Chemistry: analytical and immunological testing – Composition for standardization – calibration – simulation,... – Particle count or volume standard or control
Reexamination Certificate
1998-09-14
2002-03-26
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Composition for standardization, calibration, simulation,...
Particle count or volume standard or control
C436S013000, C436S015000, C436S016000, C436S017000, C436S018000, C436S063000, C424S532000, C424S533000, C424S534000
Reexamination Certificate
active
06362003
ABSTRACT:
FIELD OF INVENTION
This invention relates to a novel method to increase the system quality control capabilities of hematology instruments. The method has particular utility for instruments which measure (1) volume measured by D.C. current, (2) high frequency (RF) size, (3) opacity, and (4) light scatter to discriminate cell populations of blood. The method has found additional utility for instruments which measure (1) volume measured by D.C. current and (2) high frequency (RF) size. The method has also found utility for instruments that measure cell volume only by D.C. current.
BACKGROUND OF THE INVENTION
Quality control long has been a necessary and routine procedure in clinical hematology. Accuracy in the counting of red blood cells and white blood cells, including differentiating among the subpopulations of white blood cells is dependent, in part, upon the use of adequate control products and methods of using the control products. With the numerous types of equipment for particle counting now available, quality control by the use of control products is necessary, since the possibility of malfunctioning of the instrument is ever present. The traditional method of maintaining a quality control program for automatic particle counting equipment has consisted of providing fresh human blood as a whole blood standard. However, this fresh blood is usable for only one day, therefore, durable blood products were developed.
Hematology control products, which contain reference blood cell analogs, which monitor the accuracy and precision of blood cell counting devices are important. It is recognized that there is a present need for new methods of using blood cell analogs for maintaining the accuracy of white cell differentiation and other parameters when employing such blood cell counting devices.
The control products should approximate that of fresh whole blood as closely as possible. Attempts have been made to provide suitably sized particles in stable suspensions by the use of ragweed pollen, polystyrene, latex, various organic materials and fixed human red cells. None of these suspensions have proved suitable for use as a control product for white cell differentiation of at least four subpopulations of leukocytes.
The material used for maintaining quality control, hereinafter called a hematology control product or control product, can under specific circumstances be used also to calibrate hematology instruments. For the purposes of this invention, the control product used in the method to determine whether an instrument is properly functioning will contain one or more analogs suspended in a liquid media, which when analyzed simulates at least one physical or biological property of blood which the instrument is capable of analyzing. As used herein, an analog is defined as a particle which simulates at least one physical or biological property of a target population. As such, some automatic machines are able to analyze only certain components of a control product, despite the control product having additional parameter components susceptible to analysis by other machines. Heretofore, there has been an absence of methods developed for using a control product to provide quality control of the instrument's performance. Control products typically provide checks for at least four subgroups of leukocytes namely, lymphocytes, monocytes, neutrophils and eosinophils. Prior art use of control products have focused upon checking whether the instrument provides the proper count and percentage of the analogs. However, the method of this invention provides additional information to evaluate and diagnose instrument performance.
It is evident that a control product must accurately indicate, on a comparative basis, what a test sample of fresh blood constitutes with regard to the determinations in question. It is further evident how important it is for the control product to simulate fresh blood, since blood components, such as red blood cells, can hemolyze slowly and undergo changes in size and shape within hours after removal from a blood donor. Similarly, non stabilized white blood cells suffer degenerative changes.
In general, the process of the prior art for making analogs focused on using red blood cells which had maintained or reduced their original volume prior to fixation. Shrinking or expansion of the cells by manipulating their osmotic environment prior to fixation has had its limitations. Previously, shrinking or swelling non-human erythrocytes more than about 30% to 50% caused excessive cell association or lysis of the cell.
U.S. Pat. No. 3,873,467 to Hunt teaches a hematologic reference control comprising a suspension of washed, stabilized human red blood cells in a nonproteinaceous aqueous suspension fluid that replaces the plasma in human blood. Stability in the reference control is attained by conditioning the cells by the inclusion in the aqueous suspension fluid of materials tending to make the cells assume a spherical shape, without substantial change in the mean cell volume of the cells, as well as imparting to the cells a resistance to the normal tendency of degrading with time. The aqueous suspension fluid furthermore produces an environment for the cells inhibiting biological activity. In a preferred embodiment there is further included in the reference control a minor amount of fixed human red blood cells, processed to have a substantially increased mean cell volume. The fixed cells are resistant to a change in cell volume, and to dissolution under the action of lysing reagents producing lysing of the stabilized cells. The fixed red blood cells in the reference control substitute for the white cell population in human blood.
In U.S. Pat. No. 4,704,364, to Carver, et al., there are disclosed controls for thresholds and additional operational performances for electronic particle counters typified by the COULTER COUNTER® Model S-Plus type analyzers. However, there is now a need for new methods of using a whole blood cell control product for electronic optical particle counters typified by the COULTER® VCS analyzer. The VCS analyzer permits the differentiation of at least four populations of leukocytes.
Any system for automated differential counting of human leukocytes, which distinguishes at least four populations of leukocytes from other cells in the blood on the basis of size range, volume distribution, light scatter range, and electrical opacity and conductivity sensitivities requires that the control product closely simulate the range, distribution and sensitivities characteristics of the respective cells in normal human blood.
Human lymphocytes, monocytes, neutrophils, basophils and eosinophils have a specific size distribution range and optical characteristics. Both the upper and lower size limits for each subpopulation of leukocytes should be represented in a reference control product. In addition, the mean cell volume of each leukocyte subpopulation in the control product should approximate that of normal human blood. Moreover, it is necessary that the liquid suspension media used for the control product does not cause significant shrinking or swelling of the cells. Still further, the aging of the control product should not result in deterioration of the volume distribution histogram characteristics or other parameters. A further requirement for the leukocyte analogs in the control product for multi-parameter instruments is that in order to be counted and differentiated, the analog cells in a whole blood control product must not be completely lysed by the lytic reagent.
A variety of media have been used in conjunction with blood cell analogs. In U.S. Pat. No. 4,299,726, a multi-purpose diluent and a media is disclosed. The diluent is used to precondition red blood cells and consists essentially of lactose, sodium azide and a non-ionic surfactant; is pH adjusted and osmolality adjusted. The media is used for a carrier of the whole blood control product and includes lactose, fungicides and antibiotics. It also includes additional components which alter red blood cell m
Elliott Michael
Fischer Timothy J.
Naylor Nancy
Young Carole
Coulter Corporation
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Soderquist Arlen
LandOfFree
Hematological reference control composition containing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hematological reference control composition containing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hematological reference control composition containing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2837364