EP0847804A2 - System for transporting and storing samples - Google Patents

Abstract

A system for storing and transporting sample materials on absorbent material (AM) contains no test reagents and comprises AM for absorption of a liquid sample enclosed in a closable container together with a moisture absorbing medium (MAM).

Description

The invention relates to a system for storing and transporting sample material absorbent material.

Glycation of hemoglobin and serum proteins is increased in patients with diabetes mellitus. The increase depends on the glucose concentration and the incubation time of the protein with glucose. In these cases, the glycation of serum proteins, including hemoglobin, is not carried out enzymatically, but uncatalyzed by chemical reaction of the glucose with amino groups of the proteins. The expert assumes that the concentration of a certain protein-glucose adduct reflects both the glucose concentration over a certain time and the conversion rate of the protein. Glycated hemoglobin is considered an indicator of the mean blood glucose concentration during the last two to three months before blood collection and examination. Glycated serum protein reflects the blood glucose concentration over a shorter period of time. The determination of glycated protein such as glycated hemoglobin (HbA _1c ) or glycated serum protein is therefore of great importance for the long-term glycemic control of diabetes patients.

To test blood for glycated protein content, the sample often has to be transported to a distant laboratory. The content of glycated protein in the sample should not change as much as possible during this transport time and any subsequent waiting time. Clinical Chemistry 29 , 1080-1082 (1983) reports the examination of blood samples for glycated hemoglobin that have been stored for a long time. It follows from this that whole blood can be stored at room temperature for up to 21 days without the HbA _1c content changing significantly.

However, the transport of liquid blood samples is complex and involves risks, such as breakage of the transport container. In addition, venipuncture is often necessary for the collection of whole blood, although the sample itself would also be sufficient for the small amounts of sample that are obtained when the capillary blood is taken from the fingertip. For this reason, methods have been developed for the transport and investigation of smaller sample quantities in which capillary blood is placed on filter paper and allowed to dry there. The filter paper is then transported to the location of the examination. There a disk with sample is punched out of the filter paper, eluted and the eluate examined. The report in Clinical Chemistry 28 , 386-387 (1982) relates to such a method. This report states that when the blood sample is stored on filter paper, the glycated protein content changes significantly compared to the original sample. After storing whole blood on filter paper, significantly increased measured values for glycated protein are found.

Clinical Chemistry 32 , 869-871 (1986) describes the impregnation of filter paper with glucose oxidase to prevent the increase in the glycated hemoglobin content caused by blood being stored on filter paper. However, impregnation with glucose oxidase cannot completely prevent the increase in glycated protein. The wrong increase in value can only be reduced by this measure. Another disadvantage of impregnation with glucose oxidase is its own instability during storage under normal storage conditions.

Similar results from an article in Diabetes Care 10 , 352-355 (1987). There it is reported that the treatment of filter paper with glucose oxidase or also with ethanol cannot satisfactorily prevent a false increase in the value of glycated hemoglobin when blood is stored on filter paper.

In addition to the poor stability of the sample, another disadvantage is that of the prior art described methods for transporting and storing sample materials therein see that the liquid sample is fully rocked before final packaging got to. For this purpose, the filter paper must typically be air-dried for 10 to 60 minutes. Incompletely dried samples can lead to non-reproducible test results or contaminate the shipping packaging, for example.

The object of the present invention was therefore to overcome the disadvantages of the prior art Eliminate technology. In particular, the level of glycated protein in a sample should contribute Storage can be stabilized on an absorbent material. Glycated after storage Proteins on an absorbent material should find a value for the glycated protein as it existed after sampling and before storage. Furthermore, the handling the carrier containing sample material can be simplified and made safer.

This object is achieved by the subject-matter characterized in more detail in the patent claims solved.

The invention relates to a system for storing and transporting sample material. The system consists of an absorbent material for absorbing liquid samples, a closable one Container in which the material can be stored and transported, and one moisture absorbing medium.

It is essential for the system according to the invention that none in the system itself Test reagents are included. In particular, the absorbent material which the Absorption of the sample material is used, no test reagents.

