Analysis system for analyzing a sample on a test element

The invention relates to an analysis system for analyzing a sample on a test element. The system has an analysis unit for generating a signal as a function of an analyte contained in a sample, and a detection unit for detecting the signal. The analysis system further includes a test element holder into which the test element can be reversibly introduced and in which it can be positioned relative to the analysis unit and the detection unit. The test element contains at least one guide element, which is suitable for laterally guiding the test element, so that the test element in the test element holder is held and guided only on an outer region of the test element, and an inner region of the test element introduced into the test element holder remains free. The test element contains a sample application site in the inner region.

The present application claims priority to German Patent Application No. 10 2004 036 474.5, filed on Jul. 28, 2004, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an analysis system for analyzing a sample on a test element.

BACKGROUND

In order to analyse samples, for example bodily fluids such as blood or urine, it is common to use analysis systems in which the samples to be analyzed are located on a test element, and optionally interact in a test field with one or more reagents on the test element before they are analyzed. The optical, in particular photometric, evaluation of test elements is one of the most commonly used methods for rapidly determining the concentration of analytes in samples. Photometric evaluations are widely used in the field of analysis, environmental analysis and above all in the field of medical diagnosis. Especially in the field of blood glucose diagnosis from capillary blood, test elements which are photometrically evaluated are of great value.

There are various forms of test elements. Essentially square sheets, also referred to as slides, in the middle of which there is a multilayer test field are known, for example. Diagnostic test elements which are of strip-shaped design are referred to as test strips. Test elements are described in the prior art, for example in the documents DE-A 197 53 847, EP-A 0 821 233, EP-A 0 821 234 or WO 97/02487. The present invention relates to test elements of any shape, and in particular strip-shaped elements.

Test elements in which a sample is applied to a sample application site, and is transported by means of capillary action to a detection zone (test field) separate from the sample application site, are known in the prior art. For example, DE 197 53 847 A1, published in English as CA2311496, which is hereby incorporated by reference in its entirety relates to such a test element. It describes an analytical test element for the determination of an analyte in a liquid. It contains an inert support, a detection element and a channel suitable for capillary liquid transport, which has a sample application opening at one end and a ventilation opening at the other end of the channel suitable for capillary liquid transport. The channel suitable for capillary liquid transport is formed at least partially by the support and the detection element, and extends in the capillary transport direction from the sample application opening at least as far as the detection element edge closest to the ventilation opening, a recess in a face which forms the channel suitable for capillary liquid transport being located on the test element edge forming the sample application element. The test element edge forming the sample application opening is thus interrupted at least partially on one side, and the face opposite the recess is free. The recess in a face forming the capillary channel on the edge of the test element is used to ensure that the sample liquid can enter the capillary channel. This is achieved in that the sample drop on the test element edge closest to the sample application opening, which is interrupted by the recess, can be brought directly in contact with one of the faces which form the inner surface of the capillary in their extension. By suitable choice of the geometry and dimensions of the recess, the liquid drop is very likely to come in contact with the active capillary zone and be readily sucked into the interior of the capillary, regardless of the exact position of the dosing.

For the analytical study of a sample on a test element, test element analysis systems are known in the prior art which contain a test element to position the test element in a measuring position, and a measurement and evaluation device for carrying out a measurement and determining an analysis result based on this. WO 00/19185 A1, which is hereby incorporated by reference in its entirety, relates to a device for the photometric evaluation of test elements, containingan illumination unit having at least a first light source and a second light source,a frame for receiving a test element with a detection zone, so that the detection zone is positioned opposite the illumination unit,a detection unit having at least one detector, which detects light reflected by the detection zone or transmitted through the detection zone,a control unit, which activates the two light sources and records the signal generated by the detection unit as a detection signal, andan evaluation unit, which evaluates the detection signals in order to determine the analyte concentration contained in the sample.

Known types of measuring apparatus have an opening, generally a slot, into which the test elements can be inserted. Guide elements ensure that a test element is inserted with the intended orientation. If the test element is introduced manually into the apparatus, design features of the apparatus must be provided which guarantee the desired positioning of the test element. This is usually done by a restriction which prevents insertion beyond a predetermined target position. Analysis systems which contain a storage container (magazine) with a multiplicity of test elements are furthermore known in the prior art. In this case, for example, a test element is transported from the storage container to the measuring position by a slide or plunger, and is automatically discarded from the analysis system after the measurement has been carried out.

