Note: Descriptions are shown in the official language in which they were submitted.
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Title: Optical Arrangement for Assay Reading Device
Field of the Invention
The present invention relates to assay reading devices for the measurement of
analytes. In
particular it relates to electronic readers for use with assay test-strips
which use optical
methods of measurement.
Background of the Invention
Disposable analytical devices suitable for home testing of analytes are now
widely
commercially available. A lateral flow immunoassay device suitable for this
purpose for the
measurement of the pregnancy hormone human chorionic gonadotropin (hCG) is
sold by
Unipath under the brand-name CLEARBLUE and is disclosed in EP291194.
EP291194 discloses an immunoassay device comprising a porous carrier
containing a
particulate labelled specific binding reagent for an analyte, which reagent is
freely mobile
when in the moist state, and an unlabelled specific binding reagent for the
same analyte,
which reagent is immobilised in a detection zone or test zone downstream from
the
unlabelled specific binding reagent. Liquid sample suspected of containing
analyte is applied
to the porous carrier whereupon it interacts with the particulate labelled
binding reagent to
form an analyte-binding partner complex. The particulate label is coloured and
is typically
gold or a dyed polymer, for example latex or polyurethane. The complex
thereafter migrates
into a detection zone whereupon it forms a further complex with the
immobilised unlabelled
specific binding reagent enabling the extent of analyte present to be
observed.
However such commercially available devices as disclosed above require the
result to be
interpreted by the user. This introduces a degree of subjectivity, which is
undesirable.
Electronic readers for use in combination with assay test-strips for
determining the
concentration and/or amount of analyte in a fluid sample are known. EP653625
discloses
such a device which uses an optical method in order to determine the result.
An assay test
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strip such as that disclosed in EP291194 is inserted into a reader such that
the strip is aligned
with optics present within the reader. Light from a light source, such as a
light emitting
diode (LED), is shone onto the test strip and either reflected or transmitted
light is detected
by a photodetector. Typically, the reader will have more than one LED, and a
corresponding
photodetector is provided for each of the plurality of LED's.
US5580794 discloses a fully disposable integrated assay reader and lateral
flow assay test
strip whereby optics present in the reader enable the result to be determined
optically using
reflectance measurements.
An important consideration in assay reading devices of this type is the
requirement that the
assay reader and the test strip are carefully aligned. This is because the
visible signal formed
in the detection zone (and the control zone, if present) is fairly narrow
(about lmm wide), so
a small displacement of the detection or control zone relative to the
respective photodetector
may significantly affect the reading made by the photodetector. In addition,
it is generally
important that the photodetector is as close as possible to the test strip,
because the amount
of light which is 'captured' by the photodiode is fairly small, and the signal
intensity
normally obeys the inverse square law, so that it diminishes rapidly as the
separation
between the test strip and the photodetector increases. Thus there is a
requirement for the
user to carefully align the test stick with the assay result reader which,
especially for devices
intended to be used in the home, can be problematic.
One solution to this problem is provided by US 5580794, wherein the assay
strip is provided
as an integral component of the result reader, thereby avoiding the need for
the user to insert
the test strip into the reader. An alternative solution is taught by EP
0833145, which
discloses a test strip and assay result reader combination, wherein the assay
result reading
device can be successfully triggered to make a reading only when there is a
precise three-
dimensional fit between the test strip and the reader, thereby ensuring the
correct alignment
has been obtained.
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Summary of the Invention
The present disclosure provides typically disposable, assay readers either for
use with, or in
integral combination with, an assay test strip such as disclosed by EP291194.
In one aspect, the present invention provides an assay result reading device
for reading the
result of an assay performed using a test strip, comprising first, second and
third light
sources capable of emitting light for illuminating respective first, second
and third spatially
separated zones of the test strip. The device also includes first and second
photodetectors,
wherein the first photodetector detects light emanating only from each of the
first and second
zones and the second photodetector detects light emanating only from each of
the second and
third zones.