In this context, test reagents are those reagents or substances that usually in analytical test elements, such as colorimetric test strips or electrochemical sensors and biosensors are included and the detection of one Serve target analytes. In other words, test reagents are substances that work with the target analyte enter into an interaction, the detection of which directly or indirectly, the means, if necessary, only after adding additional reagents. For example called enzymes, coenzymes, dyes, mediators, pH and redox indicators, immunological detection reagents such as antibodies or antigens, ionophores, Complexing agents and the like.

Test reagents should not include reagents or substances that are not directly detectable serve as a target analyte. Such substances are not allowed with the target analyte in the sample Enter into an interaction that allows its detection. Examples include stabilizers, which also includes enzyme substrates and coenzymes, which are mainly used for Stabilization of the analyte serve, buffer substances, spreading agents and other usual, the Substances familiar to experts.

The system according to the invention is for transporting and storing items to be analyzed Sample material, in particular liquid samples, especially body fluids such as blood, Plasma, serum, urine, saliva etc. are suitable. The invention is particularly preferred Element used to transport and store blood samples.

Papers, filter papers, Nonwovens, woven fabrics, knitted fabrics and membranes, possibly on an additional inert Carriers, as they are known to those skilled in the art, have been found to be suitable. Prefers fibrous materials are used as absorbent materials, although in principle also non-fibrous materials, such as membranes, can be used. Preferred fibrous Absorbent materials are nonwovens, woven or knitted fabrics. Nonwovens are particularly preferred. The fibrous materials can be glass, cellulose, polyester but also viscose and contain polyvinyl alcohol. Nonwoven materials containing meltable copolyester fibers in addition to glass fibers, polyester fibers, polyamide fibers, cellulose fibers or cellulose derivative fibers, as described in European patent application 0 571 941 can also can be used advantageously in the element according to the invention.

Depending on the analyte to be analyzed, it must be ensured that this is based on the task and Drying of the sample material onto the absorbent material then reproducible again can be eluted. The specialist can carry out simple elution experiments for this, to get certainty.

The absorbency can be determined according to DIN 53106. For this, samples of 200 +/- 1 mm length and 15 +/- 0.1 mm width perpendicular with its lower end 25 mm in distilled Water immersed and the distance the water travels in 10 minutes is measured in mm.

How different absorbencies are set for materials with the same components can be known to the person skilled in the art. For example, in the manufacture of nonwovens Fibers of different thickness are used. The thicker the fibers used, the lower the absorbency. Another way is to vary the density of fleeces. The absorbency is reduced by increasing the density.

When using fabrics, fabrics with finer fibers have greater absorbency as a fabric with coarser fibers. But also about different types of twisting the threads can control absorbency. You can also use the weaves Differences in absorbency can be achieved. Other variations of the Absorbency can be achieved by using different fiber blends will. The addition of hydrophobic fibers, for example, improves absorbency decreased.

As an inert carrier material for the absorbent materials that can be used according to the invention stiff materials are particularly suitable, such as plastic films, cardboard, coated paper etc.

The absorbent material is attached to the inert carrier material in such a way that the absorption of liquid is not affected by the absorbent materials. This is through use a double-sided adhesive tape or, for example, by using Hot melt adhesive possible.

In a particularly preferred embodiment of the invention, two layers of absorbent material are arranged next to one another in a touching manner on an inert carrier material such that a liquid transfer from the first to the second layer is possible when the first layer is filled with liquid. The absorbency of the matrix material of the first layer should be the same as or greater than that of the second adjacent layer. This avoids the formation of disturbing suction effects when sample material is applied to the first layer.
In the particularly preferred embodiment described above, the layers of the absorbent material must be attached to the inert carrier in such a way that the first layer can be completely separated from the second layer after application and drying of liquid sample material. This is particularly possible if the first layer is only attached relatively loosely or only at certain points.

Furthermore, in the particularly preferred embodiment described above, the two layers of the absorbent material so touching each other on the backing material be arranged so that a liquid transfer from the first layer into the second Layer is possible if the first layer is filled with liquid. This is then possible if there is at least edge contact between the two layers. But is even better a slight overlap of the two layers is provided. Those are particularly preferred Layers are then arranged so that the second layer slightly overlaps the first layer.

