Patent Application
20100173423
The present invention relates to a multiple testing apparatus and method for concurrently performing two or more strip-format assays on a single sample.
Lateral flow test strips have become increasingly popular over the last thirty years as means for rapid detection of specific constituents in a variety of specimens, including bodily fluids such as urine, saliva, serum, plasma and whole blood. A lateral flow test strip is typically constructed from one or more porous membranes impregnated with assay-specific reagents. To perform a test, a sample is applied to one end of the test strip, referred to as the sample receiving zone. The sample is drawn through the strip by capillary action to pass through a reaction zone where the analyte, when present, reacts with the pre-impregnated assay-specific reagents and then proceeds into a detection zone where the appearance of a visible or otherwise detectable signal indicates presence of the analyte in the sample. Typically, test strips further include an internal procedural control line that is used to validate the test result. Appearance of two lines, therefore, indicates a positive result, while a negative test results in only one line. There exist many variations of test strips, regarding the materials from which the strip is constructed, the distribution and nature of the pre-impregnated reagents and their interaction with the analyte, as well as to the nature and formation of the signal.
Test strips can be used for qualitative or semi-quantitative analysis of many analytes including analytes of clinical interest such as antigens, antibodies, proteins, hormones, enzymes and nucleic acids. The sensitivity and specificity of many available test strips has been shown to be sufficient for clinical diagnostic purposes and therefore they are widely used by medical staff, or as self-testing at home, for rapid diagnosis and therapeutic monitoring of various conditions and disorders.
It is often desired to perform more than one assay on the same sample for detecting two or more independent analytes which indicate two or more different diseases or conditions, or for detecting two or more analytes which are associated with the same disease or condition. For example, it may be desirable to simultaneously detecting an antigen and an antibody which are associated with same pathogen, in order to provide better diagnosis.
However, collected samples can be of a limited volume, thus limiting the number of analyses that can be performed. Moreover, an excess amount of sample is required due to losses such as evaporation and adherence of parts of the sample to the walls of the vessel or of the sample transferring device. Additionally, a major importance in comparing different test results of the same sample is that the tests are performed under the same conditions (e.g. temperature, humidity). Thus, the time of the analysis and the environmental parameters can be of vital importance when comparing the results of various analyses of the same specimen. Consequently, personnel handling parallel tests try to economize and calculate the number of aliquots that can be taken from a sample, and make the best efforts to perform each analysis under the same conditions. However these efforts require high skills and often provide only similar, but not identical, conditions due to the fact that the tests are not done concurrently and with the same aliquot.
There is therefore a need for apparatus and method that will allow for conducting a number of tests on a single sample under identical conditions for improving accuracy of analysis. There is a further need to provide such an apparatus and method that will allow for performing a number of tests on a single sample with minimum loses and in a simple and straightforward manner.
The present invention provides a multiple testing method and apparatus for analyzing one or more analytes in a sample by using a plurality of test strips. The apparatus comprises at least two test strips overlaid on a non-bibulous planar support and arranged in contact with a common sample application site. The configuration of the multiple testing apparatus provides that subsequently to the application of a sample in the sample application site, portions of the sample are absorbed by the bibulous receiving ends of the strips and are drawn by capillary forces to advance along the strips toward the opposite end thereof.
The common application site is a defined area of the non-bibulous support delimited by a liquid impervious barrier. The liquid impervious barrier may be a line or an area of hydrophobic material affixed to said planar support or, alternatively, may be an elevated wall. The hydrophobic material may be selected from a group consisting of wax, paraffin, oil, crayon, hydrophobic ink, hydrophobic glue or any other hydrophobic material that may be affixed to the planar support. The common application site may be formed as a depression on the non-bibulous support or may be formed by cutting an opening in a non-absorbent film attached onto the planar support.
According to some embodiments, at least a portion of the sample receiving pad of each of the at least two test strips overlaps said sample application site. Yet in accordance with other embodiments, the sample receiving pads of the test strips may be in tangent contact with the sample application site.
The two or more test strips may be arranged in a parallel or a non-parallel configuration. The test strips may be any test strips adapted for detecting an analyte in a liquid sample by a lateral flow assay including qualitative test strips, semi-quantitative test strips and quantitative test strips. The sample may be any liquid sample including bodily liquids such as blood, serum, plasma, urine and bodily secretion.
The invention also relates to a method for concurrently performing two or more test strip assays on a single sample. The method comprises: providing a non-bibulous planar support; placing two or more test strips on the non-bibulous planar support; forming a liquid impervious barrier to define a sample application site in contact with the sample receiving pads of each of the test strips; and applying a sample in said sample receiving site. The method may further comprise adding a reagent solution to the sample application site.
