Chemistry: analytical and immunological testing – Sedimentation rate or hematocrit
Patent
1999-03-31
2000-10-03
Warden, Jill
Chemistry: analytical and immunological testing
Sedimentation rate or hematocrit
436 66, 436 10, 436 45, 436 63, 435 2, 435 724, 435 725, 422 72, 422 73, G01N 3380
Patent
active
06127187&
DESCRIPTION:
BRIEF SUMMARY
APPARATUS AND METHOD FOR ANALYSING BLOOD SAMPLES
This invention relates to improved apparatus and method for analysing blood samples.
For analysis and diagnostic purposes it is known to place a sample of blood in a haematocrit tube and thereafter spin the tube on a rotor. The centrifugal force derived from the spinning action causes the various components or phases within the blood sample of different density to separate. Typically the red cells, which are of the highest density within a blood sample, will pack towards one end of the tube. Adjacent to the red cells will be a phase of white blood cells and adjacent to the white blood cells will be a phase of platelets. Further along the tube there may locate plasma of lighter density.
Once the haematocrit tube has been spun separating the various blood components it is known to then determine the percentage content or "count" of each component within the sample. To do this effectively the position of the interface between various phases must be identified with some level of accuracy.
It has been found however that the interface which occurs between the platelets and white blood cells can be hard to detect with a sufficient degree of accuracy. Thus, it is common for operators to estimate the position of the interface between the platelets and the white blood cells by experience or expectation rather than analysis or identification. This estimated percentage is then subtracted from the volume of both the white blood cell and platelet phases to determine the White Blood Cell Count.
The problem with this method is that it does not cater for extraordinary situations or samples. For example, platelets are known to aggregate and by so doing have a greater density which causes the platelets, when the haematocrit tube is spun, to mix with the other blood cells. Thus, when an operator measures the length of the white blood cell and platelet phases, in combination, and thereafter subtracts an estimated platelet volume there can result a sizeable error if there is no significant platelet phase because of the aggregation.
This method of determining the white blood cell count is also generally erroneous or inaccurate when there is an extraordinary high or low platelet content in the blood to be analysed.
It is recognised in the present invention that it would be advantageous if a more accurate method of determining the platelet content could be derived, such that the white blood cell count could also be determined with greater accuracy.
According to the present invention there is a method for obtaining a white blood cell count within a blood sample, the method comprising the steps of: centrifugal force, but only to such extent that the platelets are suspended in a plasma cloud; absorption and or transmission of the cloud; of the platelet cloud to determine the content or mass of platelets in the blood sample; packing of the red cells and white blood cells and there is a clear interface between the red and white blood cells; platelet phases; and and platelets in combination to determine the white blood cell count.
Preferably the blood sample is placed in a haematocrit tube which is first spun for approximately 15 seconds at a speed of approximately 10,300 revolutions per minute. This separates the cellular and aqueous components of the blood sample.
Preferably also the optical density of the various phases is determined by measuring the percentage transmission of an optic beam originating from an optical source, such as an infra-red laser, through the sample. Advantageously, this is performed while the centrifuge rotor rotates at a reduced speed of approximately 1000 revolutions per minute, during which a scanning arm holding the optical light source moves across the centrifuge rotor.
Preferably after the content of platelets has been determined the sample is again spun at a circular velocity of approximately 10300 revolutions per minute and for a duration of approximately five minutes to achieve optimum packing and separation of the red and white blood cell phases.
Appa
REFERENCES:
patent: 4156570 (1979-05-01), Wardlaw
patent: 4558947 (1985-12-01), Wardlaw
patent: 5260598 (1993-11-01), Brass et al.
patent: 5889584 (1999-03-01), Wardlaw
Wardlaw, S.C., and Levine, R.A. Quantitative Buffy Coat Analysis, JAMA (1983) JAMA 249:617-620.
Tran Huan
Warden Jill
Wilcox James L.
LandOfFree
Apparatus and method for analyzing blood samples does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for analyzing blood samples, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for analyzing blood samples will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-194407