradual ejection of this sample in various aliquots, according to the analyses to be carried out.
According to another characteristic of the invention, the blood sample is drawn up into the needle from a tube of an open or closed type, containing a volume of blood to be analysed.
The blood sample which is drawn up into the needle advantageously has a volume which is greater than the sum of the respective volumes of the aliquots to be distributed, such as to provide an optional excess of volume, in order to obtain an initial volume of blood in the needle on completion of the operation a), and/or a residual volume of blood in the needle on completion of the operation d), thus making it possible to keep the aliquots intact.
The initial volume of blood can be discharged before the fractionated distribution takes place.
The residual volume of blood alone is affected if there is residual fluid present before sampling of the blood takes place. This residual volume can be discharged after the distribution, for example into a rinsing vessel, which allows the needle to be used to collect a further blood sample.
According to a further characteristic of the invention, the operation b) comprises injection of the aliquot of blood and injection of the flow of reagent under controlled conditions, and substantially simultaneously.
According to a preferred embodiment of the invention, this operation b) comprises in succession:
b1) injection of an initial part only of the flow of reagent;
b2) simultaneous injection of the aliquot of blood and of an intermediate part of the flow of reagent; and
b3) injection of a final part only of the flow of reagent.
According to a further characteristic of the invention, in operation b), the flow of reagent is injected such that this flow reaches the end of the needle by means of which the aliquot of blood is injected.
The aliquot of blood is preferably injected in a substantially vertical descending direction, whereas the flow of reagent is injected in a direction which is horizontal or inclined relative to the horizontal, such as to assist rotary motion or eddying, thus permitting thorough mixing of the blood and the reagent.
The method according to the invention can comprise at least one additional operation, consisting of depositing an aliquot of blood in a fluid medium or on a solid support, for example on a glass plate.
This makes it possible to combine operations of mixing aliquots and reagents, with operations of a different kind.
According to another aspect, the invention relates to a device for implementation of the above-described method, comprising:
a needle which can draw up a blood sample;
a first volumetric distributor, which is connected to the needle, in order to draw up and eject selected volumes of blood;
at least one reagent injection nozzle, which can be disposed in the vicinity of the end of the needle;
a second volumetric distributor, which is connected to the nozzle, in order to eject selected volumes of a flow of reagent;
a control unit which is connected to the first volumetric distributor and to the second volumetric distributor (s), in order to actuate the latter in a coordinated manner; and
at least one mixing and/or measuring receptacle, in order to collect the mixture formed from the blood and the reagent, which are distributed respectively by the needle and the injection nozzle.
The injection nozzle is preferably oriented towards the open end of the needle, via which the blood is ejected.
The needle is advantageously substantially vertical, with its open end facing downwards, whereas the injection nozzle extends in a direction which is horizontal or inclined relative to the horizontal.
The injection nozzle is advantageously integral with a mixing and/or measuring receptacle.
This receptacle can be a vessel which is delimited by a peripheral wa
Champseix Henri
Le Comte Roger
A B X
Cross LaToya I.
Dennison, Scheiner Schultz & Wakeman
Wallenhorst Maureen M.
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