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
The present invention discloses a multiple assay apparatus and method for simultaneously performing two or more tests on a single sample by splitting the sample between two or more test strips. The apparatus comprises at least two test strips arranged in contact with a common sample application site. The configuration of the multiple testing apparatus allows for distributing aliquots of the sample between the test strips, thereby sample aliquots advance through the individual strips by capillary forces. Depending on the specific design of the test strips employed, the multiple test results may be visible color signals that can be detected by the naked eye, or alternatively may be read with the aid of an external reading instrument, employing optical reflectance or transmission. The volume of the sample added to the sample application site is measured as the total sum of the individual amounts required for each of the multiple test strips.
The two or more test strips may be identical test strips or different test strips designed for detecting the same analyte, or may be different test strips designed for detecting different analytes. For example, one test strip may be a test strip designed for the detection of an antigen which is associated with a viral or bacterial pathogen and a second test strip may be a test strip designed for the detection of an antibody which is associated with the immunological response to that pathogen.
Referring to
Sample application site 40 is defined by floor 41 of base 50 and by wall 39 which is formed by the cut in film 35, as demonstrated in
Test strips 20 and 30 may be selected to be any test strip known in the art which is designed for detecting an analyte in a liquid sample by a lateral flow assay, including immunoassays, enzymatic assays, biochemical assays and chemical assays. Test strips 20 and 30 comprise a sample receiving pad 60, 61, a reaction zone 62, 63, a detection zone 68, 69 and absorbent wick 70, 71, respectively. Detection zones 68, 69 comprise a test signal line 64t, 65t and a control line 66c, 67c respectively. Test strips 20, 30 may be constructed from one or more bibulous or non-bibulous porous solid phase materials arranged sequentially in an abutting or partial overlapping manner to form a fluid communication therebetween. The strips may be supported on a backing support and/or laminated between two impermeable non-absorbing films such as mylar films, at least one of which is transparent or translucent for allowing viewing the signal. It will be realized that the particular structure of the test strips shown here is given by way of illustration only and that other test strips of different structures may be used without departing from the scope of the present invention.
Strips 20 and 30 are placed on base 50 and partially on film 35 such that one corner 21, 31 of the test strip's sample receiving end overlaps, or is in tangent contact with, sample application site 40. Thus when a liquid sample is added to sample application site 40, the liquid cannot spread beyond wall 39 but can only be absorbed by the test strips. In other words, wall 39 prevents the liquid from advancing to any direction except toward bibulous test strips 20 and 30. The sample is thus spontaneously taken by the naturally hydrophilic individual test strips to advance by capillary forces from the sample receiving end 60, 61 toward wick 70, 71.
To perform a test, a liquid sample is added to sample application site 40, thereafter portions of the sample are drawn concurrently by capillary action into test strips 20 and 30. Thus, the sample is divided between the two test strips and each respective portion advances from the respective sample receiving end 60, 61 through respective reaction zones 62, 63 and further through respective detection zone 68, 69, to opposite respective end 70, 71. The required volume of the sample is substantially the total sum of the individual amounts required for each of the multiple test strips. If an additional reagent solution is required in order to perform the test, the required solution may be added to sample application site 40 before or after the sample as required by the test procedure. Thus, apparatus 10 provides for concurrently running two tests on the same sample under identical conditions. The concurrent tests provide for reduced labor, reduced sample waste and ensures that the tests are actually parallel, thus minimizing the effect of external interfering factors that can influence parallel test analysis.
It will be realized that the layout of the test strips around the common application site as well as the contact border or contact area between the test strips and the common application site may assume different configurations. Similarly, the shape of the common application site is not limited to a circular shape, but may assume other shapes as well. It will be also realized that the contact area between the individual test strips and the common sample application site is not necessarily the same for all strips. Thus, when different volumes of aliquots are required for different test strips, the contact border or contact area between the individual strips and the sample application site may be manipulated so as to provide the desired ratio between the different aliquots.
It will be appreciated that the above exemplary embodiments are given for the sake of demonstration only and that many other variations of the present apparatus, regarding the number and layout of the test strips and the outline and area of the common sample application site, may exist without departing from the scope of the present invention.
Two Determine® HIV and HBsAg test devices were obtained from Inverness Medical Innovations, Inc., Waltham, Mass., USA. The protective cover was removed from the test devices and the test strips were peeled from the back panel of the devices. The strips were then attached side-by side to the one of the back panels of one of the now empty devices. The distance between the strips was 2 mm. Employing a wax pencil, lines were drawn between the strips at either end of the sample receiving pads of the strips according to the embodiment of
As in Example 1, two Determine® strips were peeled off from their devices. A 5mm diameter hole was created in a 10×10 mm piece of polyethylene film with adhesive backing. The piece was attached to the back panel of the now empty Determine® device and the two strips were attached on top of the hole according to the embodiment of
Persons skilled in the art will appreciate that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims, which follow.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