For the particularly preferred embodiment described above, the size of the Layers of the absorbent material are chosen so that the first layer, which later also is used as an evaluation layer with which the sample liquid can be filled completely. Excess sample liquid is then taken up by the second layer. Which Amounts of sample sufficient to determine a particular analyte depends on the type of the analyte to be determined. As a rule, however, 5-20 µl, usually 10 µl sample are sufficient out. This volume must be taken up by the first matrix layer and later again can be eluted. For safety, the second matrix layer, which functions as a Absorbent layer, can take up a larger volume. Suction volume of 10-50 µl, preferably 10-30 µl, particularly preferably 20 µl are usually sufficient for this. Conveniently the usual dimensions of the layers of absorbent material should be like this be such that the suction volume of the two layers taken together is at least 30 µl, better at least 50 µl. Such a dimensioning ensures that with both small and large drops of liquid on the first matrix layer different elements of the invention the same amount of sample is applied. The The smaller first layer usually has one to achieve a sufficient suction volume Area from 3x3 to 8x8 mm.

Due to the above-described, particularly preferred arrangement of the layers of the absorbent A homogeneous distribution of liquid sample material is achieved in the first layer. Because the first layer is completely filled with liquid sample material concentration gradients of the analyte cannot form within this layer, otherwise always to be observed in the peripheral zones of the elements of the prior art were. Concentration-related measurement differences when determining analytes are avoided.

To separate in the particularly preferred embodiment described above To ensure the first of the second layer of absorbent material are different arrangements of the layers on the carrier material conceivable. Very particularly preferred embodiments for absorbent materials attached to a carrier are shown in Figures 1 and 2 shown.

The element according to the invention according to FIG. 1 carries layers of an absorbent material 1, 2 at one end of an inert carrier material 3. The layers are double-sided by means of a adhesive tape 4 attached to the carrier material 3. The layers 1, 2 are so on the Carrier material 3 arranged that they are at the end of this carrier material 3. The first Layer of the absorbent material 1, which is provided for the sample application, lies at the end of the carrier material 3 closest. It is slightly overlapped by the second layer of the absorbent material 2, which absorbs excess liquid of the sample material when the first layer 1 is filled. At the end of the carrier material 3 below the first layer 1 there is a recess 5 in the carrier material 3. This recess 5 enables or makes it easier to grip the first layer 1, for example with a pair of tweezers, in order to Remove from the element for purposes of elution and subsequent analysis steps.

In the element according to the invention according to FIG. 2, the two layers are absorbent Material 1, 2 attached to the inert support material 3 so that two opposite Ends of the carrier material 3 are free and can be gripped with the fingers. The two layers of the absorbent material 1, 2 are on the carrier material by means of double-sided adhesive tape 4, 6 3 attached. The carrier material 3 has a predetermined breaking point 7, which is arranged that when bending, breaking or tearing, the element can be divided into two parts there, that the one the first layer of absorbent material 1 and the other the second layer absorbent material 2 carries. In the case of a plastic film as the carrier material 3, the Breakage 7 should be a notch. However, there can also be a corresponding perforation there are present, which makes it possible to bend two separate parts at this point Get parts.

In a further preferred embodiment, the absorbent material of the invention Systems auxiliaries that are suitable for spreading the liquid sample. Such Auxiliaries are known to experts and their use is familiar to the person skilled in the art. By spreading the sample will result in an even, homogeneous distribution of the sample material and caused in the absorbent material. When using filter paper, for example As an absorbent material, this measure ensures that small samples of the Filter paper containing the previously applied sample material, which is used for elution purposes cut or punched out of the filter paper, reproducible quantities Sample material included.

In a further preferred embodiment, the sample application zone is the absorbent Material marked. The marking can be made directly on or in the absorbent material attached or contained or optionally applied to the inert carrier. This enables the user to precisely place the sample at the preferred point of application facilitated. This measure also serves to ensure the reproducibility of the sample application to increase.

It is further preferred that handling instructions for and / or the users of the invention Systems are included in this. The handling instructions are particularly preferred on the absorbent material, optionally the inert carrier or the sealable Container attached. The handling instructions are very particularly preferred attached to the absorbent material.

