A DEVICE FOR RAPIDLY PERFORMING A SEDIMENTATION-RATE TEST

Abstract: A device for rapidly performing a sedimentation-rate test is described. A tube (17) containing a given amount of blood specimen is placed in a holder (13, 21, 22) which rotates (23) the tube (17) a predetermined number of revolutions at a given speed about an axis perpendicular to the longitudinal axis of the tube while rotating (24) the tube about its longitudinal axis, to then stop the tube for a given period of time about 60 DEG from the vertical, and to finally turn the tube (17) to the vertical position at a speed which is but a fraction of the first-mentioned speed also while turning the tube about the longitudinal axis. Means (26) are arranged to monitor the rotational movements of the tube, preferably by means of markings on a plug (18) closing the tube end.

Description: A_DEVICE FOR RAPIDLY PERFORMING A SEDIMENTATION-RATE TEST The present invention relates to a device for rapidly performing a sedimentation-rate test, comprising an elon- gate lid-equipped vessel for receiving a given amount of blood, and a frame with a holder for said vessel which, when disposed in the frame, is rotatable in the vertical plane about an axis perpendicular to its longitudinal axis, and rotatable about its longitudinal axis. The sedimentation-rate test is a blood test commonly used in medical check-ups. It is a non-specific test, but gives, when combined with other tests, an idea of e.g. on¬ going inflammatory processes. Today, the sedimentation-rate test is standardised by national and international organisations, such as the NCCLS, the ICSH and the WHO. In most cases, it is perform¬ ed by letting a tube (vessel), which has a length of about 250 mm and an inner diameter of about 2.54 mm, be filled with a mixture of citrate and blood at room temperature to a height of 200 mm, and placing the tube in the vertical position for 60 min. Then, the sedimentation-rate is read as the decrease in height (mm) of the red blood column compared with the original height. The overall testing time is about 70-75 min, including the cooling of the blood to room temperature. The blood used in the sedimen¬ tation-rate test may be either venous or capillary blood. Stein W: 'Blutsenkungen in 10 Minuten-Verfahren' Med. Mschr 1949, 3, pp 919-921 describes a quick sedimentation- rate test of common type used. In this method, the sedi- mentation tube is placed at an angle of 60° to the verti¬ cal, and the sedimentation-rate value in mm/h can be read after 10 min. However, this method requires reading ex¬ perience, and is not widely used. Norwegian Patent 153,508 discloses a modified version of the quick sedimentation- rate test according to Stein. In the Norwegian method, which is used for simplifying the reading of a tilted sedimentation tube, the tube is, while turned a certain number.of revolutions, erected to the vertical position where a conventional reading is performed. When testing venous blood of which a few millimetres are available, a specimen is taken by means of a syringe, often filled with a suitable quantity of citrate, or a vacuum tube filled beforehand with citrate. The vacuum tube is highly advantageous in terms of hygiene, since th blood and the citrate thus are mixed in a tube where the proportion of blood to citrate is ensured by the vacuum present in the tube when the blood specimen is taken. In standardised sedimentation tube design, the tube (vessel) is then filled with the solution of citrate and blood, as described earlier. In cases where the sedimentation rate is read directly from a vacuum tube with an inner diamete exceeding 3 mm, the vacuum tube is placed in the vertical position, and after the solution has been brought to room temperature with intense mixing in the vertical position, the sedimentation rate is read after 60 min in the manner described. When the sedimentation rate is read directly from short vacuum tubes in which the height of the blood column is less than 200 mm, a conversion scale is employ¬ ed to give a sedimentation-rate numerical value equivalen to that obtained by the standardised method. In an articl by B. Hjalmarsson, published in Laboratoriet No. 6/85, a vacuum-tube system for sedimentation-rate tests is de¬ scribed, which employs a tube with an inner diameter of 9 mm. It appears from this article that the analysis takes at least 70 min when a vacuum tube is used, including the time required for mixing and bringing the solution to roo temperature. If capillary blood, e.g. taken from the fingertips, is used, only small quantities of blood are available. A special method is required when the capillary blood is diluted with a quantity of citrate corresponding to a dilution ratio of blood to citrate of 1/41, and the citrated blood is agitated and drawn up in a tube with a total volume which usually is less than 150 μl. The inner diameter of a suitable tube then is in the order of 1 mm. One object of the present invention is to provide a device for implementing the method of Norwegian Patent 153,508 and, in addition, to reduce the time required for the analysis by making provisions for a mixing operation before the analysis. Another object of the invention is to provide a vessel, preferably a vacuum tube, which is to be used in the device to enable hygienic handling and mini¬ mise the risk of the device being contaminated. A further object of the invention is to provide means for verifying that the tube has performed certain movements. The objects of the invention are achieved by the device set forth in the appended claims. The invention will be described in more detail below with reference to the accompanying drawings, in which Fig. 1 schematically illustrates an embodiment, and Fig. 2 is a graphic comparison between the device of the invention and a prior-art device. Fig. 1 is a front view of a device for rapidly per- forming a sedimentation-rate test, which consists of a frame in the form of a closed housing 10, preferably of plastic. The housing 10, which is intended to be placed on a table, has a vertical front 11 which is formed with a circular through opening 12 in which a circular disc 13 is rotatably mounted. Around the opening is provided an annu¬ lar ridge, or flange 14 which may be integrally formed with the front 11 of the housing 10 or consist of a ring non- rotatably fixed in the opening. The disc 13 is rotated in the opening 12 by a motor 15 (indicated by broken lines) through a transmission (indicated by dash-dot lines). The motor 15, which preferably is a