DEVICE AND METHOD FOR WHOLE BLOOD SEPARATION AND ANALYSIS

Abstract: A method and device (10) for separating blood into fluid and cellular fractions for diagnostic tests. The whole blood (34) is introduced to a carrier (36) containing a layer of car­ bohydrate and reagent material which results in the rapid separation of the fluid (38A) from the cellular fractions (38). In a preferred embodiment, the device is fabricated in a sandwich design containing the layers of carbohydrate and reagent ma­ terial between two layers of plastic.

Description: The detection of various soluble constituents in whole blood has been found to be particularly difficult. These tests usually are dependent on the visual and instrumental measurement of chromogen color formation to detect the soluble constituents. The red color of the hemoglobin therefore seriously interferes with the analysis and observations for a positive response. These tests can be simplified by prior separation of the red blood cells from the sample of whole blood. Indeed, diagnostic tests frequently require this separation. One of the conventional methods of separating the cellular fractions from the fluid of whole blood is by centrifuging. This method of separation is very time consuming, complicated and requires extra manipulative steps and expensive laboratory apparatus. The blood is placed in a container and spun until the cellular fractions are forced to the bottom of the container and the fluid which is to be tested remains at the top. The next step is to separate the fluid from the cells by removal with a pipette. The fluid is then placed in a second container for subsequent analysis. Great care must be taken when pipetting the fluid from the separated blood cells because there is a zone where the cells and the fluid are intermixed. Careful attention and effort is therefore necessary to ensure that the fluid is substantially cell free. Prior methods of separating cellular fractions from fluid in whole blood have been described in US-A-3,552,925, US-A-3,552,928, and US-A-3,146,163. These patents disclose the use of certain soluble and insoluble materials to effect a separation of the cellular components and the fluid. Various proposals have been made to handle analysis of whole blood directly without a preliminary separation of fluid and cellular fractions. GB-A-2 008 246 describes a method and apparatus for chemical analysis of e.g. a blood sample with reagents spotted on a fibrous or porous medium pretreated with reagents and a conditioning agent including a thickening agent and surfactant. Mannitol is amongst several conditioning agents mentioned therein. Improved sample wetting during testing is obtainable by means of the conditioning agents. Thus spreading of sample and reagents through the porous medium is inhibited. Diffusion of a sample deposited on a gel medium is relied on under controlled conditions of time in a method described in GB-A-2 025 044 whereby a precise aliquot of sample in the gel mass is said to be obtainable. A further GB-A-2 029 012, comments on the difficulties of obtaining in a given time period a true reading of whole blood components in an assay of whole blood deposited on a porous substrate. This being due to varying amounts of red cells from sample to sample which by surface occlusion affect the absorption and diffusion rate of the fluid components of the blood. It proposes a means of obtaining correction factors for adjusting values by monitoring diffusion of an inert substance across the porous substrate. A further patent publication, EP-A-0 130 335, describes the use of a reagent layer e.g. filter paper affixed to a support, which layer has a partially cross-linked polymer upper layer which may be a carbohydrate. The upper layer is contacted with sample and since the cross-linked polymer is intended to bar penetration of proteinaceous matter, target soluble components are absorbed and may reach the reagent system whilst excess sample including interfering pigmented matter may be wiped off. Even so, simplicity of operation and ease of use remain desirable objectives despite such known attempts at in situ separation and analysis. It is therefore an object of this invention to provide a simple one step method for whole blood separation and analysis. It is a further object to provide a novel method and device for efficiently separating the whole blood into fluid and cellular fractions to facilitate subsequent diagnostic testing. The novel method and device of this invention provides a rapid one-step process for the simultaneous separation of the fluid from the whole blood and testing for the desired component. The method provides for IN SITU separation which is much more simple, less expensive and more rapid than prior methods. Briefly, this invention consists of a testing or sampling device which comprises a carbohydrate applied to an impermeable carrier. The device also provides a carrier treated with specific reagents or diagnostic compositions which result in a chemical reaction with the fluid component. Thus according to the invention there is provided a test device for separating the fluid portion from whole blood and detecting soluble components in whole blood which comprises a first impermeable carrier having applied thereon a sugar, mannitol, sorbitol or inositol in a dry powdered form and a second impermeable carrier having incorporated thereon a test reagent specifically reactable with component to be detected; said first and second carriers being