Patent Description:
Two classes of analysis systems are known in the field of medical analysis: wet analysis systems, and dry-chemical analysis systems. Wet analysis systems, which essentially operate using "wet reagents" (liquid reagents), perform an analysis via a number of required step such as, for example, providing a sample and a reagent into a reagent vessel, mixing the sample and reagent together in the reagent vessel, and measuring and analyzing the mixture for a measurement variable characteristic to provide a desired analytical result (analysis result). Such steps are often performed using technically complex, large, line-operated analysis instruments, which allow manifold movements of participating elements. This class of analysis system is typically used in large medical-analytic laboratories.

On the other hand, dry-chemical analysis systems operate using "dry reagents" which are typically integrated in a test element and implemented as a "test strip", for example. When these dry-chemical analysis systems are used, the liquid sample dissolves the reagents in the test element, and the reaction of sample and dissolved reagent results in a change of a measurement variable, which can be measured on the test element itself. Above all, optically analyzable (in particular colorimetric) analysis systems are typical in this class, in which the measurement variable is a color change or other optically measurable variable. Electrochemical systems are also typical in this class, in which an electrical measurement variable characteristic for the analysis, in particular an electrical current upon application of a defined voltage, can be measured in a measuring zone of the test element using electrodes provided in the measuring zone.

The analysis instruments of the dry-chemical analysis systems are usually compact, and some of them are portable and battery-operated. The systems are used for decentralized analysis (also called point-of-care testing), for example, at resident physicians, on the wards of the hospitals, and in so-called "home monitoring" during the monitoring of medical-analytic parameters by the patient himself (in particular blood glucose analysis by diabetics or coagulation status by warfarin patients).

In wet analysis systems, the high-performance analysis instruments allow the performance of more complex multistep reaction sequences ("test protocols"). For example, immunochemical analyses often require a multistep reaction sequence, in which a "bound/free separation" (hereafter "b/f separation"), i.e., a separation of a bound phase and a free phase, is necessary. According to one test protocol, for example, the sample can first be brought in contact with a specific binding reagent for the analyte which is immobilized onto a surface. This can be achieved for example by mixing the sample with beads comprising surfaces with such immobilized reagents or transporting the sample over surfaces or through porous matrices wherein the surfaces or the porous matrices comprise coatings of the immobilized reagents. A marking reagent can subsequently be brought in contact with this surface in a similar manner to mark the bound analyte and allow its detection. To achieve a more precise analysis, a subsequent washing step is often performed, in which unbound marking reagent is at least partially removed. Numerous test protocols are known for determining manifold analytes, which differ in manifold ways, but which share the feature that they require complex handling having multiple reaction steps, in particular also a b/f separation possibly being necessary.

Test strips and similar analysis elements normally do not allow controlled multistep reaction sequences. Test elements similar to test strips are known, which allow further functions, such as the separation of red blood cells from whole blood, in addition to supplying reagents in dried form. However, they normally do not allow precise control of the time sequence of individual reaction steps. Wet-chemical laboratory systems offer these capabilities, but are too large, too costly, and too complex to handle for many applications.

To close these gaps, analysis systems have been suggested which operate using test elements which are implemented in such a manner that at least one externally controlled (i.e., using an element outside the test element itself) liquid transport step occurs therein ("controllable test elements"). The external control can be based on the application of pressure differences (overpressure or low-pressure) or on the change of force actions (e.g., change of the action direction of gravity by attitude change of the test element or by acceleration forces). The external control can be performed by centrifugal forces, which act on a rotating test element as a function of the velocity of the rotation.

Analysis systems having controllable test elements are known and typically have a housing, which comprises a dimensionally-stable plastic material, and a sample analysis channel enclosed by the housing, which often comprises a sequence of multiple channel sections and chambers expanded in comparison to the channel sections lying between them. The structure of the sample analysis channel having its channel sections and chambers is defined by profiling of the plastic parts. This profiling is able to be generated by injection molding techniques or hot stamping. Microstructures, which are generated by lithography methods, increasingly being used more recently, however.

Analysis systems having controllable test elements allow the miniaturization of tests which have only been able to be performed using large laboratory systems. In addition, they allow the parallelization of procedures by repeated application of identical structures for the parallel processing of similar analyses from one sample and/or identical analyses from different samples. It is a further advantage that the test elements can typically be produced using established production methods and that they can also be measured and analyzed using known analysis methods. Known methods and products can also be employed in the chemical and biochemical components of such test elements.

