GB2602268A

GB2602268A - Time-resolved fluorescence reader and method

Info

Publication number: GB2602268A
Application number: GB2020123.2A
Authority: GB
Inventors: Adsul Neeraj
Original assignee: Forsite Diagnostics Ltd
Current assignee: Forsite Diagnostics Ltd
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2022-06-29
Anticipated expiration: 2040-12-18
Also published as: GB202020123D0; GB2602268B

Abstract

An apparatus 100 for making colorimetric and time-resolved fluorescence measurements of an assay 101 comprises: an energy source 102 for illuminating a test/control regions of the assay; a detector 103 comprising a plurality of photodetectors 106 for detecting energy 104 reflected from and/or fluoresced by one or more analyte-bound labels of the assay; and a processor 105. The processor is configured to initiate a time-resolved fluorescence measurement comprising triggering an energy source pulse at one or more first wavelengths corresponding to a fluorescence excitation wavelength of the analyte-bound label, and time-gating the detector to detect fluoresced energy, and subsequently initiate a colorimetric measurement comprising triggering the energy source to illuminate the region of the assay at one or more second wavelengths and triggering the detector to detect said reflected energy. A lateral flow assay comprising both colorimetric and fluorescence labels is claimed.

Description

TIME-RESOLVED FLUORESCENCE READER AND METHOD

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for making colourimetric and time-resolved fluorescence measurements of an assay, and to a lateral flow assay for use with such an apparatus.

BACKGROUND

Lateral flow assays (LFA) are diagnostics tests where a liquid sample is applied to a small nitrocellulose membrane pre-patterned with reagents for detection of particular proteins, cells, chemical molecules or microorganisms. LFAs are used for numerous applications including human diagnostics (e.g. pregnancy, infectious disease, and drug testing), animal health, agricultural, food monitoring and environmental testing. Most existing tests, for example pregnancy tests, are based on the presence or absence of coloured lines on a test strip providing a positive or a negative test result. These types of LFAs are known as colourimetric assays.

For many applications, qualitative colourimetric results are sufficient and in fact the application of LFAs is largely limited to qualitative or semi-quantitative tests. Example colourimetric devices are described in W02015/121672 and WO/2017/203239.

However, other applications of LFAs also exist where the determination of a quantity of analyte in an accurate manner is required. Example of such applications include, in human health, testing of cardiac markers; in animal health, the presence of antibiotics in animals; in agriculture, mycotoxins in food. In such applications, a laboratory-standard, quantitative LEA result in a point-of-contact environment would be advantageous.

Fluorescence-based assays are known to provide higher sensitivity readings than colourimetric-based assays and are typically used when quantitative results are required. Fluorescence-based assays use fluorescent labels which bind to the analyte and which emit photons by fluoresecnce when illuminated by a light source (e.g. UV light). A problem with traditional fluorescence measurement techniques is that they suffer from high levels of background noise. Typically the illuminating light not only causes the label to fluoresce but it also causes scattering. The scattering interferes with the fluorescent signal being measured. In the case of LFAs, scattering from the membrane of the lateral flow test strip can be particularly severe.

In order to reduce background noise, additional optical components such as lenses and filters might be placed in the optical path between the test strip and light detector. Additional components may increase the overall cost and complexity of the device.

An alternative and/or additional way to reduce noise of fluorescence measurements is to use a time-resolved fluorescence measurement technique. Time-resolved fluorescence techniques separate fluorescence of interest from background noise through lifetime differences. A fluorescent label with a long fluorescence lifetime is excited with a short pulse of light and, after waiting a period of time for the background and unwanted fluorescence to decay to a low level, the remaining long-lived fluorescence signal is measured. The long-lived fluorescence signal arises from the fluorescent label bound to the analyte so the signal's intensity gives a quantitative indication of the amount of analyte present.

An example of a time-resolved fluorescence measurement based assay reader is described in Time-resolved luminescent lateral flow assay technology, Xuedong Song, Michael Knotts, Analytica Chimica Acta 626 (2008), 186-192. This uses a transmission mode measurement where the light source and detectors are on opposite sides of an opaque backing which are transparent only to the fluorescent emission. This technique reduces scattering and other noise but makes the reader unsuitable for colourimetric-based reading because the light reflecting from one or more lines on the assay does not reach the detectors on the opposing side of the backing. It also requires multiple sets of sensors to be able to detect not only the measurement signal but also a reference signal of the light sources, thereby increasing complexity of the device.

