Abstrict Medical diagnostic test strips having a desiccant deposit applied
directly to the test strip. Moisture barrier sheets cover the test
strip. Alternatively, the moisture barrier sheets have a desiccant
deposit attached to them. Also alternatively, a pouch with a desiccant
deposit attached to its inner surface contains the test strip.
Claims What is claimed:
1. A medical diagnostic test strip package comprising:
(a) a medical diagnostic test strip having a top surface, a reagent
contained on a portion of said top surface, and a bottom surface;
and
(b) a first moisture barrier sheet adhered to said top surface
of said medical diagnostic test strip, said first moisture barrier
sheet having a desiccant deposit adhered to a portion thereof such
that said portion of said first moisture barrier sheet with said
desiccant deposit thereon is integrally disposed on said portion
of said medical diagnostic test strip containing said reagent.
2. A medical diagnostic test strip package as claimed in claim
1 further comprising a second moisture barrier sheet adhered to
said bottom surface of said medical diagnostic test strip.
3. A medical diagnostic test strip package as claimed in claim
1 wherein said desiccant is silica gel.
4. A medical diagnostic test strip package as claimed in claim
1 wherein said desiccant is molecular sieve.
5. A medical diagnostic test strip package as claimed in claim
1 wherein said desiccant is dispersed in a hot melt adhesive.
6. A medical diagnostic test strip package comprising:
(a) a medical diagnostic test strip having
(i) a top surface,
(ii) a reagent contained in a first portion of said top surface,
(iii) a desiccant deposit adhered to a second portion of said top
surface, said second portion adjacent to said first portion, and
(iv) a bottom surface; and
(b) a first moisture barrier sheet adhered to said top surface
of said medical diagnostic test strip.
7. A medical diagnostic test strip package as claimed in claim
6 further comprising a second moisture barrier sheet adhered to
said bottom surface of said medical diagnostic test strip.
8. A medical diagnostic test strip package as claimed in claim
6 wherein said desiccant is silica gel.
9. A medical diagnostic test strip package as claimed in claim
6 wherein said desiccant is molecular sieve.
10. A medical diagnostic test strip package as claimed in claim
6 wherein said desiccant is dispersed in a hot melt adhesive.
11. A medical diagnostic test strip package comprising:
(a) a medical diagnostic test strip having a top surface and a
reagent contained in a first portion of said top surface, and
(b) a pouch containing said medical diagnostic test strip, said
pouch having an inner surface and a desiccant deposit adhered to
a section of said inner surface, wherein said inner surface of said
pouch is disposed proximate said top surface of said medical diagnostic
test strip such that said desiccant deposit is adjacent to said
reagent of said test strip.
12. A medical diagnostic test strip package as claimed in claims
11 wherein said desiccant is silica gel.
13. A medical diagnostic test strip package as claimed in claim
11 wherein said desiccant is molecular sieve.
14. A medical diagnostic test strip package as claimed in claim
11 wherein said desiccant is dispersed in a hot melt adhesive.
15. A method of preventing water absorption by a medical diagnostic
test strip having a top surface, a bottom surface, and a portion
of said top surface containing a reagent, said method comprising
the steps of:
(a) covering said top surface with a first moisture barrier sheet;
(b) covering said bottom surface with a second moisture barrier
sheet; and
(c) integrally disposing a desiccant deposit in proximity to said
portion of said top surface of said medical diagnostic test strip
containing the reagent.
Description FIELD OF THE INVENTION
This invention relates to medical diagnostic test strips and, more
particularly, to a medical diagnostic test strip package having
a desiccant disposed in close proximity to the reagents on the test
strip such that single strip manufacturing, packaging, shipping,
and use is feasible.
BACKGROUND OF THE INVENTION
Medical diagnostic test strips are used in a variety of applications.
Such strips are exposed to samples of blood, feces, or urine, for
example, where specific reagents on the test strip are designed
to detect various components in the sample. Medical diagnostic test
strips are specifically used to detect the level of glucose in a
patient's blood. Such test strips must be exposed to an atmosphere
that is substantially moisture-free until moments before use in
testing a sample. The strips are often highly water absorbent, and
absorption of moisture may alter test results.
Accordingly, the known industry practice for keeping the test strips
dry is to contain a plurality of such test strips in a container
or vial. The cap for the container has a desiccant contained in
it to absorb water from the air inside the container. In this manner,
the strips within the container are kept dry. When ultimately used,
a doctor or other testing personnel, including a patient himself,
removes the cap from the container, extracts one of the test strips,
and immediately places it in the sample to be tested (or places
a small quantity of the sample to be tested on the test strip) Exposure
of the strips to the ambient atmosphere before use is thus minimized
to reduce water vapor absorption by the test strip.
