METHOD AND APPARATUS FOR COLLECTING BLOOD SAMPLE

Abstract: This invention relates to a method and apparatus for collecting a blood sample inside a blood collecting tube equipped with a film-like plug at its opening. A needle member capable of collecting blood components is penetrated through the film-like plug member and a portion near the tip of the needle member is placed in the blood sample. The blood sample is collected through this needle member while the inside of the blood collecting tube is shut off from the outside.

Description: TECHNICAL FIELD This invention relates to a method and apparatus for sampling a blood specimen in blood testing. BACKGROUND ART The following procedure ordinarily is adopted when attempting to sample a serum specimen in a blood test: First, blood is collected from a vein using a blood-collecting tube 80 (sealed by a rubber stopper 81), of the kind shown in Fig. 7, the interior of which is depressurized with respect to the atmosphere. Thereafter, the blood is subjected to centrifugal separation when it coagulates sufficiently. In order to extract a specimen solely from the serum layer obtained by separation, decantation or a sampling method using a pipette are available. Decantation refers to a method in which the rubber stopper is removed and only the serum from the upper layer is poured into a separate tube by hand. This state is illustrated in Fig. 8(a). In the method using a pipette, a pipette is inserted into the blood-collecting tube 80 via the opening from which the rubber stopper has been removed, and only the serum is sampled by the pipette. This state is shown in Fig. 8(b). Apparatus for performing these operations automatically are also available. In any case, it is necessary to remove the rubber stopper when sampling serum. When attempting to sample serum, therefore, some of the blood naturally spills out, and there is the danger that impurities will pierce the interior of the blood-collecting tube from the outside. Thus, major problems remain. In particular, when separated serum is divided several times for testing, sampling must be performed by repeating these sampling methods several times. This increases the possibility that the aforementioned difficulties will be encountered. U.S. patent 3,748,911 describes a device for taking samples of liquid specimens for use with an automatic analysis apparatus. The device comprises a sampling head including a hollow needle connected to a pump at one end. Optical or electrical means may be provided for positioning the needle relative to a test tube containing the liquid to be analysed. DISCLOSURE OF THE INVENTION The present invention has been devised in view of this prior art and attempts to provide a blood specimen sampling method and apparatus in which a process from blood collecting until sampling of an objective blood specimen is performed while a blood-collecting tube is kept closed, whereby the specimen inside the tube will not be spilled carelessly and impurities from the outside will not mix in with the specimen during this process. In order to solve the foregoing problems, the blood specimen sampling method of the present invention comprises the steps set forth below. Specifically, there is provided a blood specimen sampling method used in order to sample a blood specimen from a blood-collecting tube equipped with a film stopper at an opening thereof, said stopper comprising a gas-barrier film layer and a rubber layer for resealing on the gas-barrier film layer, said tube containing a blood specimen including a serum layer and a clot layer separated by a serum-separating agent layer, comprising the steps of: introducing a needle having a distal end into the interior of said blood collecting tube by moving downward a holding member which holds said needle and a sensor for detecting said serum-separating agent layer from the outside of the tube at a predetermined position downbelow said distal end of said needle; detecting said serum-separating agent layer by said sensor while introducing said needle into the interior of said blood collecting tube by penetrating said film stopper with said distal end of said needle; adjusting the position of said distal end of said needle to the predetermined position in said serum-layer by moving said holding member by a distance based on the relative distance between said distal end of said needle and a position of said sensing portion of said sensor after said sensor detects said serum-separating agent layer; and drawing a blood specimen into said needle from said distal end portion of said needle from only said serum layer. In accordance with a preferred embodiment of the invention, it is desirable that the method includes a step of piercing the film stopper with an air-introducing needle at least before the blood specimen is drawn in. This introduces air into the blood-collecting tube from the outside to facilitate the sampling of the blood