The closable container of the system according to the invention serves for mechanical stabilization of the absorbent material containing sample material during storage and transport. The closable container preferably consists of a stiffened, flangeable Envelope, a bag that can be flanged, which may be placed in a rigid envelope can be, or a tube closable with a plug or lid. A sealable with a sealing plug or lid is particularly preferred Tubes used. The tube preferably consists of a dimensionally stable, unbreakable and material which is inert with respect to the sample, for example made of plastics, metals, Alloys, paper or cardboard, possibly with plastics, metals and / or Alloys are coated, ceramic or glass. Use has proven to be particularly preferred of polyethylene, polypropylene or aluminum.

In addition to mechanical stabilization, the lockable container in combination with a moisture-absorbing medium for the presence of the inside of the container of a moisture-absorbing medium always has a lower humidity than in the external ambient atmosphere prevails, preference being given to moisture or damp Water is understood. For this purpose, a desiccant is preferred, as is known to the person skilled in the art is used. Silica gels, zeolites are very particularly preferred as drying agents or clays, optionally also combinations thereof.

In a particularly preferred embodiment, the moisture-absorbing medium firmly connected to the closable container or at least a part thereof. Most notably a desiccant is preferably integrated in the lid or stopper of a tube, such that a drying effect takes place only inside the tube. A Such a particularly preferred embodiment of the system according to the invention is shown in FIG 3 shown. Figure 3 shows a sample holder 1, which is sealed in a tube 2 with a closing plug 3 containing a desiccant 4 is introduced.

In a further preferred embodiment, the absorbent material of the system according to the invention contains one or more stabilizers for the sample material. It has been shown, for example, that sample material containing glycated protein, which is on an absorbent material, can be stored very well without substantial change in the content of glycated protein if the absorbent material is impregnated with boric acid buffer, pH greater than or equal to 10.5 or if the absorbent material carries a transition metal salt. The concentration of the boric acid buffer is of minor importance. Particularly good results are achieved if the boric acid buffer has a pH greater than or equal to 11. Suitable buffer concentrations are in the range between 300 and 1000 mmol / l, which corresponds to approximately 18.6-62 g / 100 ml. An analogous, well-stabilizing effect is exerted by transition metal salts, such as, for example, nickel or copper salts. Nickel salts are particularly preferred. Water-soluble transition metal salts are preferably used. Corresponding chlorides are well suited, for example. In order to have a sufficiently stabilizing effect, transition metal salt concentrations on the absorbent material of greater than 5 g / m ² , particularly preferably greater than 10 g / m ^{2, have} proven to be suitable.

The system according to the invention is suitable for storing and transporting sample material to be analyzed. Analytes that can be transported and stored in this way include glucose and glycosylated hemoglobin (HbA _1c ). In essence, however, each analyte can be supplied to a measurement that can be brought into solution by appropriate elution agents and that can then be measured in this solution. Basically, these are, for example, all analytes that can be determined using enzymatic, immunological and other test methods. Without wishing to limit the range of possible analytes, those analytes which are used to detect infectious diseases, such as virus antibodies or virus components for the determination of hepatitis and HIV, should also be mentioned here. Samples containing them can thus be advantageously transported to the analysis site. The use of a moisture-absorbing medium in the system according to the invention ensures safe handling by the end user, since the user does not have to pay attention to drying the sample before packaging the absorbent material containing the sample. Good stability of the sample material is also guaranteed.

The invention is explained further in the following example.

example 1 Stabilization of HbA _1c  on an absorbent material through a moisture absorbent medium

On a polyester film 3 with dimensions of 49 x 6 mm with a semicircular cut-out 5 by 5 mm at one short end is made using double sided tape 4 a first layer 1 of absorbent material, as shown in Figure 1, so on the Carrier film fixed that it is glued to the adhesive tape 4 with a width of 0.5 to 1 mm. The later removability is positively influenced by this relatively narrow fixation. The second layer 2 of absorbent material is glued to a width of 5 mm or more.