step motor, can be accu¬ rately controlled as to the speed of rotation. To perform the sedimentation-rate test, use is made of a vessel for receiving the blood specimen. The vessel preferably is a tube 17 whose ends are closed, one perma¬ nently and the other by a plug generally designated 18. The plug 18 is made of rubber or plastic, or a combination of the two, and has, as shown in Fig. 1, a lower cylin¬ drical part 19 sealingly applied to the tube wall, and an upper cylindrical part 20 having a slightly larger diame¬ ter than the lower part 19. The plug is so designed that cannula can be run therethrough from the end surface to supply the blood specimen, and when the cannula is then withdrawn, the supply opening closes automatically. A tub of this type suitably has such a length that the height o the blood column can be at least 100 mm, and is delivered filled with citrate solution. Although different sorts of tubes can be used, a vacuum tube is especially suitable. vacuum tube is a tube from which the air has been evacuat ed before the insertion of the plug, to give a certain negative pressure in the tube. In the taking of specimens, a vacuum tube is automatically filled with a given quan¬ tity of blood when the negative pressure in the tube returns to normal, i.e. to the ambient pressure. To perform the quick sedimentation- ate test, the tube is placed on the end surface of the disc 13 facing away from the housing 10, with the aid of a bearing means 21, in which the end of the tube 17 remote from the plug 18 is rotatably mounted, and an additional bearing means 22 through which the tube 17 can be passed and which also permits rotation of the tube 17. The bearing means 21 is arranged at some distance from the centre of the disc 13, and the bearing means 22 is, as can be seen in Fig. 1, aligned with the bearing means 21 and located on the same diameter. The distance between the centre of the disc 13 and the bearing means 21 is such that the cylindrical part 19 of the plug 18 for the tube 17 will be pressed against the flange 14 with a predetermined friction when the tube is placed in the two bearing means. When the disc 13 is rotated by the motor 15 and the transmission 16, and the tube 17 rotatably mounted on the disc by the bearing means 21 and 22 is rotated about an axis perpendicular to the longitudinal axis of the tube, the tube 17 will also ro¬ tate about its longitudinal axis, as indicated by an arrow 24, owing to the engagement between the flange 14 and the plug 18. Thus, the tube 17 is rotated about the axis per¬ pendicular to the longitudinal axis of the tube in the vertical plane by means of the motor 15 and the trans- mission 16, as indicated by an arrow 23, and at the same time about its longitudinal axis, as indicated by the arrow 24. When performing the sedimentation-rate test, it is essential that these rotational movements are as accu¬ rate as possible, for which reason a processor 25 is pro- vided in the housing 10. Further, means are arranged for monitoring the rotational movements. These means may be of electric or magnetic type, but preferably consist of an optical transducer 26 arranged in a projecting part of the front 11 of the housing 10, opposite to the path of move- ment of the rotating tube 17, as illustrated in Fig. 1. When the plug passes, the optical transducer 26 scans for a suitable marking on the end surface of the plug portion 20 facing the transducer. However, this marking need not be provided on the end surface, but may be placed else- where on the plug 18 or on the tube 17 itself, in which case the transducer 26 naturally has to be arranged other¬ wise than in Fig. 1. As indicated at 27, signal lamps and switches may also be provided on the housing 10. The motor 15, the transducer 26 and the signal lamps and switches at 27 are, of course, connected to the processor 25 by lines not shown in Fig. 1. When performing a sedimentation-rate test, the blood specimen is first injected into the tube 17 by means of a suitable cannula, or the tube is automatically filled if being a vacuum tube. The tube 17, already containing a citrate solution, is then placed in the bearing means 22 and 21 with the plug portion 19 contacting the flange 14. The motor 15 is then started by means of a switch, and the tube 17 is rotated a predetermined number of revolutions for a given time in the vertical plane in the direction indicated by the arrow 23. Thereafter, the motor 15 is stopped in a position in which the tube 17 is about 60° from the vertical, as indicated by double-dotted-dash lines. The tube 17 is maintained in this position for a given period of time, whereupon the motor 15 is again started and moves the tube from the 60"-position to an erect position, i.e. along the vertical. The tube 17 is moved to the vertical position at a speed which is but a fraction of the first-mentioned speed. In practice, a tub 17 with an inner diameter of 6 mm may first be rotated through 8 5/6 revolutions in the direction indicated by the arrow 23 and through 106 revolutions in the direction indicated by the arrow 24 in the course of about 3 min, t be subsequently maintained stationary in the position about 60° from the vertical for about 9 min, and finally be turned from the 60"-position to the vertical position in the course of 10 min, the tube 17 rotating two revolu¬ tions about its longitudinal axis. When the tube 17 after these movements has been plac ed along the vertical, the sedimentation-rate is measured which may be carried out by a scale fixedly or adjustably arranged on the disc 13 or by a loose scale. The device described above and illustrated in Fig. 1 is very easy to handle and advantageous also from the poi of view of hygiene. However, it goes without saying that the device may be designed in many other ways, provided that the tube 17 moves about and perpendicular to its longitudinal axis for given periods of time, as stated. The device according to the invention was used in a study aiming at comparing the quick sedimentation-rate te of the invention with a vacuum tube commercially availabl for this purpose, Seditainer ®, Becton Dickison, Rutherfor New Jersey, USA. The study bore upon 153 specimens. One ® blood specimen was taken with Seditainer and one was tak with the tube according to the invention. The results are shown in Fig. 2. As is apparent, a correlation factor of 0.98 and a regression line y = 0.92 x +5 were obtained. Thus, the device according to the invention is well up to the standard of a commercially available method.