Typically, devices that are able to make both colourimetric and fluorescence measurements do so by using separate optical paths and optical components for each type of measurement. Each path thus has its own separate optical components such as filters, lenses, diffraction gratings, collimators, prisms and others, as well as separate sets of detectors and/or illumination sources. This is because the illumination and measurement requirements of the two techniques are different. To switch between measurement types, the optical path needs to be switched and this is typically achieved by using a motor and/or other moving parts which may break down. This may further increase the cost and complexity of such devices.

An improved apparatus and method for reading an assay is required.

STATEMENT OF INVENTION

In general terms, the disclosure is directed to an apparatus for reading an assay, for example a lateral flow assay, with both time-resolved fluorescence detection (TRFL) and colourimetric detection capability, including quantitative measurements of the assay, in a compact, desktop form. The apparatus achieves compactness by combining TRFL and colourimetric techniques in a single, multiplexed optical path. The use of a single optical path for both types of measurements results in fewer optical components so the apparatus is not only more compact but also less complex and is thus cheaper to produce and easier to calibrate and maintain.

A problem of multiplexing colourimetric and fluorescence measurement signals in a single optical path is that the detector hardware requirements of fluorescence measurements are very different to those of colourimetric measurements.

In particular, the accuracy of fluorescence measurement signals depends on how soon after the stopping of fluorescent label excitation the fluorescence data can be captured.

If there is a time delay, the initial fluorescence from the labels will be missed and the total estimated analyte may thus be underestimated. In traditional TRFL readers, this problem is overcome by achieving rapid data acquisition using a photomultiplier tube or ultrafast camera on each test line of an assay; these types of sensors require lenses, filters and other optical components, and are bulky, expensive and therefore not suitable for a cheap, compact reader device, especially when an assay has multiple test lines.

Whilst Time-resolved luminescent lateral flow assay technology, Xuedong Song, Michael Knotts, Analytica Chimica Acta 626 (2008), 186-192 attempts to overcome this problem by replacing each photomultiplier tube or ultrafast camera with a cheaper and more compact time-gated photodiode, this significantly increases the error in the obtained quantitative measurement results in a point-of-care environment. This is because the user must manually align the test lines of the assay with the smaller, more compact photodiode positions. Any misalignment introduces large errors in what is intended to be a highly sensitive quantitative measurement.

The apparatus of the present disclosure solves these and other problems by using a detector comprising a plurality of photodetectors, such as photodiodes, for each test line of the assay. In this way, the resolution of the detector is greater than one pixel per test line. Accordingly, consistent alignment of each test line with the position of each photodetector is not required as any misalignment with one photodetector is compensated for by a stronger signal at an adjacent photodetector.

Further, whilst photodetectors such as photodiodes may not be as fast as photomultiplier tubes or ultrafast cameras of traditional TRFL techniques, they are significantly more compact and cheaper. They are also significantly cheaper and more compact than other imaging tools such as CCD cameras. To overcome the slower speeds of photodiodes, use of a time-gated signal synchronised to the end of a fluorescence excitation pulse from the energy source can significantly improve the speed and accuracy of measurements made by photodiodes, making them suitable for use with TRFL measurements.

As photodetectors such as photodiodes may be sensitive to a wide range of wavelengths they can be used for both the colourimetric measurements (e.g. when a test line of the assay is illuminated with visible light such as red, green, blue, and/or white light) as well as for the TRFL measurements (e.g. when the test line is illuminated by fluorescence inducing UV light) all in a single optical path. As a result, the apparatus of the present disclosure permits the multiplexing of a colourimetric measurement optical path and a TRFL optical path and requires fewer optical components, requires no moving parts, is more compact, and is cheaper to produce than readers such as those that use photomulfiplier tubes or ultrafast cameras described above. The apparatus is also more accurate and reliable in a point-of-care environment than the reader of Time-resolved luminescent lateral flow assay technology, Xuedong Song, Michael Knotts, Analytica Chimica Acta 626 (2008), 186-192.

As described above, TRFL measurement techniques separate fluorescence excitation and signal acquisition in time thus resulting in measurements with a much higher signal-to-noise ratio, enabling interpretation of high sensitivity assays with limit-ofdetection (LoD) at least 3 orders of magnitude better than a colourimetric approach, including reaching micromolar and femtomolar sensitivity. TRFL measurements allow lateral flow technology to be used in assays and diagnostic tests previously not capable of being tested with colourimetric methods, and in a manner that delivers laboratory standard test results in point-of-care environments including, for example, GP surgeries, veterinary clinics, and farms. Non-limiting example uses of the invention include high sensitivity C-reactive protein (CRP) tests to determine cardiovascular risk, ultra-sensitive troponin tests for myocardial infraction, and rapid detection of low levels of mycotoxins and plant pathogens including xylella fastidiosa.