affixed to one another along substantially their entire juxtaposed peripheral edges, but having an opening between said juxtaposed peripheral edges; the carriers being so layered that the sugar and reagent are in contiguous facing relationship; wherein said opening and carriers permit capillary and longitudinal transport of the blood. On a portion of one carrier a column of powder is coated and the second carrier is coated with reagents which are specific to detect a desired blood component. The separate carriers are then laminated so that the powder and reagents are in contiguous relationship. An opening in the laminated device is provided whereby the blood can directly contact the porous material. According to this invention the method for separating whole blood into fluid and cellular fractions comprises applying the blood to the testing device of this invention whereby the cellular fraction remains in close proximity to the site of contact and the fluid fraction migrates in a longitudinal fashion away from said site. If the carrier is further treated with a specific reagent employed to detect the component tested for, a color will appear in the fluid portion. An exogenous analysis can be carried out by removing a portion of the carrier containing the clear fluid with a punch and then adding the reagent. In the method of the invention the whole blood is contacted with the carbohydrate column which preferentially absorbs the colorless blood component free of cells. The cellular fraction remains at the bottom of the column and the clear fluid proceeds above the cellular fraction and comes in contact with the reagent employed to detect a specific blood component. The reaction between the component being tested for and the test reagent are then observed. These methods thus provide a simultaneous means for separating cellular and fluid fractions of the whole blood and analyzing the fluid portion. Exemplary of impermeable carriers which may be employed in this invention are any plastic sheet materials such as polyesters, polycarbonates, polystyrenes, polyvinyl polymers, polypropylene, polyethylene, polyethylene terephthalate (Trade Mark: Mylar), ethylcellulose and cellophane. Other impermeable carriers such as glass or wax paper may be used. Most advantageously, the side in which the results are observed will be of a transparent material and the opposite panel will be of an opaque material in order to provide a reflective background. Preferable carbohydrates which can be employed are sugars or sugar alcohols such as: Most advantageously mannitol is employed in the device of this invention. In regard to the reagents, the device would contain the reagent specific for the detection of the blood component being sought. For example, if testing for glucose in the blood, tetramethylbenzidine, glucose oxidase and peroxidase which are well known reagents for detecting glucose would be used in the device. The following soluble blood components are some examples of those which may be tested for in the method according to this invention: An additional advantage of the present invention is that the soluble blood components are not affected by the carbohydrate filtration. At least ninety percent of the component found in the conventionally prepared serum is found in the fluid filtered by the separation process of this invention. A detailed description and better understanding of this invention can be had by referring to the accompanying drawings which show a preferred embodiment of the present invention. FIG. 1 is a perspective view of the preferred embodiment of the testing device. FIG. 2 is an enlarged sectional view taken on line 2-2 of FIG. 1. FIG. 3 is a greatly enlarged fragmentary sectional view of the details contained within the dot and dash circle of FIG. 2. FIG. 4 is an exploded perspective view illustrating the various sections of construction prior to lamination. FIG. 5 is a fragmentary view taken on line 5-5 of FIG. 4. FIG. 6 is a fragmentary view taken on line 6-6 of FIG. 4. FIG. 7 is a side elevational view illustrating a manner of use of the preferred embodiment of this invention. FIG. 7A is an enlarged fragmentary schematic view illustrating the separation of fluid from the blood cells and also indicative of a negative test. FIG. 8 is a perspective view of a modification of the preferred embodiment. FIG. 9 is an additional preferred embodiment of PIGS. 1 through 8 of the testing device. FIG. 10 is a perspective view of one segment of FIG. 9. FIG. 11 is still another embodiment of the device of this invention. FIG. 12 is an exploded perspective view of still an additional modification in which the carrier containing the carbohydrate is attached to a rigid support and encased in said support. FIG. 13 is a greatly enlarged fragmentary sectional view taken on the line 18-18 of FIG. 12. FIG. 14 is a further modification of FIG. 12 in which the carrier is not encased in the support. As illustrated in FIGS. 1 through 3, a device 10 for separating blood into fluid and cellular fractions in accordance with the invention has an impermeable carrier 12, such as Mylar (TM), having an opaque coating 20 and a clear backing sheet 16 such as polycarbonate laminated to the opaque carrier. The Mylar carrier has an adhesive precoat 11. The device has openings 10a and 10b which permit contact of the whole blood with testing area 36 which is composed of a band of dry porous material 14 such as a carbohydrate applied to the inner face of the opaque material. The backing