Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Reexamination Certificate
1999-06-25
2002-04-02
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
C422S073000, C422S091000, C422S105000, C436S069000, C436S070000, C436S174000, C436S177000
Reexamination Certificate
active
06365104
ABSTRACT:
TECHNICAL FIELD
This invention relates to the analysis of centrifuged anticoagulated blood samples which are contained in a centrifuge tube having a blood constituent-elongating insert therein. More particularly, this invention relates to a centrifuge tube assembly which is useful for measuring various blood parameters such as hematocrit, and which is also designed to examine the blood sample for evidence of rare events such as: blood-borne cancer cells; malarial parasites; other hemato-parasites; bacteria; or the like. The blood sample can also be analyzed in the tube for hematocrit and hemoglobin values as well as white cell and platelet counts.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,027,660 granted to Stephen C. Wardlaw et al describes a method and paraphernalia for use in measuring differential white cell and platelet counts in a centrifuged sample of anticoagulated whole blood. The procedure described in this patent suggests that a scale be used to measure the length of physically expanded white cell and platelet layers, and that a table be used to convert the measured layer lengths to definitive blood cell and platelet layer counts. U.S. Pat. Nos. 4,156,570 and 4,558,947 granted to Stephen C. Wardlaw disclose instruments which are used to measure cell and platelet counts in centrifugal blood samples contained in the aforesaid tube-insert paraphernalia, which instruments include microprocessor controllers that are programmed to automatically convert measured erythrocyte and platelet layer band lengths into cell and platelet counts. U.S. Pat. No. 4,259,012 granted to Stephen C. Wardlaw, and U.S. Pat. No. 5,132,087 granted to Kristen L. Manion et al describe devices for measuring white cell, platelet and hematocrit counts, which devices do not require conversion tables or microprocessor controllers. U.S. Pat. No. 4,209,226 granted to Stephen C. Wardlaw et al describes an optical viewing instrument which includes a capillary tube and a holder which includes a slot for containing the capillary tube. U.S. Pat. No. 4,190,328 granted to Robert A. Levine et al describes a process for the detection of blood-borne parasites wherein a centrifuge tube with an insert are used to trap blood-borne parasites between the tube and the insert so that the parasites will be visible under magnification through the tube.
The aforesaid group of patents all relate to inventions which utilize a tube and insert combination to either measure blood sample parameters quantitatively; or detect the presence or absence of blood-borne parasites, such as malarial parasites, microfilaria, or the like. In the latter case, the blood samples in the tubes are examined immersed in oil and under magnification, typically with an epi-illuminating UV or fluorescence microscope such as described in U.S. Pat. No. 5,198,927, granted Mar. 30, 1993 to R. R. Rathbone et al; and U.S. Pat. No. 5,349,468, granted Sep. 20, 1994 to R. R. Rathbone et al. When the centrifuged blood sample is being analyzed for parasites, or for blood borne rare events, there is currently no way to positively ascertain the location of the evidence of rare events in the centrifuge tube. The reason for this fact is that analysis of the blood sample in the tubes requires that the tubes be rotated so that the blood layers trapped between the tube wall and the insert can be thoroughly examined throughout the entire three hundred sixty degree circumference of the tube.
Present closures of capillary tubes are of three different varieties: simple clay, which is pressed into the tube from a tray; an internal closure described in U.S. Pat. No. 5,325,977 granted Jul. 5, 1994 to J. L. Haynes et al; and caps of the type shown in U.S. Pat. No. 5,132,087, granted Jul. 21, 1992 to K. L. Manion et al, and also shown in other issued patents.
To accurately measure the hematocrit height one must be able to accurately locate the lower and upper end of the packed erythrocyte layer. To examine centrifuged samples of blood for rare events, one must be able to position the objective of a microscope proximate the tube. The degree of sample magnification needed to examine the sample for rare events is generally 50×. Microscopic examination of the sample generally requires the use of an oil immersion for the tube on the microscope stage, and an objective lens which has a working distance of at least one hundred sixty microns. During the sample examination, the objective lens of the microscope must be disposed closely adjacent to the surface of the tube, or even touching the tube through the oil layer.
During microscopic examination of the sample, the tube must be manually rotated about its axis using one's fingers so as to be able to examine the entire circumference of the tube in the areas of interest. The areas in the blood sample which are of interest for rare events can include the areas in the blood sample which surround the portions of the insert which are submerged in the erythrocyte layer, and which are surrounded by both erythrocytes, buffy coat components, and, in some ases, by plasma at the upper end of the insert.
Closures of the aforesaid first and second types, while permitting accurate detection of the lower and upper ends of the erythrocyte layer, and permitting the the oil-immersed microscope objective to contact the capillary tube, do not facilitate accurate rotation of the oily tube and closure. The reason for this is that the glass tube and closure are smooth , and are frequently covered with oil thereby rendering the tube assembly extremely difficult to rotate when rotational pressure is manually applied with one's fingers. Furthermore, if manual pressure is applied to the tube assembly, the tube might fracture, thereby destroying the sample and potentially injuring the technician.
Closure caps of the third type described above, while not impeding manual rotation of the tube by means of manual contact with the cap, do render detection of the lower end of the erythrocytes difficult because the lower end of the erythrocyte layer will be obscured by such closure caps. A person with severe anemia, or one experiencing abdominal bleeding, can have a hematocrit of about twenty or less. In cases of such low hematocrits, i.e., hematocrits which are below levels of about twenty, the upper end of the packed erythrocytes may be positioned at or near at the upper edge of the cap, thereby rendering the upper end of the packed erythrocyte layer difficult to detect and obscured by the closure cap. Thus, when using closure caps of the aforesaid third type, hematocrit measurement may be difficult, or impossible to perform.
When microscopical rare event examination is attempted of the centrifuged blood sample in a tube-and-insert assembly that utilizes the aforesaid third type of closure, one may be unable to position the objective lens set of the microscope sufficiently close to the sample tube to examine appropriate portions of the centrifuged sample due to mechanical interference between the microscope's objective lens set and the tube assembly closure cap. Thus, in all centrifuged blood samples which are contained in an assembly that employs the aforesaid third type of closure cap, at least a portion of the expanded portion of the erythrocyte layer which surrounds the float cannot be examined under a microscope for rare events, and in a blood sample with a hematocrit of less than about twenty, none of the expanded portion of the erythrocyte layer which surrounds the float can be examined under a microscope for rare events. Thus, while the third type of closure cap may allow manual rotation of an oily sample tube assembly, such a sample tube assembly limits the ability to microscopally examine the expanded portion of the erythrocyte layer which surrounds the float for the presence or absence of rare events.
The problem which is encountered in the examination of the blood samples for hematocrit relates to the fact that the closures of the third type entrap a significant portion of the erythrocytes, thereby lowering the upper end of the erythro
Brinster Wayne L.
Levine Robert A.
Wardlaw Stephen C.
Becton Dickinson and Company
Handy Dwayne K
Jones William W.
Warden Jill
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