According to a first aspect, there is provided an apparatus for making colourimetric and time-resolved fluorescence measurements of an assay, the apparatus comprises: an energy source for illuminating a test and/or control region of the assay; a detector for detecting energy reflected from and/or fluoresced by one or more analyte-bound labels of the assay; and a processor configured to: initiate a time-resolved fluorescence measurement comprising: (i) triggering the energy source to start illuminating the test and/or control region of the assay at one or more first wavelengths at a first time and to stop said illuminating at a second time, the one or more first wavelengths corresponding to a fluorescence excitation wavelength of the analyte-bound label, and (ii) sending a signal to the detector to time-gate said detecting of said fluoresced energy at or after the second time, and initiate a colourimetric measurement comprising: at a third time, triggering the energy source to illuminate the region of the assay at one or more second wavelengths and triggering the detector to detect said reflected energy, wherein the detector comprises a plurality of photodetectors per test and/or control region of the assay.

Optionally, the photodetectors comprise photodiodes.

Optionally, the photodetectors are arranged in a line.

Optionally, when in use, the energy source is positioned to illuminate a first surface of the assay from a first direction and the detector is positioned to detect said reflected and/or fluoresced energy from said first direction.

Optionally, the energy source comprises a plurality of light emitting diodes, each configured to emit energy at the one or more first wavelengths and/or the one or more second wavelengths.

Optionally,n the one or more first wavelengths are between 360-400nm and the one or more second wavelengths are between 400-700nm.

Optionally, the analyte-bound label is a Europium based fluorescent label.

Optionally, the apparatus comprises an analogue-to-digital converter configured to convert an analogue output of the detector to a digital signal and to send the digital signal to the processor.

According to a second aspect, there is provided a lateral flow assay for use with the apparatus above, the lateral flow assay comprising: a sample pad; a conjugate pad; a nitrocellulose membrane comprising a test region and a control region; and a wicking pad, wherein the test region comprises colourimetric labels and fluorescence labels configured to bind to one or more analytes in a sample introduced to the sample pad.

According to a third aspect, there is provided a kit of parts comprising: the apparatus above; and the lateral flow assay above.

According to a fourth aspect, there is provided a method for making colourimetric and time-resolved fluorescence measurements of an assay, the method comprises: illuminating, with an energy source, a test and/or control region of the assay; detecting, with a detector, energy reflected from and/or fluoresced by one or more analyte-bound labels of the assay; initiating a time-resolved fluorescence measurement comprising: (i) triggering the energy source to start illuminating the test and/or control region of the assay at one or more first wavelengths at a first time and to stop said illuminating at a second time, the one or more first wavelengths corresponding to a fluorescence excitation wavelength of the analyte-bound label, and (ii) sending a signal to the detector to time-gate said detecting of said fluoresced energy at or after the second time, and initiating a colourimetric measurement comprising: at a third time, triggering the energy source to illuminate the region of the assay at one or more second wavelengths and triggering the detector to detect said reflected energy, wherein the detector comprises a plurality of photodetectors per test and/or control region of the assay.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an apparatus in accordance with the present disclosure.

Figure 2 shows an illustrative circuit diagram according to the present disclosure.

Figure 3 shows a plot of signal intensity in arbitrary units versus pixel position of data captured during a colourimetric measurement according to the present disclosure.

Figure 4 shows a plot of signal intensity in arbitrary units versus pixel position of data captured during a TRFL measurement according to the present disclosure

DETAILED DESCRIPTION

Generally speaking, the disclosure provides an apparatus and method for making colourimetric and time-resolved fluorescence measurements of an assay, for example a lateral flow assay, a lateral flow assay for use with such an apparatus, and a kit of parts. The apparatus overcomes the above-described problems by providing a plurality of photodetectors for each test line of the assay. This means the assay need not be perfectly aligned inside the apparatus, ensuring reproducibility and reliability of quantitative measurements in a point-of-care environment where a user may not be able to consistently and accurately position the assay in the apparatus.

Some examples are given in the accompanying figures.