DE 199 02 601 A1, published in English as U.S. Pat. No. 6,475,436 (B1), discloses a device for extracting a consumable analytical medium, in particular a test element, from a storage container which has one or more chambers containing consumable media. The chambers respectively have an extraction opening for extracting a consumable medium and an insertion opening, opposite the extraction opening, for introducing a plunger to transport the consumable medium. The extraction opening and the insertion opening are closed by a film in order to store the consumable medium. The device comprises a plunger which can be moved by means of a drive unit in order to extract a consumable medium.

Discarding the consumable test elements entails a contamination or infection risk since they are released without control into the environment and carry the rest of the sample material (for example blood, urine or interstitial fluid) on their surface. Hygienic handling and disposal of the test elements could be ensured by transport back into a storage magazine contained in the analysis system being used (re-magazining) or transport into a waste magazine intended for disposal of the test elements.

In the test element analysis systems known in the prior art, the test element in the measuring position rests via at least a large fraction of its lower side on a measuring apparatus surface in the analysis system. The lower side is pushed over the measuring apparatus surface during transport of the test element into and out of the measuring position. The test element is in this case guided by means of lateral guide faces which are perpendicular to the measuring apparatus surface. In a system for photometrically evaluating the test element, the measuring apparatus surface usually contains an optical window, below which the optics are located. Resting the test element via a large fraction of its lower side on the measuring apparatus surface has the disadvantage that a liquid sample applied to the test element, in the vicinity of one of its side edges, can stain the measuring apparatus surface. For example, a part of the liquid sample could be drawn by capillary forces between the test element and the measuring apparatus surface, so that a further region including the optical window is wetted with the sample. Such staining occurs in particular when the test element is being drawn back over the measuring apparatus surface into the magazine after the measurement has been carried out (re-magazining). In this case, any sample adhering to the test element edge used for the sample application will be wiped over the measuring apparatus surface.

The optical window of the analysis systems known in the prior art has to be sunk into the measuring apparatus surface in order to protect it against damage due to friction by the test element.

SUMMARY

The analysis system of the present invention comprises an analysis unit for generating a signal as a function of an analyte contained in a sample, and a detection unit for detecting the signal, and a test element holder into which the test element can be reversibly introduced and in which it can be positioned relative to the analysis unit and the detection unit. The test element contains at least one guide element which is suitable for laterally guiding the test element, so that the test element in the test element holder is held and guided only on an outer region of the test element, and an inner region of the test element introduced into the test element holder remains free. The test element contains a sample application site in the inner region.

Further, a method of analyzing the glucose content in a sample is provided in accordance with the invention. The method comprises the steps of providing a test element having an outer region and an inner region, the inner region containing a sample application site, providing an analysis system comprising an analysis unit for generating a signal as a function of glucose contained in the sample, a detection unit for detecting the signal, and a test element holder into which the test element can be reversibly introduced and in which the test element can be positioned relative to the analysis unit and the detection unit, the test element holder containing at least one guide element which is suitable for laterally guiding the test element, so that the test element in the test element holder is held and guided only on the outer region of the test element, and the inner region of the test element introduced into the test element holder remains free, applying a sample to the sample application site of test element, introducing the test strip into the test element holder so that the test element is held on the outer region, generating a signal as a function of the glucose contained in the sample, and detecting the signal.

Still further, an apparatus for holding a test element used in an analysis system is provided. The test element has an outer region and an inner region, the inner region containing a sample application site. The apparatus comprises a body being formed to include a guide element sized for laterally guiding the test element so that the test element in the body is held and guided only on the outer region of the test element, and the inner region of the test element introduced into the test element holder remains free, the guide element including spaced-apart support faces, on which the test element rests in its outer regions, and an optical window spaced-apart from the guide element.

In an embodiment of the invention, the analysis unit and the detection unit can be parts of measuring optics, which are used to photometrically evaluate the test element. A light source and optics are for example used as the analysis unit for photoelectric evaluation, and for example a photodetector which detects the light reflected by the test field supplied with the sample or transmitted through the test field (optical signal) is used as the detection unit. Such a detection signal is evaluated in the known way in order to determine the analyte concentration.