In another aspect, the invention provides a method of determining the result
of an assay
performed using a test strip, the method comprising: positioning the test
strip in relation to
an assay result reader comprising a housing enclosing first, second and third
light sources to
illuminate the test strip; and measuring a light level received by first and
second
photodetectors in the assay result reader;
wherein, the test strip is so positioned relative to the assay result reader
that the
first, second and third light sources emit light incident on respective first,
second and third
spatially separated zones of the test strip, and so that light emanating only
from the first and
second zones is incident on the first photodetector and light emanating only
from the second
and third zones is incident on the second photodetector.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a perspective view of an assay result reader;
Figure 2 is a block diagram illustrating schematically some of the internal
components of the
reading device embodiment depicted in Figure 1;
Figure 3 is a plan view of certain internal components showing an embodiment
of one
arrangement;
Figure 4 is a plan view showing an arrangement of certain internal components;
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Figure 5 is an elevation view of certain internal components showing an
embodiment of one
arrangement and exemplary optical paths;
Figure 6 is an exploded top perspective view of a baffle element and a circuit
board of an
exemplary embodiment;
Figure 7 is a top plan view showing an exemplary baffle arrangement;
Figure 8 is a bottom perspective view showing an exemplary baffle arrangement;
Figure 9 is a bottom plan view showing an exemplary baffle arrangement;
Figure 10 is an exploded cross-sectional side view taken at line 10-10 in
Figure 7 showing
an exemplary baffle arrangement, circuit board, and a test strip; and
Figure 11 is a transverse cross-sectional view taken at line 11-11 in Figure
10 showing an
exemplary baffle arrangement and a test strip.
DETAILED DESCRIPTION
The optical arrangements for assay readers described herein promote simplicity
and
economy. The manufacturing cost of the device is an especially important
consideration if
the reader is intended to be disposable; the photodetectors themselves, being
relatively
expensive components, form a significant part of the overall cost.
A further advantage is that the arrangement can provide greater accuracy and
reduce the
need for accurate positioning of the test strip relative to the reader.
Suppose, for example, a
test strip were provided with two separate, but closely spaced, control zones
and a
photodetector were positioned in the reader so as to be between the two
control zones. If the
test strip were slightly misaligned, laterally, relative to the assay reader
device, the signal
from one of the control zones would be less intense as the zone in question
would be further
from the photodetector. However, the other control zone would necessarily be
closer to the
photodetector by a corresponding amount, and would therefore provide a
stronger signal to
compensate for the weaker signal from the other zone. Furthermore it has been
observed
that the amount of bound material present at a particular zone will vary along
the length of
the zone in the direction of liquid flow. Preferential binding of the analyte
takes place at the
leading boundary edge and diminishes along the length of the zone in the
direction of liquid
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flow. Thus any misalignment may result in a greater error than might have been
expected if
the analyte were captured in a uniform fashion. US 5968839 discloses an
electronic assay
reader for use with a test strip, wherein it is attempted to compensate for
this non-uniform
binding by the provision in the relevant binding zone of a plurality of
deposits of
immobilised capture reagent, the density of which deposits increases from the
leading
boundary to the trailing edge of the zone.
Similarly, some of the arrangements described herein also reduce the
requirement for precise
relative positioning of the test strip and the assay result reading device:
there is an in-built
signal compensation for any misalignment between the test strip and the assay
result reader
for any zone which is commonly read by the two or more photodetectors, because
relative
movement of the commonly read zone away from one of the photodetectors will
necessarily
(within certain limits) involve movement by a corresponding amount towards the
other
photodetector/s.
The light emanating from the zone or zones, as appropriate, may be light which
is reflected
from the test strip or, in the case of a test strip which is transparent or
translucent (especially
when wet e.g. following the application of a liquid sample), light which is
transmitted
through the test strip. For the purposes of the present specification, light
incident upon a
particular zone of a test strip from a light source, and reflected by the
strip or transmitted
therethrough, may be regarded as "emanating" from the strip, although of
course the light
actually originates from the light source.
The preferred light sources are light emitting diodes (LED's), and the
preferred photodetector
is a photodiode.
Reflected light and/or transmitted light may be measured by the photodetector.
For the
present purposes, reflected light is taken to mean that light from the light
source is reflected
from the test strip onto the photodetector. In this situation, the detector is
typically provided
on the same side of the test strip as the light source. Transmitted light
refers to light that
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passes through the test strip and typically the detector is provided on the
opposite side of the
test strip to the light source. For the purposes of a reflectance measurement,
the test strip
may be provided with a backing such as a white reflective MYLAR plastic
layer. Thus
light from the light source will fall upon the test strip, some will be
reflected from its surface
and some will penetrate into the test strip and be reflected at any depth up
to and including
the depth at which the reflective layer is provided. Thus, a reflectance type
of measurement
may actually involve transmission of light through at least some of the
thickness of the test
strip. Generally, measurement of reflected light is preferred.