In spite of these advantages, there is a further need for improvement. In particular, analysis systems which operate using controllable test elements are still too large. The most compact dimensions possible are of great practical significance for many intended applications.

United States patent application <CIT> describes a test element and method for detecting an analyte with the aid thereof is provided. The test element is essentially disk-shaped and flat, and can be rotated about a preferably central axis which is perpendicular to the plane of the disk-shaped test element. The test element has a sample application opening for applying a liquid sample, a capillary-active zone, in particular a porous, absorbent matrix, having a first end that is remote from the axis and a second end that is near to the axis, and a sample channel which extends from an area near to the axis to the first end of the capillary-active zone that is remote from the axis.

United States patent <CIT> discloses a test element, analytical system and method for optical analysis of fluid samples is provided. The test element has a substrate and a microfluidic channel structure, which is enclosed by the substrate and a cover layer. The channel structure has a measuring chamber with an inlet opening. The test element has a first level, which faces the cover layer, and a second level, which interconnects with the first level such that the first level is positioned between the cover layer and the second level. A part of the measuring chamber extending through the first level forms a measuring zone connecting with a part of the measuring chamber that extends partially into the second level, forming a mixing zone. Optical analysis of fluid samples is carried out by light guided through the first level parallel to the cover layer, such that the light traverses the measuring zone along an optical axis.

United States patent <CIT> discloses a microfluidic element for analyzing a bodily fluid sample for an analyte contained therein is provided, the element having a substrate, a channel structure that is enclosed by the substrate, and a cover layer, and is rotatable around a rotational axis. The channel structure of the microfluidic element includes a feed channel having a feed opening, a ventilation channel having a ventilation opening, and at least two reagent chambers. The reagent chambers are connected to one another via two connection channels in such a manner that a fluid exchange is possible between the reagent chambers, one of the reagent chambers having an inlet opening, which has a fluid connection to the feed channel, so that a liquid sample can flow into the rotational-axis-distal reagent chamber. At least one of the reagent chambers contains a reagent, which reacts with the liquid sample.

The invention provides for a method, a cartridge for an automatic analyzer, and a medical system in the independent claims. Embodiments are given in the dependent claims.

A cartridge as used here encompasses also any test element for processing a biological sample into a processed biological sample. The cartridge may include structures or components which enable a measurement to be performed on the biological sample. A typical cartridge is a test element as is defined and explained in <CIT> and <CIT>. A cartridge as used herein may also be referred to as a Centrifugal microfluidic disc, also known as "lab-on-a-disc", lab-disk or a microfluidic CD.

A biological sample as used herein encompasses as chemical product derived, copied, replicated, or reproduced from a sample taken from an organism. A blood sample is an example of a biological sample that is either whole blood or a blood product. The blood plasma may be considered to be a processed biological sample.

It is understood that references to biological samples and products below and in the claims may be modified such that they refer to blood samples and/or blood products.

In one aspect, the invention provides for a method of performing an optical measurement of an analyte in a processed biological sample using a cartridge. The cartridge is operable for being spun around a rotational axis. The cartridge comprises a support structure comprising a front face. The cartridge further comprises a fluidic structure for processing a biological sample into the processed biological sample. The fluidic structure comprises a sample inlet for receiving the biological sample.

The cartridge further comprises a measurement structure recessed from the front face. This may be alternately worded as the measurement structure is located below the front face. The measurement structure comprises a chromatographic membrane.

The chromatographic membrane may be referred to as a capillary-active zone. In one embodiment, the capillary-active zone comprises a porous, absorbent matrix. In one embodiment of the test element according to the invention, the second end of the capillary-active zone near to the axis adjoins a further absorbent material or an absorbent structure such that it can take up liquid from the capillary-active zone. The capillary-active zone and the further absorbent material typically slightly overlap for this purpose. The further material or the further absorbent structure serve on the one hand, to assist the suction action of the capillary-active zone and in particular of the porous, absorbent matrix and, on the other hand, serve as a holding zone for liquid which has already passed through the capillary-active zone. In this connection the further material can consist of the same materials or different materials than the matrix. For example, the matrix can be a membrane and the further absorbent material can be a fleece or a paper. Other combinations are of course equally possible.

The measurement structure further comprises a measurement structure inlet connected to the fluidic structure to receive the processed biological sample. The measurement structure further comprises an absorbent structure. The absorbent structure is nearer to the rotational axis than the capillary-active zone. In some examples, the absorbent structure may support the complete transport of the processed biological sample across or through the capillary-active zone and may also serve as or be a waste-fleece by binding the processed fluids and/or additional fluids like washing buffers, thus avoiding their leakage and thereby contamination of the instrument or user.