In an embodiment of the present invention, the guide element contains support faces, on which the test element rests via bearing faces in its outer region, and guide faces along which side faces of the test element are guided. In this context, care should be taken that sufficient clearance still remains between the slue faces of the test element and the guide faces, so that the test element can be moved in the guide element with minimal force exertion and so as to maintain a low level of wear (for example, abrasion of the test element or notching in the guide walls).

In an embodiment of the present invention, the guide faces are arranged obliquely with respect to the side faces of the test element. The effect achieved by this is that a test element does not touch the guide faces over the entire side faces when it is being introduced into the guide element, but is displaced along the guide faces via one edge. This is particularly for test elements which are made of different layers adhesively bonded together. Such a test element is described, for example, in DE 199 12 365 A1 published in English as U.S. Pat. No. 6,881,378 (B1), which is hereby incorporated by reference in its entirety. Because of the obliquity of the guide faces, they are not stained by any adhesive which may be encountered on the side faces of the test element.

The bearing faces on which the test element rests in its outer region have a width of from 0.1 mm to 1 mm, particularly from 0.3 mm to 0.5 mm. With a correspondingly small clearance, they are therefore wide enough to prevent the test element from undesirably falling out of the guide element.

In an embodiment of the present invention, the guide element contains two mutually opposite grooves, into which the test element can be inserted via its outer region. In such a guide element, the test element is introduced by a sliding movement into two grooves, one each on the left-hand and right-hand sides of the test element. The grooves enclose the edges and side faces of the test element so that the test element cannot fall out of the guide element neither upwards nor downwards (closed guiding).

In an embodiment of the present invention, the guide element is arranged above the analysis unit and/or the detection unit in the analysis system. For the photometric evaluation, for example, the measuring optics (including the light source and photodetector) are arranged at a slight distance below the guide element in the analysis system. It is nevertheless possible to arrange the analysis unit above the guide element and the detection unit below the guide element, or vice versa.

In an embodiment of an analysis system according to the invention, the guide element is arranged so that a test element introduced into the guide element is at a distance of at least 1 mm from the analysis unit and the detection unit in any position. This distance ensures that the liquid sample cannot be drawn in by capillary forces between the test element and the analysis unit or the detection unit, and stain it. Furthermore, for example, an optical window no longer has to be sunk into the measuring apparatus surface since the distance protects it from mechanical stress, which simplifies the design of the analysis system.

In an embodiment of the present invention, the test element holder contains a stop, against which a test element abuts when it is being introduced into the guide element, so that a defined position of the test element in the test element holder is achieved. The stop establishes how far the test element should be introduced into the guide element.

In an embodiment of the present invention, the test element comprises a sample application site at one end in the inner region, the test element being tapered in the region of the sample application site. The tapering may, for example, be in the form of a shoulder or indentation. This test element can be wetted with the sample only over the width of the tapered end in its inner region, and not over the full width. The outer region of the test element, in which it is held and guided, thus remains free of the sample, and staining of the guide element which is in contact with the outer region is substantially avoided. The tapered region of the test element, with the sample application site, may furthermore protrude out of the test element holder in order to allow sample application on the outside. In particular, the guide element may have a stop on which the wide (normal) region of the test element, which is next to the tapered region, abuts as soon as it has been introduced over a sufficient distance into the guide element.

In an embodiment of the present invention, the analysis system also comprises a storage container for a multiplicity of test elements, into which the test elements are transported back from the test element holder after use. As such, the used test elements are handled and disposed of hygienically. The analysis system according to the invention in this case has a transport device for automatically extracting a test element from the storage container, for automatically transporting the test element into the test element holder and for automatically transporting the test element back into the storage container after use. The transport device comprises, for example, a plunger, a hook or a clip, which can couple to a test element and subsequently transport it into a desired position in the analysis system. In an embodiment of the present invention, the test element has a test field where the sample is analyzed, and which is positioned in the inner region of the test element. For the qualitative or quantitative analytical determination of components of the liquid sample, in particular bodily fluids, reagents are embedded in the test field. The test field is brought in contact with the sample and, if a target analyte is present, the reaction between the liquid sample and the reagents leads to a detectable signal, for example a colour change, which can be detected with the aid of the analysis unit and the detection unit. In the present invention, the test element contains a capillary for delivering the sample to the test field.