specimen. The blood specimen sampling apparatus of the present invention has the construction set forth below. Specifically, there is provided a blood specimen sampling apparatus used in order to sample a blood specimen from a blood-collecting tube equipped with a film stopper at an opening thereof, said stopper comprising a gas-barrier film layer and a rubber layer for resealing on the gas barrier film layer, said tube containing a blood specimen including a serum layer and a clot layer separated by a serum-separating agent layer, comprising: introducing means for introducing a needle having a distal end into the interior of said blood collecting tube by moving downward a holding member which holds said needle and a sensor for detecting said serum-separating agent layer from the outside of the tube at a predetermined position downbelow said distal end of said needle; detecting means for detecting said serum-separating agent layer by said sensor while said introducing means is introducing said needle into the interior of said blood collecting tube by penetrating said film stopper with said distal end of said needle; adjusting means for adjusting the position of said distal end of said needle to the predetermined position in said serum-layer by moving said holding member by a distance based on the relative distance between said distal end of said needle and a position of said sensing portion of said sensor after said sensor detects said serum-separating agent layer; and drawing means for drawing a blood specimen into said needle from said distal end portion of said needle from only said serum layer. In accordance with a preferred embodiment of the invention, it is desirable that the sampling means include an air-introducing needle capable of introducing air into the blood-collecting tube from the outside thereof. This will make it possible to introduce air into the blood-collecting tube from the outside to facilitate the sampling of the blood specimen. The piercing operation of the sampling means is halted based on the results of detection performed by the detecting means. This facilitates situating the sampling means at the position of the serum layer. In accordance with a preferred embodiment of the invention, detection of the interface between the blood serum layer and the clot layer is performed by blood serum separating means such as a blood separating agent or blood separating float, and the detecting means detects the blood serum separating means. This makes it possible to detect the interface between the blood serum layer and the clot layer. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view illustrating the structure of a blood collecting tube in an embodiment; Figure 2 is a view showing a blood-sampling tube inserted in a blood-sampling holder; Figure 3 is a view showing blood being collected by the blood-collecting tube of the embodiment; Figure 4 is a view showing a serum sampling method; Figure 5 is a view showing the essentials of a serum sampling apparatus; Figure 6 is a flowchart for describing the operation of a controller in Figure 5; Fig. 7 is a sectional view of a conventional blood-collecting tube; Fig. 8(a) is a view showing a method of sampling serum by a decantation operation; and Fig. 8(b) is a view for describing a method of sampling serum using a pipette. BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will now be described in detail in accordance with the accompanying drawings. <Description of Blood-Collecting Processing (Figs. 1 - 3)> Fig. 1 is a sectional view of a blood-collecting tube. In this embodiment, the blood-collecting tube 20 is composed of a tube body 21 and a film stopper 24. The tube 20 is evacuated to negative pressure before blood is sampled from a living body. The structure of the stopper 24 will be described later. Fig. 2 is a view showing the blood-collecting tube of the embodiment when in use, and Fig. 3 is a view showing a state in which blood is sampled in accordance with the embodiment. The constituents and actions of the embodiment will now be described in due course. Numeral 22 denotes a blood-collecting holder having an opening into which the blood-collecting tube 20 is inserted. The blood-collecting holder 22 has a piercing needle 30 (hollow) which is secured by screwing a hub 31 onto a threaded portion 32 formed on the holder 22. A tip 30A of the piercing needle 30 having a pointed end to facilitate piercing of a living body. The piercing needle 30 has another end 30B also equipped with a pointed tip capable of piercing the film stopper 24 of the blood-collecting tube 20. The pointed end 30B is covered by a sheath-shaped flexible rubber cap 33. When blood is actually collected in the blood-collecting tube, first the blood-collecting holder is used to pierce the living body (a vein), after which the film stopper 24 of the blood-collecting tube 20 is inserted into the holder from the opening thereof so that the pointed