The chromatographic membrane extends from the measurement structure inlet to the absorbent structure. The absorbent structure may be absorbent and therefore fluids or liquids that are placed in the measurement structure inlet may wick to the absorbent structure. The chromatographic membrane comprises a detection zone. The measurement structure comprises an inlet air baffle connected to the front face. An air baffle as used herein is a mechanical structure that is used to restrict the flow of air or other gas. The inlet air baffle serves as a vent to the atmosphere surrounding the cartridge to the chromatographic membrane.

The method comprises placing the biological sample into the sample inlet. The method further comprises controlling the rotational rate of the cartridge to process the biological sample into the processed biological sample using the fluidic structure. In different examples this may take different forms. For example the biological sample may be diluted, or it may be mixed with other chemicals which change the biological sample chemically or the biological sample may be mixed with antibodies that react with the analyte and provide markers which can then be layered on the chromatographic membrane. The method further comprises controlling the rotational rate of the cartridge to allow the processed biological sample to flow from the measurement structure inlet to the absorbent structure via the chromatographic membrane.

The absorbent structure serves on the one hand, to assist the suction action of the chromatographic membrane or capillary-active zone and in particular of the porous, absorbent matrix and, on the other hand, serve as a holding zone for liquid which has already passed through the capillary-active zone. In this connection the further material can consist of the same materials or different materials than the matrix. For example, the matrix can be a membrane and the further absorbent material can be a fleece or a paper. Other combinations are of course equally possible.

The air inlet baffle reduces the evaporation of the processed biological sample during rotation of the cartridge. The method further comprises performing the optical measurement of the detection zone with an optical instrument. The optical instrument for example may be a spectrographic instrument.

This embodiment may be beneficial because the air inlet baffle may reduce the access of air or the atmosphere surrounding the cartridge when it is spun. Reducing the evaporation of the processed biological sample may be beneficial in that it may provide for more accurate measurements. In other cases, because the evaporation is reduced, the biological sample may function if a smaller volume is used. In other examples the inlet air baffle may provide the benefit that less additional fluid needs to be mixed with the biological sample to turn it into the processed biological sample.

The fluidic structure may contain a reagent zone which contains a conjugate of an analyte binding partner (typically an antibody or an immunologically active antibody fragment capable of analyte binding if the analyte is an antigen or hapten, or an antigen or hapten if the analyte is an antibody) and a label which can be detected directly or indirectly by visual, optical or electrochemical means, wherein the conjugate can be dissolved by the liquid sample. Suitable labels are, for example, enzymes, fluorescent labels, chemiluminescent labels, electrochemically active groups or so-called direct labels such as metal or carbon labels or colored lattices. This zone may also referred to as the conjugate zone.

The conjugate zone can serve also as a sample application zone or a separate sample application zone can be located on the test element. The conjugate zone can, in addition to the conjugate of analyte binding partner and label described above, also contain an additional conjugate of a second analyte binding partner (which is in turn typically an antibody or an immunologically active antibody fragment capable of analyte binding) and a tagging substance which is itself a partner in a binding pair. The tagging substance can for example be biotin or digoxigenin and can be used to immobilize a sandwich complex consisting of labelled conjugate, analyte and tagged conjugate in the detection and/or control zone.

The chromatographic membrane may additionally comprise a detection zone which contains a permanently immobilized binding partner (i.e., one that cannot be detached by the liquid sample) for the analyte or for complexes containing the analyte. The immobilized binding partner is in turn typically an antibody or an immunologically active antibody fragment capable of analyte binding or an antigen or (poly)hapten. If one of the above-mentioned tagged conjugates is used which for example comprises biotin or digoxigenin together with an analyte binding partner, the immobilized binding partner can also be streptavidin or polystreptavidin and an anti-digoxigenin antibody.

Finally, there may also be a control zone in or on the chromatographic membrane which contains a permanently immobilized binding partner for the conjugate of analyte binding partner and label for example in the form of an immobilized polyhapten which acts as an analyte analogue and is able to bind the analyte binding partner from the labelled conjugate. The control zone may additionally contain one or more permanently immobilized binding partner(s) for the analyte or for complexes containing the analyte. The latter binding partners can be selected from the same compounds which were described above in connection with the immobilized binding partners of the detection zone. These immobilized binding partners in the detection zone and in the control zone are typically identical. They may, however, also be different for example in that a binding partner for a biotin-tagged conjugate (hence, e.g., polystreptavidin) is immobilized in the detection zone and an anti-analyte antibody is immobilized in the control zone in addition to the polyhapten. In the latter case the anti-analyte antibody that is additionally immobilized in the control zone should be directed against (another) independent epitope and thus one that is not recognized by the conjugate antibodies (biotin-tagged conjugate and labelled conjugate).