Figure 1 shows an apparatus 100 according to the present disclosure for making colourimetric and time-resolved fluorescence measurements of an assay 101. The apparatus 100 comprises an energy source 102 for illuminating one or more regions of the assay, for example test and/or control regions, typically lines, a detector 103 for detecting energy 104 reflected from and/or fluoresced by one or more analyte-bound labels of the assay 101, and a processor 105. The processor 105 is configured to initiate both a time-resolved fluorescence (TRFL) measurement of the assay 101 and a colourimetric measurement of the assay 101. The detector 103 comprises a plurality of photodetectors 106 for each test line of the assay 101. As described above, this enables the resolution of the detector 103 to be greater than one pixel per test line. Accordingly, consistent alignment of each test line with the position of each photodetector 106 is not required as any misalignment with one photodetector 106 is compensated for by a stronger signal at an adjacent photodetector 106 and thus provides a complete signal profile across the region of the assay 101 on which the test and/or control lines are present. The apparatus 100 may comprise a housing (not shown) having internal structuring to provide an enclosed space into which the assay 101 may be inserted, for example, into a slot of the housing.

The TRFL measurement comprises triggering the energy source 102 to start illuminating the region of the assay 101 at one or more first wavelengths at a first time and to stop said illuminating at a second time, thus providing a pulse of light incident onto the surface of the assay 101 facing the energy source 102. The one or more first wavelengths correspond to a fluorescence wavelength of the analyte-bound label. The pulse excites any analyte-bound fluorescent labels present on the illuminated region of the assay 101. When the pulse ends, the excited labels emit energy in the form of fluorescence for a period of time, depending on the fluorescence lifetime of the label used. The fluoresced energy is then detected by the detector to provide a quantitative estimate of the amount of fluorescent label present that correlates with the amount of analyte present thus allowing a quantitative estimate of the amount of analyte present to be made.

As described above, TRFL measurement techniques such as those described above separate fluorescence excitation and signal acquisition in time thus resulting in measurements with a much higher signal-to-noise ratio, enabling interpretation of high sensitivity assays with limit-of-detection (LoD) typically at least three orders of magnitude better than a colourimetric approach, including reaching micromolar, nanomolar and femtomolar sensitivity. TRFL measurements allow lateral flow technology to be used in assays and diagnostic tests previously not capable of being tested with colourimetric methods, and in a manner that delivers laboratory standard test results in point-of-care environments including, for example, general practice (GP) surgeries, veterinary clinics, and farms. Non-limiting example uses of such TRFL measurements include high sensitivity C-reactive protein (CRP) tests to determine cardiovascular risk, ultra-sensitive troponin tests for myocardial infraction, and rapid detection of low levels of mycotoxins and plant pathogens including xylella fastidiosa.

As the fluorescence life-time can be very short, particularly when the amount of analyte present is low, detection speed, accuracy and signal strength can be increased by using time-gated detection synchronised to the end the excitation pulse from the energy source 102. Accordingly, the processor 105 is also configured to send a signal to the detector 103 to time-gate the detecting of the fluoresced energy at or shortly after the end of the excitation pulse. For example at the end of the pulse or around 0.2- 0.4 nanoseconds thereafter.

In contrast, the colourimetric measurement comprises, at a third time, triggering the energy source 102 to illuminate the region of the assay 101 at one or more second wavelengths, for example wavelengths corresponding to one or more of red, green, blue and/or white light, and triggering the detector 103 to detect the reflected energy 104. Unlike the fluoresced energy which has a limited life-time, the reflected energy may be detected as long as the energy source is on so no time-gating or synchronisation with an illumination pulse is required.

As described above, the detector 103 comprises a plurality of photodetectors for each test line of the assay 101. The photodetectors may comprise photodiodes and may be arranged in a line so as to be aligned with a longitudinal direction of the strip of a lateral flow assay. As long as at least the test and/or control lines of the assay are positioned below at least some of the photodetectors, perfect alignment of the assay in the apparatus is not required.