end 30B of the piercing needle pierces into the blood-collecting tube 20, whereby blood is collected. <Description of Blood-Collecting Tube> The structure of the blood-collecting tube of the embodiment will now be described. As for the film stopper provided in the opening of the blood-collecting tube used particularly in this embodiment, use is made of one which, unlike the conventional rubber stopper, is capable of being pierced by the needle body of the blood specimen sampling apparatus and is thin enough so that the needle will not bend when piercing the stopper. Preferably, the film stopper comprises a laminated body of a gas-barrier film having a thickness of 20 - 200 µm and vulcanized rubber having a thickness of 0.3 - 2 mm. The tube body 21 of the blood-collecting tube in this embodiment is made of an acrylonitrile resin and is formed by an extrusion-blowing method (overall length: 100 mm, outer diameter: 14.4 mm, inner diameter: 13.4 mm). The film stopper 24 includes a gas-barrier film 24a [an acrylonitrile resin (brand name: Varex 210, manufactured by Mitsui Toatsu) 30 µm/vapor-deposited aluminum/nylon 15 µm) that is heated and caused to fuse with the opening of the tube body 21 under reduced pressure, and a natural rubber sheet 24b (diameter: 8 mm), having a thickness of approximately 1mm, bonded to the film by rubber cement. There is no limitation upon the material used to fabricate the tube body 21, and it will suffice if the material has a gas-barrier property. Accordingly, the material can be polyethylene, glass, etc. In accordance with this arrangement, a liquid-tight state can be maintained between the interior and exterior of the blood-collecting tube even if the piercing needle is removed after it has pierced the film stopper 24. A serum-separating agent 101 whitened by titanium white the main ingredient of which is α-olefin-dialkylmaleate copolymer is placed inside the tube body of the blood-collecting tube in this embodiment. Further, an unwoven fabric 103 coated with a coagulating-promoting agent is inserted in the tube body. <Description of Serum Sampling Processing (Fig. 4)> After blood has been sampled and collected in the blood-collecting tube 20 described above, centrifugal separation is applied following coagulation of the blood. A serum layer 100 is produced by this processing. In sampling the serum in this embodiment, the sampling is performed with the blood-collecting tube 20 kept sealed, without using decantation or a pipette. Specifically, after, say, an 18G syringe needle 40 pierces the film stopper 24 from the upper portion of the blood-collecting tube 20 and the needle tip (a cutting edge) reaches the serum layer, a predetermined amount of the serum is sampled (Fig. 4). Here the piercing resistance between the film stopper 24 and the syringe needle 40 can be a problem. In the present embodiment, however, the piercing resistance between the film stopper 24 and the syringe needle 40 is about 550 g and no difficulties are encountered. By way of example, the piercing resistance in a case where use is made of a stopper consisting of vulcanized butyl rubber or the like is as high as about 2100 g. With such a stopper, problems would arise such as bending of the syringe needle. The relationship between piercing resistance and the composition of the stopper used in serum sampling in this embodiment is shown in the table below, which illustrates average values each obtained from measuring piercing resistance five times. Further, A, B and C are shown in the evaluation column, in which A means that the syringe needle did not bend even after performing sampling using 100 blood-collecting tubes, B means that sampling is possible 50 times, and C means that sampling cannot be performed even 10 times. The table demonstrates that there is no limitation upon the composition of the stopper 24 described above. Specifically, it is permissible to bond aluminum foil (50 µm) instead of depositing aluminum. Preferably, the film stopper comprises a gas-barrier film having a thickness of 10 - 200 µm, and vulcanized rubber or elastomer having a thickness of 0.3 - 2 mm. A gas-barrier film whose thickness is less than 10 µm is too weak in strength, while one whose thickness is greater than 200 µm offers too much piercing resistance and has adverse effects both at the time of collecting blood and at the time of sampling. If the thickness of the vulcanized rubber or elastomer, which is for providing resealability, is less than 0.3 mm, the result will be a poor resealing property; a thickness in excess of 2 mm results in too much piercing resistance. It is permissible for the sampling needle to have a sharp, closed tip, with a hole being provided in the side thereof. As for the location pierced by the sampling needle, any point having the resealing rubber will suffice, though it is permissible to pierce the film portion. By piercing the film portion, a hole will be formed at the