It is especially preferred that the reading device of the second aspect
comprises a plurality of
light sources, each light source being incident upon a respective zone of the
test strip.
In principle, an assay result reading device in accordance with the present
disclosure may
comprise any number of light sources and any number of photodetectors. For
example, one
embodiment includes three light sources, each illuminating a respective zone
of a test strip,
and a single photodetector which is shared by all three zones. In practice it
is difficult to
arrange for more than three zones to share a single photodetector, because the
photodetector
will have trouble in detecting a sufficiently strong signal from those zones
which are furthest
away.
In preferred embodiments, an assay result reader feature both "shared"
photodetectors as
well as "commonly read" zones; i.e., a single photodetector can receive light
emanating from
more than one zone, and light emanating from a single zone is received by more
than one
photodetector. In this instance, the reader will typically include a plurality
of light sources
and a smaller plurality of photodetectors. In particular, where the reader
comprises x light
sources for illuminating the test strip, it will comprise x-1 photodetectors.
The number of
detectors required might be reduced still further by sharing of the
photodetectors between the
respective light sources, e.g. using three photodetectors to detect light
emanating from an
assay test strip that has been illuminated by five light sources.
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More specifically, a preferred embodiment of an assay result readers includes
first, second
and third light sources, each light source illuminating respective first,
second or third zones
of a test strip. Conveniently the first light source illuminates a test zone
or detection zone;
the second light source illuminates a reference zone; and the third light
source illuminates a
control zone. The test or detection zone is a zone of the test strip in which
an optical signal
is formed (e.g. accumulation or deposition of a label, such as a particulate
coloured binding
reagent) in the presence or absence, as appropriate, of the analyte of
interest. (By way of
explanation some assay formats, such as displacement assays, may lead to the
formation of
signal in the absence of the analyte of interest). The control zone is a zone
of the test strip in
which an optical signal is formed irrespective of the presence or absence of
the analyte of
interest to show that the test has been correctly performed and/or that the
binding reagents
are functional. The reference zone is a zone wherein, typically, only
"background" signal is
formed which can be used, for example, to calibrate the assay result reading
device and/or to
provide a background signal against which the test signal may be referenced.
In this particular preferred embodiment, the reader also includes two
photodetectors. The
first photodetector is substantially adjacent to or primarily associated with
the first light
source and is intended to detect light emanating the zone of the test strip
illuminated by the
respective light source. However, the photodetector is so positioned as to be
also capable of
detecting some of the light emanating from the second zone of the test strip,
illuminated by
the second light source.
The second photodetector is substantially adjacent to or primarily associated
with the third
light source and is intended to detect light emanating from the zone of the
test strip
illuminated by the respective light source. However the photodetector is so
positioned as to
be also capable of detecting some of the light emanating from the second zone
of the test
strip, illuminated by the second light source.
Accordingly, this embodiment features a "shared" photodetector, because it
includes a
plurality of light sources and a photodetector which detects light emanating
from at least two
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spatially separated zones of the test strip. In addition, this embodiment has
"commonly
read" zones, because it comprises two photodetectors, both of which are able
to detect some
of the light emanating from a zone of the test strip (in this instance, two
photodetectors are
able to detect light emanating from the second zone of the test strip).
It is preferred that, when the assay strip is correctly inserted into a reader
device, a
commonly read zone will be at a position intermediate between the two
photodetectors, such
that (within certain limits) a lateral movement away from one of the
photodetectors will
inevitably involve a corresponding lateral movement towards the other
photodetectors, so as
to allow for the desired signal compensation effect. Typically, but not
essentially, the
commonly read zone will be approximately equidistant from the two
photodetectors when
the test strip is correctly positioned within the reader.
It is also preferred that, where an assay result reading device includes a
plurality of light
sources, these are advantageously arranged such that a particular zone is
illuminated only by
a single one of the plurality of light sources. For example, optical baffles
may be provided
between or around the light sources so as to limit the portion of the test
strip illuminated by
each light source.
For the avoidance of doubt, it is expressly stated that any features described
as "preferred",
"desirable", "convenient", "advantageous" or the like may be adopted in an
embodiment of
an assay result reader in combination with any other feature or features so-
described, or may
be adopted in isolation, unless the context dictates otherwise.