Claims: CLAIMS 1. Device for rapidly performing a sedimentation-rate test, comprising an elongate, lid-equipped vessel (17) for receiving a given amount of blood, and a frame (10) with a holder (13, 21, 22) for said vessel which, when disposed in the frame, is rotatable (23) in the vertical plane about an axis perpendicular to its longitudinal axis, and rotatable (24) about its longitudinal axis, c h a r a c t e r i s ¬ e d in that the holder is adapted to rotate the vessel (17) a predetermined number of revolutions at a given speed about the axis perpendicular to the longitudinal axis, while simultaneously turning the vessel about its longitudinal axis, and then stop the vessel in a position in which its longitudinal axis forms a predetermined angle with the vertical for a given period of time, to subsequently turn the vessel about the first-mentioned axis from said angled position to the vertical position and the sedimentation-rate-measuring site at a speed which is but a fraction of the first-mentioned speed also while turning the vessel about the longitudinal axis. 2. The device of ' claim 1, c h a r a c t e r i s e d in that electric, magnetic or optical means (26) are arranged to monitor the rotational movements of the vessel (17) by means of markings preferably provided on the lid (19, 20) of the vessel. 3. The device of claim 1 or 2, wherein the vessel (17) is a tube, preferably a vacuum tube, whose one end is closed by a pierceable, self-sealing cylindrical plug (18), c h a r a c t e r i s e d in that the frame (10) has a holder (13,- 21, 22) which is surrounded by a circular ring (14), said tube being so positionable in the holder (13, 21, 22) that the cylindrical surface of the plug (18) is applied against the ring (14), such that the tube, while rotating about the axis perpendicular to the longitudinal axis, is rotated about the longitudinal axis owing to the engagement between the plug (18) and the ring (14). 4. The device of claim 3, c h a r a c t e r i s e d in that the holder (13, 21, 22) comprises a circular, fla disc (13) which, on the side facing outwards and away fro the frame (10), has a bearing means (21) for the tube end opposite to the end closed by the plug, said bearing mean being arranged on a diameter of the disc (13) at a distan from the centre of the disc, and another bearing means (2 arranged on the diameter close to the periphery of the disc. 5. The device of any one of claims 2, 3 and 4, c h a r a c t e r i s e d in that the means (26) for monitoring the operation of the vessel (17) is an optical transducer arranged diametrically outside the path of movement of the vessel (17) and adapted to sense a marking on the end surface of the plug (18). 6. The device of any one of the preceding claims, c h a r a c t e r i s e d in that the holder (13, 21, 22) is rotated by a step motor (15) which is controlled by a processor (25) also connected to said monitoring means (26). 7. The device of any one of the preceding claims, c h a r a c t e r i s e d in that the vessel (17) is a tube with an inner diameter of about 6 mm, and that the holder (13, 21, 22) is adapted to rotate the tube through 5/6 revolutions in the course of about 3 min about the axi perpendicular to the longitudinal axis while rotating the tube through 106 revolutions about the longitudinal axis, to keep the tube stationary in a position about 60° from the vertical for about 9 min, and to finally turn the tube through the remaining about 60° to the vertical position and through 2 revolutions about the longitudinal axis in the course of about 10 min.

Inventors: LILJA JAN EVERT, NILSSON SVEN-ERIK, LILJA, JAN, EVERT, NILSSON, SVEN-ERIK
Applicants: HEMOCUE AB
Application year: 1991
Main classification: G01N15
IPC codes: B04B5, G01N15