In another embodiment, the absorbent structure is a waste fleece.

In another embodiment, the chromatographic membrane can contain one or more zones containing immobilized reagents.

Specific binding reagents for example specific binding partners such as antigens, antibodies, (poly) haptens, streptavidin, polystreptavidin, ligands, receptors, nucleic acid strands (capture probes) are typically immobilized in the capillary-active zone and in particular in the porous, absorbent matrix. They are used to specifically capture the analyte or species derived from the analyte or related to the analyte from the sample flowing through the capillary-active zone. These binding partners can be present immobilized in or on the material of the capillary-active zone in the form of lines, points, patterns or they can be indirectly bound to the capillary-active zone e.g., by means of so-called beads. Thus, for example, in the case of immunoassays one antibody against the analyte can be present immobilized on the surface of the capillary-active zone or in the porous, absorbent matrix which then captures the analyte (in this case an antigen or hapten) from the sample and also immobilizes it in the capillary-active zone such as, e.g., the absorbent matrix. In this case the analyte can be made detectable for example by means of a label that can be detected visually, optically or fluorescence-optically by further reactions, for example by additionally contacting it with a labelled bindable partner.

In another embodiment, the fluidic structure contains a first specific binding partner of the analyte with a detectable label and a second specific binding partner with a capture label. These both form a binding complex with the analyte. This may consist of a first specific binding partner, a second specific binding partner and an analyte. This may additionally provide for a measurement structure within the immobilized binding partner specific to the capture label of the second specific binding partner.

In another embodiment, the detection is fluorescence-based.

In another embodiment, the label is particle-based fluorescent label.

In another embodiment, the chromatographic membrane contains an optical calibration zone. The optical calibration zone may for example be a region on the measurement structure which contains a defined amount of the immobilized label and provides a means for checking if the optics of the instrument is functioning properly and if not, to calibrate it adequately. In other embodiments, the optical calibration zone is located at different locations on the test element.

In another embodiment, the measurement structure contains a reagent and flow control zone. This may provide for a means of checking if the cartridge is functioning properly in terms of reagents and immunochromatography. There may be for example two different control zones, a reagent/flow-control and an optical calibration zone as instrument control zone for correcting the intensity of the radiation or excitation source when an optical measurement is made.

In another embodiment, the cartridge is disk-shaped or at least partially disk-shaped.

In another embodiment, the cartridge may have an outer edge which fits within a circle drawn around the rotational axis.

In another embodiment, the cartridge has an outer edge. The outer edge may have a portion or portions that are circularly symmetric around the rotational axis.

In another embodiment, the method further comprises placing the buffer solution at the measurement structure inlet after controlling the rotational rate of the cartridge to allow the processed biological sample to flow from the measurement structure inlet to the absorbent structure via the chromatographic membrane. The method further comprises cleaning or washing the chromatographic membrane by controlling the rotational rate of the cartridge to allow the buffer solution to flow from the measurement structure inlet to the absorbent structure via the chromatographic membrane before performing the optical measurement. The use of the buffer solution may be beneficial because it may provide for a more accurate and reproducible measurement of the analyte. The use of the cartridge with the inlet air baffle may further increase this benefit as it may reduce the evaporation of the buffer solution in addition to reducing the evaporation of the biological sample. This may allow less buffer solution to be used and may also provide for a more controlled transport of the buffer solution across the chromatographic membrane to the absorbent structure.

In another aspect, the invention provides for a cartridge for an automatic analyzer. The cartridge is operable for being spun about a rotational axis. The cartridge comprises a support structure. The support structure comprises a front face. The cartridge further comprises a fluidic structure for processing a biological sample into a processed biological sample. The fluidic structure comprises a sample inlet for receiving the biological sample. The cartridge further comprises a measurement structure recessed from the front face. The measurement structure comprises a chromatographic membrane. The measurement structure comprises a measurement structure inlet connected to the fluidic structure to receive the processed biological sample. The measurement structure comprises an absorbent structure. The chromatographic membrane extends from the measurement structure inlet to the absorbent structure. The measurement structure comprises an air inlet baffle connected to the front face.