In one embodiment of the present invention, the test element holder is made of at least two parts, with a test element introduced into the test element holder resting in its outer region on a lower part of the test element holder and with a separate upper part of the test element holder resting on the test element in its outer region. In the absence of a test element, the two parts are placed loosely on one another and are laterally secured against displacement. When a test element is introduced into the guide element between the two parts of the test element holder, the two parts are pressed apart from each other by the test element. The test element therefore fits tightly into the guide element and is held in position by the upper part, which rests on its outer region, for example when the sample application and/or measuring position has been reached.

At least one pressure spring, which exerts a force on the upper part in the direction of the lower part of the test element holder, is arranged on the upper part of the test element holder. The spring force additionally holds the test element in position.

In the present invention, the guide element may have a ramp- or funnel-shaped introduction opening on the side where a test element is introduced into the test element holder. The ramp- or funnel-shaped introduction opening facilitates the introduction of a test element into the guide element.

In one embodiment of the present invention, the guide element is shaped so that it causes a defined deformation of a test element introduced into the test element holder, in order to fix it during use. For example, the guide element may be bent in the longitudinal direction so that a test element is deformed in a defined way in the longitudinal direction when it is being introduced into the guide element, and is under a flexural stress in the measuring position. This ensures the defined distance of the test field from the measurement unit comprising the analysis unit and the detection unit. Likewise, for example, the guide element designed as two grooves may be inclined with respect to the introduction plane of the test element so that the test element in the guide element is deformed in a defined way in the transverse direction. This likewise fixes the test element in the test element holder.

These and other features of the present invention will be more fully understood from the following detailed description of the invention taken together with the accompanying claims. It is noted that the scope of the claims is defined by the recitations therein and not by the specific discussion of the features set forth in the present description.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1Aschematically shows the introduction of a test element into a guide element of an analysis system in the prior art.

In this case, the guide element1is a sort of open trough with a bearing face2and side walls3. In the bearing face2, there is an optical window4(symbolized by the circle) below which measuring optics (not shown) are arranged for photometrically evaluating the test element5. A test element5is introduced into the guide element1in the introduction direction6, while sliding with its full width via its lower side7over the bearing face2. It is guided during introduction by the side walls3, along which the side faces11of the test element5slide. In the sample application position8, the test element5rests extensively on the bearing face2. The test element5protrudes beyond the bearing face2via its end9, which contains the sample application site10.

This design of the guide element1as represented inFIG. 1A, in which the test element5guided only laterally rests flat via the lower side7, is configured so that after the measurement (and the sample application associated with it) the test element is not guided through the guide element1via the end to which the sample has been applied. This movement does, however, take place in an analysis system with a re-magazining function. This will be demonstrated inFIGS. 1B and 1C.

FIG. 1Bshows the sample application on a test element in a guide element of an analysis system in the prior art.

The test element5is displaced into the sample application position8while being guided by the guide element1, as represented inFIG. 1A. In order to apply the sample12, for example blood, the test element5protrudes slightly from the analysis system in this position. A sample12is applied onto the test element5at the sample application site10. For this, the end9of the test element5is dipped slightly into the sample12so that it is wetted with the liquid sample12on its upper side13and its lower side7.

FIG. 1Cshows the extraction of a test element after a measurement from a guide element of an analysis system in the prior art.

If, after the measurement, the test element5is drawn back counter to the introduction direction6(for example to re-magazine the test element5) from the sample application position8through the guide element1, then drops of the sample12adhering to the end9of the test element5will be wiped off on the edge14of the guide element1. By capillary forces, sample material will be drawn into the gap between the test element5and the bearing face2, and will be further distributed over the bearing face2by the extraction of the test element5over it. This leads to contamination or staining15of a wide region of the bearing face2, including the optical window4, by the sample material. The optical window4of the guide element1of an analysis system in the prior art, as shown inFIGS. 1A to 1C, needs to be sunk into the bearing face2for the test element5, in order to protect it against damage due to friction by the test element5during the introduction and the extraction of the test element5from the guide element1.

FIGS. 2A and 2Bdemonstrate how test elements in the prior art are handled manually or automatically.FIG. 2Ashows the manual handling procedure for a test element in an analysis system of the prior art.