EXAMPLES
A number of Examples are provided to illustrate selected aspects and
embodiments of the
disclosed subject matter. These Examples merely provide instantiations of
systems, devices,
and/or methods and are not intended to limit the scope of the disclosure.
Example 1
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An embodiment of an assay result reading device having both "shared"
photodetectors and
"commonly read" zones is illustrated in Figure 1.
The reading device is about 12cm long and about 2cm wide and is generally
finger or cigar-
shaped. In preferred embodiments, the housing is no larger than about 12 cm
long, about 2.5
cm wide, and about 2.2 cm tall. However, any convenient shape may be employed,
such as
a credit card shaped reader. The device comprises a housing 2 formed from a
light-
impermeable synthetic plastics material (e.g. polycarbonate, ABS, polystyrene,
high density
polyethylene, or polypropylene or polystyrol containing an appropriate light-
blocking
pigment, such as carbon). At one end of the reading device is a narrow slot or
aperture 4 by
which a test strip (not shown) can be inserted into the reader.
On its upper face the reader has two oval-shaped apertures. One aperture
accommodates the
screen of a liquid crystal display 6 which displays information to a user e.g.
the results of an
assay, in qualitative or quantitative terms. The other aperture accommodates
an eject
mechanism actuator 8 (in the form of a depressible button), which when
actuated, forcibly
ejects an inserted assay device from the assay reading device.
The test strip for use with the reading device is a generally conventional
lateral flow test
stick e.g. of the sort disclosed in US 6,156,271, US 5,504,013, EP 728309, or
EP 782707.
The test strip and a surface or surfaces of the slot in the reader, into which
the test strip is
inserted, are so shaped and dimensioned that the test strip can only be
successfully inserted
into the reader in the appropriate orientation.
When a test strip is correctly inserted into the reader, a switch is closed
which activates the
reader from a "dormant" mode, which is the normal state adopted by the reader,
thereby
reducing energy consumption.
Enclosed within the housing of the reader (and therefore not visible in Figure
1) are a
number of further components, illustrated schematically in Figure 2.
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Referring to Figure 2, the reader comprises three LED's 10a, b, and c. When a
test strip is
inserted into the reader, each LED 10 is aligned with a respective zone of the
test strip. LED
10a is aligned with the test zone, LED 10b is aligned with the reference zone
and LED 10c is
aligned with the control zone. Two photodiodes 12 detect light reflected from
the various
zones and generate a current, the magnitude of which is proportional to the
amount of light
incident upon the photodiodes 12. The current is converted into a voltage,
buffered by
buffer 14 and fed into an analogue to digital converter (ADC, 16). The
resulting digital
signal is read by microcontroller 18.
One photodiode detects light reflected from the test zone and some of the
light reflected
from the reference zone. The other photodiode 12 detects some of the light
reflected from
the reference zone and the light reflected from the control zone. The
microcontroller 18
switches on the LED's 10 one at a time, so that only one of the three zones is
illuminated at
any given time ¨ in this way the signals generated by light reflected from the
respective
zones can be discriminated on a temporal basis.
Figure 2 further shows, schematically, the switch 20 which is closed by
insertion of an assay
device into the reader, and which activates the microcontroller 18. Although
not shown in
Figure 2, the device further comprises a power source (typically a button
cell), and an LCD
device responsive to output from the microcontroller 18.
In use, a dry test strip (i.e. prior to contacting the sample) is inserted
into the reader, this
closes the switch 20 activating the reader device, which then performs an
initial calibration.
The intensity of light output from different LED's 10 is rarely identical.
Similarly, the photodetectors 12 are unlikely to have identical sensitivities.
Because such
variation could affect the assay reading an initial calibration is effected,
in which the
microcontroller adjusts the length of time that each of the three LED's is
illuminated, so that
the measured signal from each of the three zones (test, reference and control)
is
approximately equal and at a suitable operating position in a linear region of
the response
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profile of the system (such that a change in intensity of light reflected from
the various zones
produces a directly proportional change in signal).
After performing the initial calibration, the device performs a further, finer
calibration. This
involves taking a measurement ("calibration value") of reflected light
intensity for each zone
whilst the test strip is dry ¨ subsequent measurements ("test values") are
normalised by
reference to the calibration value for the respective zones (i.e. normalised
value = test
value/calibration value).