In embodiments of the invention, the entire detection zone is open to the front face via the first air baffle structure along a directed path. In other words the entire measurement zone is able to be exposed to direct measurement from an optical instrument. There is no optically transparent region which shields the measurement zone of the chromatographic membrane in this embodiment. The directed path is parallel to the rotational axis. This embodiment may provide for a better measurement of the measurement zone using the optical instrument.

In another embodiment, the measurement structure comprises at least one air pocket adjacent to the chromatographic membrane. The at least one air pocket is covered by the front face parallel to the rotational axis. This means that if one starts in the air pocket and then traces a path in a direction parallel to the rotational axis, the front face shields or covers the air pocket. The air pocket for instance may be a region adjacent to the chromatographic membrane which is covered by the front face. The use of the air pocket may be beneficial because it may help to trap air around the chromatographic membrane and reduce the evaporation.

In another embodiment, the measurement zone is within certain spots or locations of the chromatographic membrane. The inlet air baffle and the outlet air baffle may be holes or multiple holes which are located in the front face in a direction parallel to the rotational axis.

In another embodiment along a circumferential path across the detection zone the inlet air baffle has a first air baffle edge and a second air baffle edge where the inlet air baffle meets the front face. The first air baffle edge and the second air baffle edge for instance may be a raised area of the front face which helps to prevent air from reaching the chromatographic membrane as the cartridge is rotated about the rotational axis.

In another embodiment along the rotational axis the first air baffle edge is further from the chromatographic membrane than the second air baffle edge. This may be beneficial because the first air baffle edge may be used to disrupt the flow of air to the chromatographic membrane and placing the second air baffle edge closer to the chromatographic membrane may reduce the amount of turbulence. This may help to reduce evaporation from the chromatographic membrane.

In another embodiment, the front face has an average distance from the chromatographic membrane along the rotational axis. The first air baffle edge and the second air baffle edge are further from the chromatographic membrane than the front face along the rotational axis. Placing the first air baffle edge and the second air baffle edge further away from the chromatographic membrane may reduce the amount of evaporation from the chromatographic membrane.

The first air baffle edge and the second air baffle edge may also be described as ridges or raised areas adjacent to the chromatographic membrane. The average distance of the front face may be taken about a circumference or rotational path about the rotational axis.

In another aspect, the invention provides for a medical system. The medical system comprises a cartridge according to any one of the preceding embodiments. The medical system further comprises an automatic analyzer configured for receiving the at least one cartridge. The automatic analyzer comprises a cartridge spinner, an optical instrument, and a controller configured to control the automatic analyzer.

The controller is configured to control the rotational rate of the cartridge to process the biological sample into the processed biological sample using the fluidic structure. The processed biological sample is mixed with the buffer solution. In some examples the automatic analyzer may also place the biological sample into the sample inlet. However, in other examples this may be done by an operator before placing the at least one cartridge into the automatic analyzer. The controller is further configured to control the rotational rate of the cartridge to allow the processed biological sample to flow across the chromatographic membrane from the measurement structure. The inlet air baffle reduces the evaporation of the processed biological sample. The controller is further configured to control the optical instrument to perform the optical measurement of the detection zone with the optical instrument.

In another embodiment the medical system comprises the at least one cartridge.

It is understood that one or more of the aforementioned embodiments and/or examples of the invention may be combined as long as the combined embodiments are not mutually exclusive.

In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:.

<FIG> shows a top view of an unclaimed cartridge <NUM> provided as an example. The cartridge comprises a support structure <NUM>. The front face <NUM> is facing towards the viewer in this view. The cartridge <NUM> is circular and has an edge <NUM> that is rotationally symmetric about a rotational axis <NUM>. In this example the rotational axis <NUM> is viewed directly on in this front view. In other examples the edge <NUM> may not be rotationally symmetric about the entire edge <NUM>. There may for example be flat regions which are useful for holding or gripping the cartridge <NUM>. The cartridge <NUM> comprises a fluidic structure <NUM> which is within the support structure <NUM>. The fluidic structure <NUM> may comprise a sample inlet <NUM>. The cartridge <NUM> also comprises a measurement structure <NUM>. The measurement structure <NUM> comprises a measurement structure inlet <NUM> which has a connection <NUM> to the fluidic structure <NUM>. The sample inlet <NUM> may be for receiving a biological sample. The fluidic structure <NUM> is intended to be arbitrary and represent a fluidic structure which can be used to process the biological sample into a processed biological sample which can then be transported via the connection <NUM> to the measurement structure inlet <NUM>.

