Surgery – Diagnostic testing – Liquid collection
Reexamination Certificate
1999-12-02
2001-08-28
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Liquid collection
Reexamination Certificate
active
06280400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a device and method for separating heavier and lighter fractions of a liquid sample. More particularly, this invention relates to a device and method for collecting and transporting liquid samples whereby the device and liquid sample are subjected to centrifugation in order to cause separation of the heavier fraction from the lighter fraction of the liquid sample.
2. Description of Related Art
Diagnostic tests may require separation of a patient's whole blood sample into components, such as serum or plasma, the lighter phase component, and red blood cells, the heavier phase component. Samples of whole blood are typically collected by venipuncture through a cannula or needle attached to a syringe or an evacuated collection tube. Separation of the blood into serum and red blood cells is then accomplished by rotation of the syringe or tube in a centrifuge. Such arrangements use a barrier for moving into an area adjacent the two phases of the sample being separated in order to maintain the components separated for subsequent examination of the individual components.
A variety of devices have been used in collection devices to divide the area between the heavier and lighter phases of a fluid sample.
The most widely used device includes thixotropic gel materials such as polyester gels. The present polyester gel serum separation tubes require special manufacturing equipment to prepare the gel and to fill the tubes. Moreover, the shelf-life of the product is limited in that overtime globules may be released from the gel mass. These globules have a specific gravity that is less than the separated serum and may float in the serum and may clog the measuring instruments, subsequently during the clinical examination of the sample collected in the tube.
Moreover, while the gel is chemically inert to blood samples, if certain drugs are present in the blood sample when it is taken, there can be an adverse chemical reaction with the gel interface.
Therefore, a need exists for a separator device that (i) is easily used to separate a blood sample; (ii) is non-temperature dependent during storage and shipping; (iii) is stable to radiation sterilization; (iv) employs the benefits of a thixotropic gel barrier yet avoids the many disadvantages of placing a gel in contact with the separated blood components; (v) minimizes red cell film or red cell hang-up of a blood sample; (vi) minimizes cross contamination of the heavier and lighter phases of the sample during centrifugation; (vii) minimizes adhesion of the lower and higher density materials against the separator device; (viii) is able to function in a plastic or glass container; and (ix) can be used with standard sampling equipment.
SUMMARY OF THE INVENTION
The present invention is a vessel useful for collecting a sample of a fluid and, when subjected to centrifugation, separating the sample into a higher specific gravity phase and a lower specific gravity phase. The vessel of the invention includes an elongate tube that has an open end, a closed end and a sidewall. The sidewall has an outside surface and an inside surface and defines a receptacle with a central axis.
The vessel has a closure disposed to fit the open end of the tube thereby sealing the receptacle. Alternatively, both ends of the tube may be open, and both ends of the tube may be sealed by elastomeric closures. At least one of the closures of the tube may include a resealable septum.
The vessel also includes an elongate separator releasably positioned at the open end of the tube that has a resilient top portion and an elongate lower portion. The elongate lower portion has an axial passage there through. The top portion is sized to fit releasably within the receptacle with an interference fit against the inside surface of the tube. When the vessel is subject to axial centrifugal force, the separator moves a distance axially from the open end toward the closed end.
The separator's position at the top of the receptacle and the separator's having a resilient top portion and a lower portion with a passage there through solves the problem of loading the sample into the tube between the separator and the bottom of the tube. The resilient top of the separator is easily penetrated by the sample delivery needle and thus the sample is delivered directly into the lower portion passage and the top surface of the separator is substantially not exposed to uncentrifuged sample. Then, when the vessel is centrifuged, the separator moves away from the open end of the tube and moves to a position between the lower and higher specific gravity phases of the sample. When the body fluid sample is blood, the higher specific gravity portions of the sample with the cellular components are between the separator and the bottom of the tube after centrifugation, and the cell free serum fraction is between the separator and the top of the tube. Since the separator moves axially down the tube inside surface during centrifugation and the sample is delivered into the tube below the separator, the interference fit between the separator top portion and the tube wall substantially eliminates the presence of red blood cells on the separator between the separator and the open end of the tube. The lower specific gravity serum phase of the sample is thus substantially free of cellular contamination.
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Becton Dickinson and Company
Thomas Nanette S.
Winakur Eric F.
Wingood Pamela L.
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