A disadvantage of this technique is that all of the strips within
the vial must be used within a relatively short time after the vial
is first opened or they cannot be reliably used. The time period
is usually on the order of a few months. Because of the exposure
to the ambient atmosphere upon opening, there is a risk that the
test strips will absorb enough moisture to render them ineffective
in this amount of time despite the presence of the desiccant in
the cap. In addition, there are manufacturing, packaging, and use
complications resulting from the inclusion of multiple test strips
in a single vial according to prior practice. It is therefore desirable
to provide individual test strips with the ability to resist water
absorption. This would provide efficiencies in manufacturing, packaging,
and using the strips.
SUMMARY OF THE INVENTION
The present invention involves packaging individual test strips
such that the test strips remain in a moisture-free environment.
This is accomplished by applying a desiccant deposit directly to
the test strip and covering the test strip with moisture barrier
sheets, by using moisture barrier sheets having a desiccant deposit
attached to them, or by forming a pouch with a desiccant deposit
attached to an inner surface of the pouch and placing the test strip
within the pouch.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a perspective view of a first exemplary embodiment of
the present invention;
FIG. 2 is a perspective view of a second exemplary embodiment of
the present invention;
FIG. 3 is a partially cut-away perspective view of a third exemplary
embodiment of the present invention;
FIGS. 4 and 5 are perspective views of moisture barrier sheets
used in an exemplary embodiment of the present invention;
FIG. 6 is a perspective view of a reagent pad used with a test
strip in an exemplary embodiment of the present invention; and
FIG. 7 is a schematic view of a system for making a medical diagnostic
test strip package according to an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, individual medical diagnostic
test strips are packaged in a moisture-free environment by disposing
a desiccant in close proximity to the reagents used on the test
strip. FIG. 1 shows a first exemplary embodiment of the present
invention. In FIG. 1 test strip 10 is shown having reagent pad
11 attached to it. Reagent pad 11 contains the particular compounds
necessary to perform the desired detection test for a sample in
a particular application. In some cases, depending on the particular
reagents used, reagent pad 11 changes color upon exposure to the
test sample. This color change can be observed and possibly measured
to yield information regarding the presence or amount of the component
being measured. In other cases, other measurable or observable characteristics
of reagent pad 11 such as reflectance, may change upon exposure
to the test sample and thereby yield the desired information regarding
the sample.
Exemplary test strips and reagent pads used to measure the amount
of glucose in the blood, and the manufacture and use of such test
strips and reagent pads, are described in U.S. Pat. Nos. 4935346;
5049487; and 5304468 all of which are hereby incorporated by
specific reference for their teachings on the manufacture and use
of test strips and reagent pads.
Alternatively, reagent pad 11 may have the structure shown in FIG.
6. In FIG. 6 upper liner 60 is typically formed of polyethylene
terephthalate (or PET) and has a conventional cold or hot melt adhesive
on its bottom surface 64. A reagent paper layer 61 having the required
reagents for a particular application on it, is adhered to bottom
surface 64 of upper liner 60. A double-sided tape layer 62 is used
to adhere reagent paper layer 61 to lower liner 63 which is typically
formed of PET. After assembly of the composite layers shown in FIG.
6 reagent pad 11 is adhered to test strip 10 by conventional cold
or hot melt adhesives placed around the edges of upper surface 65
of upper liner 60. Test strip 10 has a hole 19 formed in it to access
reagent pad 11.
The top surface 12 of test strip 10 has a top sheet 13 adhered
to it. Top sheet 13 is adhered to test strip 10 by any conventional
cold adhesive or hot melt adhesive known in the art. FIG. 4 shows
an exemplary construction for top sheet 13. In FIG. 4 top sheet
13 is shown to have a two-part composite structure. Upper composite
layer 40 is formed of foil to provide a moisture barrier. Upper
composite layer 40 has a conventional cold or hot melt adhesive
on its bottom surface 42. The adhesive is used to attach upper composite
layer 40 to a lower composite layer 41.
Lower composite layer 41 is a microperforated layer typically made
of parchment paper or Mylar.RTM. film. Lower composite layer 41
also has a conventional cold or hot melt adhesive on its bottom
surface 43 to attach lower composite layer 41 (and hence top sheet
13) to test strip 10. Lower composite layer 41 has a desiccant deposit
14 adhered to it. Desiccant deposit 14 comprises a silica gel (or
other particle remover such as a molecular seive or an oxygen absorber)
dispersed in a medium suitable for suspending the silica gel and
allowing adhesion of desiccant deposit 14 to lower composite layer
41. In the exemplary embodiment shown, the medium comprises vinyl
acetate and a hot melt adhesive. As shown in FIG. 1 desiccant deposit
14 is located within top sheet 13 such that, upon application of
top sheet 13 to test strip 10 desiccant deposit 14 is adjacent
to reagent pad 11.