The measurement structure <NUM> further comprises a chromatographic membrane <NUM> which is recessed from the front face <NUM>. The measurement structure <NUM> also comprises a absorbent structure <NUM> which is absorbent. Fluid placed in the measurement structure inlet <NUM> will wick through or across the chromatographic membrane <NUM> towards the absorbent structure <NUM>. There may be antibodies or other reactive chemicals placed on the chromatographic membrane <NUM> within a detection zone <NUM>. Portions of the analyte to be measured may then stick or stay at the detection zone <NUM>. Other antibodies added with the fluidic structure <NUM> may for instance contain fluorescent markers which may be detected by an optical instrument. The front face <NUM> may have an optically transparent area <NUM> above the detection zone <NUM> such that optical measurements can be performed. In this example there is a static cover <NUM>. The optically transparent <NUM> is a region of the static cover <NUM>.

As fluid is transported across the chromatographic membrane <NUM> there may be condensation which builds up on the underside of the optically transparent area <NUM> that is adjacent to the chromatographic membrane <NUM>. This may cause condensation which may cause errors or prevent the optical measurement of the detection zone <NUM>. To prevent this there is an inlet air baffle <NUM> and an outlet air baffle <NUM>. This enables a small or reduced amount of air to pass beneath the optically transparent area <NUM> to help keep it free from condensation. Above the chromatographic membrane <NUM> is a portion of the front face <NUM>. Having a structure such as plastic above the chromatographic membrane <NUM> helps to reduce evaporation. This may increase the reproducibility and/or sensitivity of the measurement of the analyte by optical means.

The system illustrated in <FIG> is intended to be representative. There may also be a system for dispensing a buffer solution to the measurement structure inlet <NUM>. This is not shown in the Fig. but it may be beneficial that after the processed biological sample has been transported across the detection zone <NUM> that a buffer is used to wash and help clean the chromatographic membrane <NUM>. This may increase the sensitivity and/or reproducibility of the measurement of the analyte.

The dashed line <NUM> shows a cross-section which is used to illustrate a cross-sectional view in <FIG>.

<FIG> shows a cross-sectional view <NUM> along the dashed line <NUM> of <FIG>. The cross-sectional view <NUM> shows the support structure <NUM>. The support structure <NUM> for instance may be molded plastic which contains the fluidic structure that is molded. In this figure an air volume <NUM> between the static cover <NUM> and the chromatographic membrane <NUM> is shown.

<FIG> shows an alternate cross-sectional view <NUM> of an unclaimed cartridge provided as an example. The example shown in <FIG> is similar to that in <FIG> except the surfaces of the inlet air baffle <NUM> and the outlet air baffle <NUM> have been more smoothed to reduce turbulence. The smooth surfaces may reduce the chances of turbulence forming within the air volume <NUM>. This may further reduce the amount of evaporation from the chromatographic membrane <NUM>. It can be seen that the inlet air baffle <NUM> has a first continuously smooth surface <NUM>. The outlet air baffle <NUM> has a second continuously smooth surface <NUM>. The optically transparent area <NUM> also is shown as having been smoothed.

<FIG> shows a modification of the cartridge <NUM> as shown in <FIG> that is unclaimed and is provided as an example. The structures shown in <FIG> are nearly identical to those shown in <FIG> except the inlet air baffle <NUM> and the outlet air baffle <NUM> are constructed differently. The dashed line <NUM>' shows a further cross-sectional view which is illustrated in <FIG>.

<FIG> shows a further unclaimed example. In the cross-sectional view <NUM> of <FIG> it can be seen that the structure is nearly identical with what is present in <FIG>. In this example the optically transparent area <NUM> has been thicker to reduce airflow through the air volume <NUM>. Also the inlet air baffle <NUM> and the outlet air baffle <NUM> have been enlarged by placing a chamfer <NUM> in the support structure <NUM>. This may help to further reduce turbulence and reduce evaporation at the chromatographic membrane <NUM>.