To conduct an assay, a sample receiving portion of the test strip is contacted
with the liquid
sample. In this case of a urine sample for instance, the sample receiving
portion may be held
in a urine stream, or a urine sample collected in a receptacle and the sample
receiving
portion briefly (about 5-10 seconds) immersed in the sample. Sampling may be
performed
whilst the test strip is inserted in the reader or, less preferably, the strip
can be briefly
removed from the reader for sampling and then reintroduced into the reader.
Measurements of reflected light intensity from one or more (preferably all
three) of the zones
are then commenced, typically after a specific timed interval following
insertion of the test
strip into the reader. Desirably the measurements are taken at regular
intervals (e.g. at
between 1-10 second intervals, preferably at between 1-5 second intervals).
The
measurements are made as a sequence of many readings over short (10
milliseconds or less)
periods of time, interleaved zone by zone, thereby minimising any effects due
to variation of
ambient light intensity which may penetrate into the interior of the reader
housing.
Example 2
This example described in greater detail the features of the preferred
arrangement of LED's
and photodiodes outlined in Example 1.
Figure 3 shows a plan view of an exemplary embodiment of an optical
arrangement. In this
embodiment, the optical arrangement include three light emitting diodes and
two
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photodetectors. The active area (A) of the photodetectors (PD) is 1.5mm x
1.5mm. The
optics are arranged such that center lines of LED's 1 and 3 correspond to the
center lines of
PD 1 and PD2. The 3 LED's and two photodetectors are disposed within an area
no larger
than about 1 square cm, preferably no larger than about 0.7 square cm,
specifically 1 cm x
0.7 cm.
Also shown is the position of the test-strip 30 that is positioned above the
LED's. The test-
strip is inserted so that the test and control lines 32 are situated above
respectively LED's 1
and 3. The distance D, namely the distance between the PD and LED, is
preferably large
enough to prevent specular reflection of light emitted from the LED from the
surface of the
test-strip directly to the PD. This distance will be dependent upon various
factors such as the
size of the windows, as well as the distance between the windows and the LED's
and will be
best determined by routine experimentation. The windows are situated above the
respective
LED's that effectively define the areas through which light shines. In one
exemplary
embodiment, the dimensions of the window are 2mm wide by 2.75mm high.
Figure 4 is a schematic representation of the layout of the 3 LED/2 Photodiode
optical
system described in Example 1.
Figure 4 depicts an optics block component for accommodation within an assay
result
reading device that includes three LED's (LED 1, 2 and 3) and two
photodetectors (PD1 and
PD2). Light from LED 1 illuminates a test zone of a test strip (not shown)
inserted into the
reader. Light reflected from the test zone is detected by PD1. Light from LED3
illuminates
a control zone of the test strip and light reflected therefrom is detected by
PD2. Light from
LED2 illuminates a reference zone of the test strip.
Each LED is optically isolated by light-impermeable baffles 40, which ensure
that each LED
is capable of illuminating only its respective zone of the test strip. However
the surfaces of
the baffles facing LED2 are angled so as to allow both PD1 and PD2 to collect
reflected light
from the maximum area of the reference zone.
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Ii
Figure 5 shows the spatial relationship between the LED and photodiode. The
photodiode is
positioned at a sufficient distance to ensure that it does not receive
specular reflections from
the front cover of the test-strip 30. Specular reflections are a direct
reflection. Thus any light
hitting the test-strip at an angle _ will also reflect at the same angle. Thus
to avoid the PD
detecting specular light, it is offset. The degree of offset is dependent upon
the height D2,
the window opening width Dl.
The substrate 70 supporting the window is made from black plastic and is
chosen to be at a
particular angle _. If the plastic were constructed so as to have a horizontal
roof (as denoted
dashed line 60), light from the LED could bounce of the roof and onto the PD.
To avoid this
the substrate is angled such that light hitting the angled part reflects
directly back (as denoted
by dashed line 62). Again this angle is dependent upon D1 and is approx 40% in
the device
shown by reference to the solid line 64.
Finally the height of the divide is chosen to be a certain height such that
light from the LED
does not shine directly to the PD. The height of the divide will be
determinant upon the
height of the LED. In one exemplary embodiment, the LED height is 1.5mm and
the divide
height 2mm.