For the first layer of absorbent material, a nonwoven is made on a paper machine was used and has the following data:

80 parts of polyester fibers (fiber diameter 1.7 Dtex), 20 parts of viscose, 20 parts of polyvinyl alcohol; Basis weight 80 g / m ² ; Suction height 102 mm (DIN 53106).

This fleece was cut to size 6 x 6 mm. This matrix takes a quantity of liquid of approx. 10 µl

A fleece is used for the second layer of absorbent material, that of the first layer corresponds.

Probe 1

EDTA-Blut 9,5 % HbA_1c

Probe 2

EDTA-Blut 4,9 % HbA_1c

Probe 3

Probe 2 auf 400 mg/dl β-D(+)-Glukose aufgestockt

About 10 µl of EDTA blood (samples 1 to 3) are applied to elements manufactured in this way and contain an absorbent material and dried at room temperature for at least 2 hours.

Sample 1

EDTA blood 9.5% HbA _1c

Sample 2

EDTA blood 4.9% HbA _1c

Sample 3

Sample 2 increased to 400 mg / dl β-D (+) - glucose

To simulate a transport, the sample carriers are kept at 20, 35 and 45 ° C for 7 days at a humidity of 90% +/- 8%. Part of the sample carrier is in one conventional envelope, a second part in a sealed, borderable bag without Desiccant, a third part in a sealed, flirtable bag with a molecular sieve desiccant bag (Order number 1602080, Boehringer Mannheim GmbH, Germany), and a fourth part in a sealed tube containing molecular sieve (Order number 1775111, Boehringer Mannheim GmbH, Germany) as a drying agent.

After removing the first layer of absorbent material, the material is eluted in 1 ml of hemolysis reagent for the Tina-quant® test by Boehringer Mannheim GmbH (Germany) (order number 1 488 457) for 1.5 to 2.5 h. HbA _{1c is then} determined using the immunological determination method of Boehringer Mannheim GmbH (Germany) on a Hitachi 717 device from Boehringer Mannheim GmbH with reagent of the order number 1 488 414 from Boehringer Mannheim GmbH.

Table 1 summarizes the measurement results for elements in which storage was carried out with and without moisture-absorbing medium.

As a result, it can be seen that storage in a closed container, the one contains moisture-absorbing medium for such a stabilization of the non-enzymatic Glycosylated protein results in sufficiently unchanged even after exposure to temperature Concentration values are available.

Claims (15)

System for storing and transporting sample material on absorbent material characterized in that there are no test reagents in the system and it in addition to the absorbent material for absorbing liquid samples, a closable one Contains container with a moisture-absorbing medium. System according to claim 1, characterized in that the absorbent material auxiliary substances contains for spreading the sample. System according to claim 1, characterized in that the absorbent material is a Includes marking of the sample application zone. System according to claim 1, characterized in that the absorbent material with Handling instructions is provided. System according to claim 1, characterized in that it acts as a moisture absorbent Medium contains a desiccant. System according to claim 5, characterized in that it contains silica gels as drying agents, Contains zeolites or clays or any combination thereof. System according to claim 1, characterized in that the closable container consists of a tube closable with a stopper or lid. System according to claim 7, characterized in that the sealing plug or Lid and the tube from a dimensionally stable, shatterproof and with respect to the Sample inert material. System according to claim 8, characterized in that as the material for the tube Plastics, metals, alloys, paper or cardboard, optionally coated with one of the aforementioned materials, ceramics or glass can be used. System according to claim 9, characterized in that the tube made of polyethylene, Polypropylene or aluminum. System according to claim 1, characterized in that the moisture-absorbing Medium is firmly connected to the closable container or a part thereof. System according to claim 1, characterized in that the closable container is a flip envelope or bag. System according to claim 1, characterized in that the absorbent material attached to a carrier having a first and a second layer of absorbent material thus allowing itself to be touched on an inert carrier in a fluid transfer Contact arranged contains that liquid from the first to the second layer can reach when the first layer is filled with liquid and the first layer after application and drying of the sample material completely from the second Layer can be separated. System according to claim 1, characterized in that the absorbent material stabilizers contains for the sample. System according to claim 14, characterized in that to stabilize the sample the absorbent material with boric acid buffer, pH greater than or equal to 10.5, or one Transition metal salt is impregnated.

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