In manually operated analysis systems, the test element5is pushed into the analysis system by the user in the introduction direction6, into the guide element1and over the optical window4. In the sample application position8, a sample12is put onto the sample application site10and the measurement is subsequently carried out. After the measurement, the test element5is extracted from the analysis system by the operator. The extraction is carried out in the extraction direction16, which is opposite to the introduction direction6. The edge17of the test element5, which is wetted with the sample12, thus never touches the bearing face2and the optical window4, so that staining is avoided. With such an analysis system in the prior art, extraction in the same direction as the introduction direction6is not intended and would lead to staining of the bearing face2, as described with reference toFIG. 1C.

FIG. 2Bshows the automatic transport procedure for a test element in an analysis system of the prior art.

In automatically operated analysis systems of the prior art, the test element5is pushed from a storage magazine18(for example by a plunger, not shown) in the introduction direction6into the guide element1. In the sample application position8, a sample12is applied to the test element5at the sample application site10, and a measurement is carried out. After the measurement, the test element5is ejected (for example by the plunger) from the guide element1in the same direction as the introduction direction6. The edge17of the test element5, which is wetted with the sample12, therefore does not touch the bearing face2or the optical window4, so that staining by the sample12is avoided. With such an analysis system in the prior art, extraction of the test element after the measurement in the opposite direction to the introduction direction6(for example to put it back into the storage magazine18) is not intended and would lead to staining of the bearing face2, as described with reference toFIG. 1C.

FIG. 3Ashows the schematic representation of a detail of an analysis system according to the invention, into which a test element is introduced. The analysis system of the present invention is intended to avoid staining of surfaces in the analysis system by the sample when a test element is being re-magazined after the measurement. The invention furthermore relates to the use of the analysis so that a test element introduced into the guide element will be positioned relative to the analysis unit and the detection unit. Precise positioning of the test field relative to the measuring optics is necessary in order to be able to carry out an exact photometric evaluation, for example. As shown inFIG. 7, the analysis unit52and the detection unit54are arranged in the analysis system50. They are arranged e.g. below the optical window4, which is shown inFIG. 3A.

In an embodiment of the present invention, the test element holder fulfils not only the function of guiding a test element as it is introduced, but also of holding it so that it remains in the measuring position during the measurement. The test element can be introduced reversibly into the test element holder, so that it can be removed from the test element holder after the measurement in the opposite direction to the introduction direction.

The test elements used in the analysis system according to the invention can be test strips in which a liquid sample, in particular blood, urine or interstitial fluid, is transported from the sample application site to the test field by means of capillary action. A channel suitable for capillary liquid transport usually has an entry opening and a ventilation opening. In an embodiment of the present invention, the entry opening is arranged in the vicinity of the sample application site, i.e. in the inner region of the test element. The ventilation opening in the present invention is likewise arranged in the inner region of the test element, so that any sample liquid accidentally emerging from the ventilation opening cannot cause contamination of the test element holder according to the invention.

The test element5is introduced into the guide element20in the introduction direction6. The guide element20is arranged above the optical window4covering the analysis and detection units in the analysis system. A test element5introduced into the guide element20is at a distance of at least 1 mm from the analysis unit and the detection unit in any position. This distance ensures that no sample material can be drawn from the sample application site10of the test element5by capillary forces into the gap between the test element5and the optical window4. system according to the invention for analyzing the glucose content in blood on a strip-shaped test element.

The analysis system according to the invention contains an analysis unit and a detection unit for photometric analysis, both of which are arranged (this cannot be seen inFIG. 3A, but can be seen diagrammatically, a non-limiting example of which is shown as analysis unit52and detection unit54inFIG. 7) below an optical window4. The analysis system comprises a test element holder19into which the test element5can be reversibly introduced, and in which it can be positioned relative to the analysis and detection units arranged below the optical window4. The test element19contains a guide element20which is suitable for laterally guiding the test element5. The guide element20comprises two mutually opposite grooves21,22, into which the test element5can be inserted in its outer region23. The test element5is then held and guided in the test element holder19only in its outer region23, and an inner region24of the test element5introduced into the test element holder19remains free. The first and second grooves21,22enclose the outer region23of the test element5which has been introduced, so that it cannot fall out of the guide element20either upwards or downwards (closed guiding). The guide element20has support faces25, on which the test element5can rest via bearing faces in its outer region23, and guide faces26along which the test element5is guided during transport. During introduction, enough clearance is left around the outer region23of the test element5so that the test element5can be moved with minor force exertion in the guide element20, and so as to maintain a low level of wear both for the test element5and for the guide element20. The support faces25have a width b of between 0.1 mm and 1 mm.