It is envisaged that, when in use, the energy source 102 is positioned the same side of the assay as where both the reflected and/or fluoresced energy 104 is measured. In other words, the energy source 102 may be positioned to illuminate a first surface of the assay 101 (namely the surface on which the test and/or control lines are present) from a first direction and the detector 103 may be positioned to detect said reflected and/or fluoresced energy from the first direction. When a detector is positioned on the opposite side of the assay to the energy source, additional reference or calibration detectors on the side of the energy source are necessary and only assays can be used that are transparent to the chosen fluorescence wavelength. The arrangement of the present disclosure is thus advantageous because placing the detector 103 on the same side as the energy source 102 reduces the number of sensors required (i.e. no reference detectors are required) and a wider variety of assays can be used with the apparatus because there is no requirement for transparency to the fluorescence wavelength. The arrangement thus provides a cheaper, more compact device that can read a wider variety of assay types. By providing a compact device in this way, its calibration may be performed quickly and efficiently in a factory setting during manufacture before being shipped to a point-of-care environment without further need for calibration.

The energy source 102 may comprise a plurality of light emitting diodes (LEDs) each configured to emit energy at the one or more first wavelengths and/or one or more second wavelengths depending on which of the two measurement types is being made. It is envisaged that the one or more first wavelengths for the TRFL measurement are between 360-400nm and the one or more second wavelengths for the colourimetric measurement are between 400-700nm. Other wavelengths may also be used depending on, for example, the fluorescence excitation wavelength of the fluorescent labels used on the assay. The photodetectors 106 of the detector 103 are accordingly configured to be sensitive to both the wavelength of the reflected and/or fluoresced energy 104 and accordingly there is no need to provide separate detectors or optical pathways for colourimetric and TRFL measurements.

The analyte-bound label may comprise a Europium based fluorescent label, for example a lanthanide chelate label such as Europium ion (Eu3+) having a long fluorescence lifetime of around microseconds to milliseconds, which may be excited by energy having a wavelength of between 320-380nm, preferably between 340-365nm, for example at 365nm. Europium based labels typically emit fluoresced energy at around 610nm. The photodetectors 106 of the detector 103 may thus be configured to be sensitive to wavelengths between 400-700nm and are thus suitable for making both the TRFL and the colourimetric measurements.

Figure 2 shows an illustrative circuit diagram according to the present disclosure. As described above, the apparatus 100 comprises a processor 106 configured to initiate the TFL measurement and the colourimetric measurement. The processor 106 is configured to send and receive signals to and from the energy source 102 and the detector 103. Optionally, when the detector 103 output is an analogue signal, for example in the case of a plurality of photodiodes, the apparatus 100 may comprise an analogue-to-digital converter that may be used to convert the signal to a digital signal suitable for the processor 106.

The apparatus 100 may also comprise one or more of the following additional components not shown in Figure 2 which may be in direct or indirect communication with the processor 106, and which may be provided on one or more printed circuit boards with the processor 106.

A programmable current driver to drive the energy source 102 for colourimetric measurements and a pulse driver with a trigger and time sync module to drive the energy source 102 for TRFL measurements.

A micro-switch and/or Schmitt trigger for detecting the presence of an assay in the apparatus when it is inserted and for communicating a signal to the processor 106 to indicate the presence of the assay.

A temperature sensor for determining the running temperature of the processor, the temperature energy source 102 and/or detector 103, and/or the temperature of the ambient environment in which the assay is positioned in the apparatus.

A clock on which the energy pulse and the time-gate signal of the TRFL measurement may be based. The clock may comprise, for example, a low drift crystal oscillator.

One or more interfaces and/or ports suitable for interfacing with external connections, for example a USB 2.0 connection and/or a network connection. These may be used, for example, to transfer any collected measurement data and associated information from the apparatus 100 to a storage device.

A power supply and associated power regulator may be provided, for example through the USB connection, to power the apparatus and provide a reference voltage for use by the processor 106 and/or other components of the apparatus.

Figure 3 shows a plot 300 of signal intensity in arbitrary units versus pixel position of data captured during a colourimetric measurement according to the present disclosure. As described above, a plurality of photodetectors are present per test and/or control region of the assay and each pixel position corresponds to one photo detector. In the example of Figure 3 there are 256 pixels corresponding to 256 individual photodetectors such as photodiodes. The different curves shown in Figure 3 respectively represent measurements of test strips with different lines or other features under various lighting conditions and together show that an apparatus according to the present disclosure may accurately estimate signal intensity and thus test and/or control region position and other colourimetric information of an assay. The curves shown in Figure 3 represent data captured under the following conditions: red LED and green LED illuminating a red printed line on a test strip 301, red LED and green LED illuminating a blue printed line on a test strip 302, red Led illuminating a blue printed line on a test strip 303 (the data points overlapping with the other blue printed test strip 302), green LED illuminating a red printed line on a test strip 304, green LED illuminating a blue printed line on a test strip 305, green LED illuminating a blank test strip 306, green LED illuminating a 3 line sera-buffer test strip 307.