piercing since the film portion does not possess resealability. As a result, there will be no seal between the sampling needle and the hole and air from the outside will flow into the blood-collecting tube via the gap. Consequently, negative pressure will not develop inside blood-collecting tube at the time of sampling. In other words, the sampling operation can be performed smoothly. <Description of Serum Sampling Apparatus (Figs. 5, 6)> The apparatus for executing the foregoing sampling processing will now be described. Fig. 5 illustrates the relationship between the serum sampling apparatus and a measurement section for analytically measuring the serum sample. In Fig. 5, numeral 1 denotes a controller for controlling the overall sampling apparatus and having internally a ROM la storing the operating procedure (see the flowchart of Fig. 7) and a RAM 1b used as a working area. Numeral 2 denotes a sampling base having a fixed portion 4 for fixing the blood-collecting tube 20. The sampling base 2 has a holding body 3 for fixedly holding a sampling needle 5 (hollow) having a pointed end for extracting serum from the blood-collecting tube 20, an air needle 6 (the interior of which is hollow) having similarly shaped tip for supplying air from the outside, and a sensor unit 8 equipped with a sensor at its distal end in order to detect a serum separating agent. The holding body 3 is moved up and down by a motor, not shown. Numeral 9 denotes a tube for introducing sampled serum, 10 an electromagnetic valve, 11 a rotary-type pump, and 12 a measurement section for measuring and analyzing sampled serum. Ordinarily, the amount of blood collected inside the blood-collecting tube 20 is substantially constant. Therefore, when the sensor unit 8 senses the serum-separating agent 101, the positional relationship among the components is fixed in advance in such a manner that the tip of the sampling needle 5 will be situated within the serum layer 100 and the air needle 6 is situated in the air space of the blood-collecting tube 20. Numeral 102 denotes a clot layer. The operating process of the serum sampling apparatus in the embodiment thus constructed will now be described in accordance with the flowchart of Fig. 6. It is assumed that the holding body 3 is at the position of the broken line in Fig. 5 before the measurement operation starts. First, when the blood-collecting tube 20 in which the serum layer 100 has been produced by centrifugal separation is secured to the fixed portion 4, the holding body 3 is at rest (step S1) at the position of the broken line in the drawing until a start switch, not shown, is operated. Rather than relying upon a start switch, it is permissible to provide a sensor which senses that the blood-collecting tube 20 has been secured to (or placed on) the fixed portion 4, with sampling being started in response to a signal from this sensor. In any case, when the start of operation has been instructed, the program proceeds to step S2, at which a motor (not shown) is driven to move the holding body 3 downward. During downward movement of the holding body 3, the controller 1 is receiving a signal from the sensor of the sensor unit 8, with downward movement continuing until the serum-separating agent 101 (white in color) is detected (step S3). When a signal is received from the sensor unit 8 indicating that the serum-separating agent has been detected, the holding body is moved by an amount equal to the difference in distance between the sensor unit and the tip of the needle (step S9). The motor is stopped at step S4 to halt movement of the holding body 3. Thereafter, the electromagnetic valve 100 is opened (step S5) and processing for driving the pump is executed (step S6) to supply a predetermined amount of serum to the measurement section 12. This is followed by stopping the pump 11 and the electromagnetic valve 10 (step S7). Now the motor is driven to return the holding body 3 to its starting position, with the motor being stopped when the starting position is attained (step S8). Preparations are then made for the next specimen via a cleansing mechanism. The serum can be divided up without it reaching the measuring device. In accordance with the blood specimen sampling method of the invention as described above, the blood-collecting tube is kept in a closed state from the time blood is collected until the objective blood specimen is sampled from the blood-collecting tube. During this time, therefore, the blood specimen inside the blood-collecting tube will not spill out and foreign matter will not mix in from the outside. Further, in accordance with the blood specimen sampling apparatus of the invention, besides obtaining the foregoing advantages it is also possible to extract the blood component automatically, thereby raising operating efficiency by a wide margin. Furthermore, sampling of serum is facilitated by introducing an air needle into the blood-collecting tube.