sheet has a reagent material 18 specific to detect a desired blood component applied to its inner face. As noted in FIG. 3 the reagent and porous material 14 are in contiguous relationship after lamination. FIG. 4 discloses the structure of the device prior to lamination, i.e., the opaque carrier with a column of dry porous material and the clear backing sheet with the desired reagent. One method of use of the preferred embodiment is illustrated in FIGS. 7 and 7A. A puncture on the first finger 32 of the left hand 30 produces whole blood droplet 34. The testing device 10 is placed over the puncture in such a manner that the blood droplet contacts the testing area 36, which contains the column of dry porous material, through opening 10b. The blood travels by capillary action up the testing area and the porous material preferentially absorbs the fluid component of the blood 38A leaving the red cellular fractions 38 behind. In testing for a soluble blood component such as glucose, the specific reagent will stain the fluid portion as indicated at 40 if the test is positive. FIG.7A which illustrates the separation of fluid 38A from the red cellular fractions 38 is also indicative of a negative test. FIGS. 8 through 14 demonstrate further embodiments of the testing device of this invention. Modification 50 represents a series of devices strung together showing a plurality of panels 52 a - 52 e with lower terminal ends 54 tapering to the edges of the centrally located testing area. FIG. 9 illustrates a circular configuration of the devices shown in FIGS. 1-8 wherein multiple tests can be run. Blood can be applied to central portion 66 with a pipette 68 and the separation of the red cellular portion 70 from the fluid 72 can take place in any of the testing areas 64 a - 64 f present in wedge shaped sections 62 a - 62 f . In this illustration the fluid 72 is stained blue to show a positive test. Each of these wedge shaped sections may also contain different reagents in the testing areas for testing various blood components. FIG. 11 represents a rectangular shaped testing device 80 which also permits multiple testing. Blood can be applied to central portions 84 a - 84 d by pipette 86 and the separation and testing results can be observed in areas 82 a - 82 h which also may contain different reagents for testing separate blood components. A further modification of the device of this invention is illustrated as noted at FIGS. 12 through 14, where the absorbent material 124 and 126 is secured to rigid rectangular supports 120 and 120'. Referring to FIG. 12 the absorbent material 126 is encased with a plastic covering and a portion of the material 124 extends beyond the enclosure. The support has been removed from a test tube 122 containing the whole blood to be tested 122a and demonstrates a positive test at the color reactive zone 126a. FIG. 14 illustrates a modification of FIG. 12 showing the absorbent material 126 with the cellular zone 128 and color reactive zone (fluid zone) 130 not encased but completely exposed. The following examples serve to illustrate a method of preparing the testing device. Example 1 An alcoholic suspension of mannitol was prepared. The suspension was continually stirred while depositing the suspended powder onto approximately a 0.002 inch thick Mylar carrier with an adhesive precoat. The band of mannitol was deposited to the following dimensions, 0.25 inches wide and 0.004 inches thick. The suspended mannitol powder was thoroughly dried and overlaid with a plastic carrier. Example 2 A band of mannitol was prepared as in Example 1. A polycarbonate carrier coated with glucose oxidase, peroxidase, buffer and a chromogen combination was laminated to the mylar carrier. The resulting sandwich like structure was cut into appropriate size strips to be employed as testing devices.

Claims: A test device (10) for separating the fluid portion from whole blood and detecting soluble components in whole blood which comprises a first impermeable carrier (12) having applied thereon a sugar, mannitol, sorbitol or inositol in a dry powdered form (14) and a second impermeable carrier (16) having incorporated thereon a test reagent (18) specifically reactable with a component to be detected; said first and second carriers being affixed to one another along substantially their entire juxtaposed peripheral edges, but having an opening (10a, 10b) between said juxtaposed peripheral edges; the carriers being so layered that the sugar and reagent are in contiguous facing relationship; wherein said opening and carriers permit capillary and longitudinal transport of the blood. The device of claim 1 wherein the first carrier is a polyester and the second carrier is a polycarbonate. The device of claim 1 or claim 2 wherein the first carrier is opaque and the second carrier is transparent. The device of any one of claims 1 to 3 wherein the first impermeable carrier is coated with mannitol. A method for separating whole blood into fluid and cellular fractions which comprises applying the blood to the device of claim 1 whereby the cellular fraction remains in close proximity to the site of contact and the fluid fraction migrates in a longitudinal fashion away from said site. The method of claim 5 wherein mannitol is employed in said device.

Inventors: RAPKIN, MYRON COLMAN, SCHOENGOLD, RONALD JOSEPH, SHOCKEY, DAVID RAY, VAN RYSSELBERGHE, PIERRE CHARLES
Applicants: SMITHKLINE DIAGNOSTICS, INC.
Application year: 1986
Main classification: G01N33
IPC codes: G01N33