Figure 4 shows a plot 400 of signal intensity in arbitrary units versus pixel position of data captured during a TRFL measurement according to the present disclosure. As described above, a plurality of photodetectors are present per test and/or control region of the assay and each pixel position corresponds to one photo detector. In the example of Figure 4 there are 256 pixels corresponding to 256 individual photodetectors such as photodiodes. The different curves shown in Figure 4 respectively represent measurements of test strips with different lines or other features having different concentrations of fluorescent marker and together show that an apparatus according to the present disclosure may accurately estimate signal intensity and thus test and/or control region position and other TRFL measurement information of an assay. The curves shown in Figure 4 represent data captured under the following TRFL conditions: UV LED illuminating a test strip with test regions having a fluorescent marker concentration of 1 part in 5 (401), UV LED illuminating a test strip with test regions having a fluorescent marker concentration of 1 part in 10 (402), UV LED illuminating a test strip with test regions having a fluorescent marker concentration of 1 part in 100 (403), and UV LED illuminating a test strip with negligible presence of fluorescent marker.

Although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Claims

CLAIMS: 1. An apparatus for making colourimetric and time-resolved fluorescence measurements of an assay, the apparatus comprising: an energy source for illuminating a test and/or control region of the assay; a detector for detecting energy reflected from and/or fluoresced by one or more analyte-bound labels of the assay; and a processor configured to: initiate a time-resolved fluorescence measurement comprising: (i) triggering the energy source to start illuminating the test and/or control region of the assay at one or more first wavelengths at a first time and to stop said illuminating at a second time, the one or more first wavelengths corresponding to a fluorescence excitation wavelength of the analyte-bound label, and OD sending a signal to the detector to time-gate said detecting of said fluoresced energy at or after the second time, and initiate a colourimetric measurement comprising: at a third time, triggering the energy source to illuminate the region of the assay at one or more second wavelengths and triggering the detector to detect said reflected energy, wherein the detector comprises a plurality of photodetectors per test and/or control region of the assay.
2. The apparatus of any preceding claim, wherein the photodetectors comprise photodiodes.
3. The apparatus of any preceding claim, wherein the photodetectors are arranged in a line.
4. The apparatus of any preceding claim, wherein, when in use, the energy source is positioned to illuminate a first surface of the assay from a first direction and the detector is positioned to detect said reflected and/or fluoresced energy from said first direction.
5. The apparatus of any preceding claim, wherein the energy source comprises a plurality of light emitting diodes, each configured to emit energy at the one or more first wavelengths and/or the one or more second wavelengths.
6. The apparatus of any preceding claim, wherein the one or more first wavelengths are between 360-400nm and the one or more second wavelengths are between 400-700nm.
7. The apparatus of any preceding claim, wherein the analyte-bound label is a Europium based fluorescent label.
8. The apparatus of any preceding claim, comprising: an analogue-to-digital converter configured to convert an analogue output of the detector to a digital signal and to send the digital signal to the processor.
9. A lateral flow assay for use with the apparatus of any one of claims 1-8, the lateral flow assay comprising: a sample pad; a conjugate pad; a nitrocellulose membrane comprising a test region and a control region; and a wicking pad, wherein the test region comprises colourimetric labels and fluorescence labels configured to bind to one or more analytes in a sample introduced to the sample pad.
10. A kit of parts comprising: the apparatus of any one of claims 1-8; and the lateral flow assay of claim 9.
11. A method for making colourimetric and time-resolved fluorescence measurements of an assay, the method comprising: illuminating, with an energy source, a test and/or control region of the assay; detecting, with a detector, energy reflected from and/or fluoresced by one or more analyte-bound labels of the assay; initiating a time-resolved fluorescence measurement comprising: (i) triggering the energy source to start illuminating the test and/or control region of the assay at one or more first wavelengths at a first time and to stop said illuminating at a second time, the one or more first wavelengths corresponding to a fluorescence excitation wavelength of the analyte-bound label, and (ii) sending a signal to the detector to time-gate said detecting of said fluoresced energy at or after the second time, and initiating a colourimetric measurement comprising: at a third time, triggering the energy source to illuminate the region of the assay at one or more second wavelengths and triggering the detector to detect said reflected energy, wherein the detector comprises a plurality of photodetectors per test and/or control region of the assay.