Claims: A blood specimen sampling method for sampling a blood specimen from a blood-collecting tube (20) having a film stopper (24) provided to an opening portion thereof, said stopper (24) comprising a gas-barrier film layer (24a) and a rubber layer (24b) for resealing on the gas-barrier film layer (24a), said tube (20) containing a blood specimen including a serum layer (100) and a clot layer (102) separated by a serum-separating agent layer (101), comprising the steps of: introducing a needle (5) having a distal end into the interior of said blood collecting tube (20) by moving downward a holding member (3) which holds said needle (5) and a sensor (8) for detecting said serum-separating agent layer (101) from the outside of the tube (20) at a predetermined position downbelow said distal end of said needle (5); detecting said serum-separating agent layer (101) by said sensor (8) while introducing said needle (5) into the interior of said blood collecting tube (20) by penetrating said film stopper (24) with said distal end of said needle (5); adjusting the position of said distal end of said needle (5) to the predetermined position in said serum-layer (100) by moving said holding member (3) by a distance based on the relative distance between said distal end of said needle (5) and a position of said sensing portion of said sensor (8) after said sensor (8) detects said serum-separating agent layer (101); and drawing a blood specimen into said needle (5) from said distal end portion of said needle (5) from only said serum layer (100). The blood specimen sampling method according to claim 1, characterized by further including a step of piercing said film stopper (24) with an air-introducing needle (6) at least before the blood specimen is drawn in. The blood specimen sampling method according to claim 1 or 2, characterized by said gas-barrier film layer (24a) having a thickness of 10-200 µm and said rubber layer (24b) having a thickness of 0.3-2 mm. A blood specimen sampling apparatus for sampling a blood specimen from a blood-collecting tube (20) having a film stopper (24) provided to an opening portion thereof, said stopper (24) comprising a gas-barrier film layer (24a) and a rubber layer (24b) for resealing on the gas-barrier film layer (24a), said tube (20) containing a blood specimen including a serum layer (100) and a clot layer (102) separated by a serum-separating agent layer (101) comprising: introducing means for introducing a needle (5) having a distal end into the interior of said blood collecting tube (20) by moving downward a holding member (3) which hold said needle (5) and a sensor (8) for detecting said serum-separating agent layer (101) from the outside of the tube (20) at a predetermined position down below said distal end of said needle (5); detecting means for detecting said serum-separating agent layer (101) by said sensor (8) while said introducing means is introducing said needle (5) into the interior of said blood collecting tube (20) by penetrating said film stopper (24) with said distal end of said needle (5); adjusting means for adjusting the position of said distal end of said needle (5) to the predetermined position in said serum-layer (100) by moving said holding member (3) by a distance based on the relative distance between said distal end of said needle (5) and a position of said sensing portion of said sensor (8) after said sensor (8) detects said serum-separating agent (101); drawing means for drawing a blood specimen into said needle (5) from said distal end portion of said needle (5) from only said serum layer (100). The blood specimen sampling apparatus according to claim 4, characterized in that the sampling means includes an air-introducing needle (6) capable of introducing air into the blood-collecting tube (20) from the outside thereof. The blood specimen sampling apparatus according to claim 4 or 5, characterized in that the blood specimen sampled is serum, and the detecting means detects an interface between a blood serum layer (100) and a clot layer (102), penetrating operation of the sampling means being halted based on the results of detection performed by the detecting means. The blood specimen sampling apparatus according to claim 6, characterized in that the detecting means detects blood serum separating means situated at the interface between the blood serum layer (100) and the clot layer (102) in the blood collecting tube (20). The blood specimen sampling apparatus according to any one of claims 4 to 7, characterized by said gas-barrier film layer (24a) having a thickness of 10-200 µm and said rubber layer (24b) having a thickness of 0.3-2 mm.

Inventors: KASAI MASAAKI, YAMAZAKI SAKAE, KASAI, MASAAKI, YAMAZAKI, SAKAE
Applicants: TERUMO CORP, TERUMO KABUSHIKI KAISHA
Application year: 1988
Main classification: G01N1
IPC codes: G01N1, A61B5