Staining of the analysis system by the sample is avoided in the present invention since the test element is guided and held only in an outer region, and an inner region of the test element introduced into the test element holder remains free. In this context, the term inner region is particularly intended to mean the central part of the two surfaces of the test element. The sample application site, where the sample is put onto the test element, is located in the inner region of the test element so that it does not come in contact with the test element holder and cannot become contaminated by the sample. The guide element is arranged in the analysis system

The test element holder19may contain a stop (not shown). For example, one end27of the grooves21,22may be closed and thus act as a stop. When inserted into the guide element20, a test element5then abuts against the stop as soon as it has reached its sample application position. Such a stop may also be used for test elements5which are intended to protrude from the analysis system for the sample application if the test elements5have a corresponding shape, in particular if they are tapered in the region of the sample application site, for example in the form of a shoulder or an indentation. The guide element20may furthermore contain position switches (not shown) which allow the test element5to be positioned accurately.

In the test element holder19, the guide element20may be configured so that the test element5is fixed in particular positions by friction or by integrated holding clips or pressure springs (not shown), especially in the sample application or measuring position. Alternatively or in addition, it is possible to fix the test element5with the aid of the drive element (plunger, hook, clip, etc.) which is used for transporting the test element5automatically into the analysis system according to the invention.

FIG. 3Bshows the sample application on a test element in a guide element of an analysis system according to the invention.

The test element is located in the sample application position8, where the sample12is put onto the sample application site10of the test element5. The subsequent measurement may likewise take place in the sample application position8, or it may be carried out in a special measuring position in the analysis system.

FIG. 3Cshows the extraction of a test element after a measurement from a guide element of an analysis system according to the invention.

After the measurement procedure, the test element5is extracted from the test element holder19through the guide element20, and optionally stored (re-magazining) in a storage magazine (not shown). The inner region24of the test element5, which is wetted with the sample material in the vicinity of the sample application site10, is in this case guided through the test element holder at a secure distance from the optical window4and the grooves21,22. Surplus sample material, which would cause staining of the interior of the analysis system, cannot therefore become wiped off. The optical window4is furthermore not mechanically stressed by the test element as it is being displaced, so that it does not have to be sunk and the design of the analysis system is thereby simplified. The measuring optics present below the optical window4are adapted in terms of their distance from the test element5.

FIG. 4shows a test element with tapering in the region of the sample application site.

As a further measure against wetting of the test element5by the sample12over its full width, and against possible concomitant staining of the guide element of the analysis system according to the invention by the sample material, the test element is tapered at one end28in the region of the sample application site10. The tapering29has the shape of an indentation which is selected so that with maximum spreading of the sample12, the wide region30of the test element5is not wetted by the sample12. This prevents pollution of the guide element20, which comes in contact only with the outer region23of the test element5.

FIG. 5shows a multi-part test element holder19with pressure springs in an analysis system according to the invention.

The test element holder19comprises a lower part31and an upper part32, which lie on top of one another and are laterally secured against displacement. Two pressure springs33engage on the upper part32, and they exert a force on the upper part32in the direction of the lower part31. A test element5can be inserted into a guide element20in the introduction direction6, between the lower part31and the upper part32, the two parts31,32are then pressed apart from each other by this test element5and the test element5fits tightly into the guide element20. The test element5can be additionally fixed in a desired position in the guide element20by the pressure of the pressure springs33.

On the side where a test element5is introduced into the test element holder19(the rear side not shown inFIG. 5), the test element holder19has a ramp- of funnel-shaped introduction opening, through which the test element5can be pushed into the guide element20. This introduction opening facilitates the introduction of a test element5which is taller than the inner height of the guide element20before introduction of the test element5.

FIG. 6shows a multi-part test element holder with oblique guide faces.

The test element holder19comprises a lower part31and an upper part32, between which a test element5can be inserted into a guide element20. The guide element20has support faces25, on which the test element5rests via bearing faces in its outer region23, and guide faces26along which the side faces34of the test element are guided. The guide faces26are in this case arranged obliquely with respect to the side faces34of the test element5, in order to avoid staining of the guide faces26by the side faces34(for example due the adhesive adhering on them).

Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modification and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein, it is contemplated that the present invention is not necessarily limed to these one aspects of the invention.