<FIG> shows a further variant of the cartridge <NUM> that is unclaimed and is provided as an example. The example shown in <FIG> is very similar to the example shown in <FIG> except in this case the inlet air baffle <NUM>' has become smaller than is shown in <FIG>. Likewise the outlet air baffle <NUM>' is also smaller than the outlet air baffle <NUM> in <FIG>. On this Fig. can be seen a line <NUM> which is drawn from the rotational axis <NUM> through the detection zone <NUM>. When measured along the line <NUM>, it can be seen that the outlet air baffle <NUM>' and the inlet air baffle <NUM>' have been made smaller along the direction <NUM> than was in previous embodiments. The inlet <NUM>' and the outlet <NUM>' are now smaller in dimension than the detection zone <NUM>. One of the two is also placed closer to the rotational axis <NUM> than the other. Reducing the size of the inlet <NUM>' and outlet <NUM>' may have the effect of reducing the amount of evaporation from the chromatographic membrane <NUM>. Also their placement can be used to force air going from the inlet <NUM>' to the outlet <NUM>' to follow a particular path across the optically transparent area <NUM>. In this particular example the outlet air baffle <NUM>' is shown as being closer to the rotational axis <NUM> than the inlet air baffle <NUM>'. These two may be reversed.

<FIG> shows a further cross-sectional view <NUM> which is alternate to those shown in <FIG>, and <FIG>. <FIG> also shows an unclaimed example. In the example shown in <FIG> there is a static cover <NUM> which is sloped. The cross-sectional view has the appearance of an air foil. The static cover <NUM> in this shape has the effect of either directing air away from the air volume <NUM> or directing air into it. This can be used to preferentially reduce evaporation from the chromatographic membrane <NUM> or to force a small amount of air into the air volume <NUM> to remove or prevent condensation on the underside <NUM>. The static cover <NUM> is part of the front face <NUM> and is fixed in position over the chromatographic membrane <NUM>.

The thickness of the static cover <NUM> varies when measured along the direction <NUM>. It is possible that this variation in thickness acts as a lens for light coming from the chromatographic membrane <NUM>. In some cases the optical measurement system may have an optical component or lens which compensates for this effect.

In <FIG> it can be seen that the static cover <NUM> has a first edge <NUM> and a second edge <NUM>. The dashed line <NUM> indicates a direction parallel to the rotational axis. Measured parallel to the rotational axis <NUM> the first edge <NUM> is a first distance <NUM> from the chromatographic membrane <NUM>. The second edge <NUM> is a second distance <NUM> from the chromatographic membrane <NUM>. The distance <NUM> is smaller than the distance <NUM>. It can also be seen in this <FIG> that the front face <NUM> on either side of the static cover <NUM> has portions which are different distances from the chromatographic membrane <NUM>. Adjacent to the first edge <NUM> the front face <NUM> is a third distance <NUM> from the chromatographic membrane. The area of the front face <NUM> adjacent to the second edge <NUM> is a fourth distance <NUM> from the chromatographic membrane <NUM>. The distances <NUM>, <NUM>, <NUM> and <NUM> are measured parallel to the rotational axis <NUM>. The first edge <NUM> at least partially forms the inlet air baffle <NUM>. The second edge <NUM> forms part of the outlet air baffle <NUM>. Placing the first edge <NUM> above the front face <NUM> causes the inlet air baffle <NUM> to be like a scoop. When the second edge <NUM> is moved towards the first edge <NUM> rotationally this causes a scoop-like effect which forces air into the air volume <NUM>. When the cartridge is rotated in the opposite direction such that the first edge <NUM> is moved in the direction of the second edge <NUM> then the air passes over the outer surface of the static cover <NUM> more easily. This may reduce airflow through the air volume <NUM>. And have the effect of reducing evaporation of a fluid from the chromatographic membrane <NUM>.

<FIG> shows a further alternate cross-sectional view <NUM>. In this example the static cover <NUM> is absent. In this example only the inlet air baffle <NUM> is present. The dashed line <NUM> again marks a direction parallel to the rotational axis. It can be seen that if a line <NUM> is taken parallel to the rotational axis <NUM> that there is a directed path <NUM> from the detection zone <NUM> which is not obstructed by the front face <NUM>. To the side of the chromatographic membrane is an air pocket <NUM>. There is an air pocket <NUM> on either side of the membrane <NUM>. A path <NUM> parallel <NUM> to the rotational axis from the air pocket <NUM> reaches the front face <NUM>. The effect of the air pockets <NUM> is to trap air in the space above the chromatographic membrane <NUM>. This reduces the evaporation of fluid from the chromatographic membrane <NUM>. The open space above the chromatographic membrane <NUM> can also be selectively placed above the detection zone <NUM>. This would also eliminate the potential difficulty caused by condensation on the underside of the static cover <NUM>.