In a preferred embodiment the test strip comprises of a layer of a porous
carrier such as
nitrocellulose sandwiched between two layers of plastic such as MYLARO. The
layer
proximal to the light source must be permeable to light, preferably
transparent. In the
situation wherein the PD's and LED are situated on the same side of the test-
strip the layer
distal to the light source must be capable of reflecting light. It is
preferable for this distal
layer to be white to increase contrast and hence the signal to noise ratio.
It is apparent that, in view of the inverse square law, it would generally be
preferred to
position the photodiodes as close as possible to the test strip (i.e. decrease
x), so as to
increase the signal intensity I. However, merely decreasing the vertical
separation y between
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the photodiode and the test strip would increase angle _, decreasing the value
of cos _ and
therefore tend to reduce the signal intensity.
An alternative approach to improve signal intensity would be to re-position
the photodiode
nearer the center of the system, which would simultaneously decrease the
reflection distance
and the angle of reflection. However the distance must be minimized to ensure
that the
maximum intensity of light is detected (the intensity decreases as a function
of the distance
of the PD from the test-strip and the angle of reflection).
Example 3
In one exemplary embodiment, the active area of the photodetector is 2mm x
2mm. The
light source provides light, at least some of which has a wavelength of 635nm.
The height of
the test-strip above the light source is 5.5mm. The wall height separating the
LED's is
2.7mm and the angle of the wall is 30 degrees. The plastic used is black
nylon.
Example 4
Figures 6-11 illustrate an exemplary embodiment of portions of an assay
reader.
Figure 6 shows an exploded view of a baffle arrangement 100 and a printed
circuit board
(PCB) 102 that may receive the baffle arrangement. The baffle arrangement
defines three
windows 104 and includes a location feature 110 which may define an aperture
111 or some
other feature that can engage a corresponding feature 112 on the PCB. The
location feature
110 may also be so sized and shaped as to engage a mating feature on a test
strip (not shown)
when the test strip is introduced to the baffle arrangement. The strip may
thus be locked into
position during an assay measurement. The baffle arrangement also includes
parallel raised
side walls 114 that may guide the test strip into the correct location and
ensure that it both
engages with the location feature and is correctly linearly aligned with the
windows 104 and
not skewed. The PCB includes, among other item not shown, light sources such
as light
emitting diodes (LED's) 106 and light detectors such as photodiodes (PD's)
108. The
LED's and PD's may be mounted in the same plane and positioned under the
respective
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windows 104 such that light emitted from one or more LED's is able to pass
through the
window spaces onto the test-strip and be reflected back down onto one or more
of the PD's.
Figure 7 shows a top plan view of an exemplary embodiment of a baffle
arrangement 110 in
which the light source centers 106a are aligned under their respective windows
104.
Figure 8 provides an underside view of baffle arrangement 100. The arrangement
may
include a number of mounting pins 118 to provide contact points with the PCB
(not shown).
Defining windows 104 are baffles 116 and side barriers 117 that have angled
walls to screen
light as described above.
Figure 9 shows a bottom plan view of the baffle arrangement 100. The light
source centers
106a are aligned under windows 104, and light detector centers 108a are offset
to provide the
appropriate incident angle, as described above.
Figure 10 depicts a longitudinal cross-section (taken at line 10-10 in Figure
7) of baffle
arrangement 100 seated on PCB 102 and a test strip 120 raised from its normal
position in
the baffle arrangement. The light sources 106 are positioned in their
respective windows
104.
Figure 11 is a transverse cross section (taken at line 11-11 in Figure 10)
showing the test
strip 120 in position relative to the baffle arrangement 100. The strip
includes a porous
carrier membrane 122 in which the assay reaction is conducted. Light emanative
from a
light source 106 impinges on the membrane. Light emanating from the membrane
is
detected by the light detector 108. A divider 124 prevents light from source
106 from
shining directly on detector 108.
Example 5
An assay result reader according to the present disclosure may also include a
system for
declaring the result of an assay before completion of the assay, if a analyte
measurement
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signal is above an upper threshold or below a lower threshold. Such systems
are described in
U.S. Patent No. 7,239,394.
Example 6
An assay result reader according to the present disclosure may also include a
system for
detecting flow rate of a fluid sample, such as one described in U.S. Patent
No. 7,317,532.
Example 7
An assay result reader according to the Present disclosure may further include
both an early
declaration system described in U.S. Patent No. 7,239,394 and a flow rate
detection system
described in U.S. Patent No. 7,317,532.