FIG. 1 shows a bottom sheet 15 adhered to the side of test strip
10 opposite upper surface 12. Bottom sheet 15 has an exemplary construction
shown in FIG. 5. In FIG. 5 lower composite layer 50 is made of
foil and forms a moisture barrier. Upper surface 52 of lower composite
layer 50 has a conventional cold or hot melt adhesive on it to adhere
lower composite layer 50 to upper composite layer 51. Upper composite
layer 51 is a microperforated layer typically formed of parchment
paper or Mylar.RTM. film, and has an upper surface 53 with a conventional
cold or hot melt adhesive on it to adhere upper composite layer
51 (and hence bottom sheet 15) to test strip 10.
Top sheet 13 and bottom sheet 15 are moisture barriers that prevent
any water from contacting, and being absorbed by, test strip 10.
In the event that test strip 10 is exposed to any moisture, desiccant
deposit 14 absorbs the moisture rather than reagent pad 11. Desiccant
deposit 14 may also alternatively be applied to bottom sheet 15
or to both top sheet 13 and bottom sheet 15.
Test strip 10 with top sheet 13 and bottom sheet 15 adhered to
it and with desiccant deposit 14 in top sheet 13 may be manufactured
and shipped individually, along with other test strips. An exemplary
manufacturing process is schematically illustrated in FIG. 7. As
shown in FIG. 7 press rolls may be used to produce a test strip
package according to the present invention. Roll 70 is a rolled
length of the composite reagent pad 11 described in connection with
FIG. 6 Roll 71 is a rolled length of polyvinylchloride (or PVC)
strip stock of which test strip 10 may be formed. Roll 70 is unwound
and cut into reagent pads 11 of appropriate size. Reagent pads 11
are then pressed onto PVC test strip material unwound from roll
71. Simultaneously, roll 73 of a length of upper sheet 13 and roll
72 of a length of bottom sheet 15 are unwound, and sheets 13 and
15 are pressed onto the top surface 12 and the bottom surface 16
respectively, of the length of test strip material with reagent
pads 11.
To use test strip 10 the doctor or other testing personnel peels
off top sheet 13 and bottom sheet 15 much like with a Band-Aid.RTM.
bandage, and inserts test strip 10 into a sample for testing (or
places the sample on test strip 10).
FIG. 2 illustrates a second embodiment of the present invention.
In FIG. 2 test strip 10 has desiccant deposit 14 applied directly
to it. Desiccant deposit 14 has the same composition as described
in connection with the exemplary embodiment of FIG. 1. With the
exemplary embodiment shown in FIG. 2 top sheet 22 and bottom sheet
23 are applied to the top and bottom surfaces 12 and 16 respectively,
of test strip 10. Top sheet 22 and bottom sheet 23 are moisture
barriers, and may have a composite construction as described in
connection with bottom sheet 15 in the exemplary embodiment of FIG.
5.
In use, top sheet 22 and bottom sheet 23 are peeled away from test
strip 10 by the doctor or other testing personnel. Test strip 10
with desiccant deposit 14 adhered thereto, is then inserted into
the sample for testing (or the sample is placed on reagent pad 11
of test strip 10).
Alternatively, desiccant deposit 14 may comprise a hot melt adhesive
with a desiccant dispersed in it. Any known hot melt adhesive and
desiccant can be used for this purpose. The adhesive may serve an
adhesive function, for example, to help secure top sheet 22 or bottom
sheet 23 to test strip 10 Alternatively, the adhesive may be allowed
to dry before application of top sheet 22 or bottom sheet 23 and
serve only as a carrier for the desiccant and not as an adhesive.
FIG. 3 illustrates a third embodiment of the present invention.
In FIG. 3 test strip 10 with reagent pad 11 is shown with a pouch
32 which is designed to contain test strip 10. Pouch 32 is formed
of top sheet 33 and bottom sheet 34 which are adhered together along
three of their edges to form seals 35 36 and 37. The remaining
edge of top sheet 33 and bottom sheet 34 on one side of the pouch
is closed using a reclosable ziplock opening 38. Reclosable ziplock
opening 38 allows access to the interior of pouch 32. Desiccant
deposit 14 is formed on the inside of the pouch on top sheet 33
bottom sheet 34 or both. Desiccant deposit 14 may have the same
composition as described above in connection with FIG. 1. Top sheet
33 and bottom sheet 34 are moisture barriers that may have the composite
structure described for bottom sheet 15 in connection with FIG.
5. In use, the doctor or other testing personnel opens reclosable
ziplock opening 38 and removes test strip 10. Test strip 10 is then
immediately placed in a sample for testing (or the sample is placed
on reagent pad 11 of test strip 10).
Alternatively, desiccant deposit 14 may comprise a hot melt adhesive
with a desiccant dispersed in it. Any known hot melt adhesive and
desiccant can be used for this purpose. The adhesive may serve an
adhesive function, for example, to help secure top sheet 33 or bottom
sheet 34 of pouch 32 to the test strip. The adhesive also may be
allowed to dry before insertion of test strip 10 into pouch 32 and
serve only as a carrier for the desiccant and not as an adhesive. |