<FIG> shows a further cross-sectional view <NUM>. Again, like <FIG> there is a directed path <NUM> in a direction <NUM> parallel to the rotational axis that exposes the detection zone <NUM>. In this embodiment <NUM> there are no air pockets. Instead there is a first air baffle which has a first air baffle edge <NUM> and a second air baffle edge <NUM>. In the direction <NUM> parallel to the rotational axis the first air baffle edge <NUM> is a distance <NUM> from the chromatographic membrane <NUM>. The front face is a distance <NUM> from the chromatographic membrane and the second air baffle edge <NUM> is a distance <NUM> from the chromatographic membrane <NUM>. As the cartridge <NUM> is rotated the first air baffle edge <NUM> disrupts airflow to the chromatographic membrane <NUM> reducing the evaporation of fluid. In this example the second air baffle edge <NUM> is shown such that the distance <NUM> and <NUM> are equal. In other embodiments the distance <NUM> could be increased such that it is equal to or less than the distance <NUM>.

<FIG> shows an alternative cross-sectional view <NUM>. The cross-sectional view <NUM> is similar to that of <FIG> except the distance <NUM> has been increased such that it is equal to the distance <NUM>.

<FIG> shows an example of a medical system <NUM>. The medical system <NUM> is adapted for receiving a cartridge <NUM>. There is a cartridge spinner <NUM> which is operable for rotating the cartridge <NUM> about the rotational axis. The cartridge spinner <NUM> has a motor <NUM> attached to a gripper <NUM> which attaches to a portion of the cartridge <NUM>. The cartridge <NUM> is shown further as having a measurement structure <NUM>. The cartridge <NUM> can be rotated such that the measurement structure <NUM> goes in front of an optical measurement system <NUM> which can perform for example an optical measurement of the quantity of the analyte. An actuator <NUM> is optionally shown in this Fig. It can be used to open fluid reservoirs in the cartridge <NUM> or manipulate a dispenser to provide buffer solution to the cartridge. There may also be additional actuators or mechanisms for actuating mechanical valves or valve elements on the cartridge if they are present.

The actuator <NUM>, the cartridge spinner <NUM>, and the measurement system <NUM> are shown as all being connected to a hardware interface <NUM> of a controller <NUM>. The controller <NUM> contains a processor <NUM> in communication with the hardware interface <NUM>, electronic storage <NUM>, electronic memory <NUM>, and a network interface <NUM>. The electronic memory <NUM> has machine executable instructions which enable the processor <NUM> to control the operation and function of the medical system <NUM>. The electronic storage <NUM> is shown as containing a measurement <NUM> that was acquired when instructions <NUM> were executed by the processor <NUM>. The network interface <NUM> enables the processor <NUM> to send the measurement <NUM> via network connection <NUM> to a laboratory information system <NUM>.

Claim 1:
A method of performing an optical measurement (<NUM>) of an analyte in a processed biological sample using a cartridge (<NUM>), wherein the cartridge is operable for being spun around a rotational axis (<NUM>), wherein the cartridge comprises:
- a support structure (<NUM>) comprising a front face (<NUM>);
- a fluidic structure (<NUM>) for processing a biological sample into the processed biological sample, wherein the fluidic structure comprises a sample inlet (<NUM>) for receiving the biological sample; and
- a measurement structure (<NUM>) recessed from the front face, wherein the measurement structure comprises a chromatographic membrane (<NUM>), wherein the measurement structure comprises a measurement structure inlet (<NUM>) connected to the fluidic structure to receive the processed biological sample, wherein the measurement structure comprises an absorbent structure (<NUM>), wherein the chromatographic membrane (<NUM>) extends from the measurement structure inlet to the absorbent structure (<NUM>), wherein the chromatographic membrane (<NUM>) comprises a detection zone (<NUM>), wherein the measurement structure comprises an inlet air baffle (<NUM>, <NUM>') connected to the front face, wherein the entire detection zone is open (<NUM>, <NUM>, <NUM>) to the front face via the first air baffle structure along a directed path (<NUM>), and wherein the directed path is parallel (<NUM>) to the rotational axis;
wherein the method comprises:
- placing the biological sample into the sample inlet;
- controlling (<NUM>) the rotational rate of the cartridge to process the biological sample into the processed biological sample using the fluidic structure;
- controlling (<NUM>) the rotational rate of the cartridge to allow the processed biological sample to flow from the measurement structure inlet to the absorbent structure via the chromatographic membrane, wherein the inlet air baffle reduces the evaporation of the processed biological sample during rotation of the cartridge; and
- performing (<NUM>) the optical measurement of the detection zone with an optical instrument.