Reading devices and assay devices for use therewith

Details Reading devices and assay devices for use therewith Reading devices and assay devices for use therewith

1998-05-14

2001-05-22

McKane, Elizabeth (Department: 1744)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Calorimeter

C422S082050, C422S082090

Reexamination Certificate

active

06235241

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to devices for reading the results of assays, to assay devices for use in conjunction with reading devices, and to methods using such devices.
An objective of the invention is to provide assay result reading devices and associated sample testing devices which can provide accurate quantitative assay information in a simple, quick and cost effective manner. Such devices can be used in a wide range of situations such as hospitals, clinics, doctors' offices, and the home. Depending on the circumstances, the analyte under investigation can also vary widely. Examples are infectious disease organisms or markers, metabolites in body fluids indicative of a change in the health or condition of a patient, and administrable or ingestable substances such as medicaments or drugs of abuse.
The invention is particularly, although not exclusively, concerned with assays which can be performed by comparatively untrained people and especially in the home.
BACKGROUND TO THE INVENTION
Home-use assay devices such as pregnancy tests are now well established. In the case of a pregnancy test, which merely needs to provide the user with a “yes
o” result, the technology now available enables the assay result to be read easily by eye without the need for any ancillary equipment.
Home-use assays are intended primarily to detect physiological changes in the human body, with the objective of promoting the health, general well-being or lifestyle of the individual. The consumer is becoming increasingly health conscious, and the ability of the consumer to monitor his or her bodily functions is being encouraged.
In some instances this can facilitate the interaction between the individual consumer and the medical profession (GP).
There are many assays indicative of physiological changes in the human body which currently can only be performed using sophisticated laboratory techniques. In order to provide useful information concerning the individual under test, such assays generally need to yield a result in precise numerical terms, eg. the concentration of a specific analyte in a body fluid.
Accordingly there is a need for an assay system, especially applicable to the testing of body fluid samples in the home, which combines convenience of sample testing together with simple and cost-effective numerical determination of the assay result.
Many assay devices are described in the technical literature with suggestions that the assay result can be read using optical equipment. The use of fluorescence emission, or light reflectance, is often suggested. Such techniques are mostly appropriate for use in sophisticated laboratories. In EP-A2-212599, which describes multizone analytical elements having a detectable signal concentrating zone, the suggestion is made that a detectable signal indicative of an assay result in the zone can be measured by electromagnetic radiation, such as light, transmitted through the zone. EP-A2-212599 indicates that the element can be made from porous fibrous materials, such as paper and nitrocellulose. However, no practical details are provided to indicate how an accurate measurement might be made using transmitted light.
SUMMARY OF THE INVENTION
By the invention, we have found that quantitative information can be derived by transmission reading of an assay strip or the like if the incident electromagnetic radiation is uniform across a region of the test strip which encompasses and extends beyond the test zone.
In one embodiment, the invention provides a method of “reading” the result of an assay effected by concentrating a detectable material in a comparatively small zone of a carrier in the form of a strip, sheet or layer through the thickness of which electromagnetic radiation, such as light, is transmissible, wherein at least a portion of one face of said carrier is exposed to incident electromagnetic radiation which is substantially uniform across the entire portion, said portion including said zone, and electromagnetic radiation emerging from the opposite face of said carrier is measured to determine said assay result.
PREFERRED EMBODIMENTS OF THE INVENTION
Preferably, the incident electromagnetic radiation is of substantially uniform intensity.
This uniformity can be achieved, for example, by providing a columated source of electromagnetic radiation, using conventional focussing means such as lenses and light guides to provide parallel incident electromagnetic radiation which falls essentially normally across the entire exposed portion of the carrier.
However, in a more preferred embodiment of the invention, the incident electromagnetic radiation is diffuse and bathes the exposed portion of the carrier uniformly in a randomly scattered manner.
In another embodiment, the invention provides an assay device comprising a porous liquid-permeable carrier strip or sheet through the thickness of which electromagnetic radiation is transmissible diffusely, said carrier being within a casing, said carrier including at least one detection zone in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in said detection zone, detection of said material being effected as a response to said electromagnetic radiation, and said casing having electromagnetic radiation transmitting regions enabling electromagnetic energy from an external source to be passed through said device, said detection zone lying in the electromagnetic radiation path between said electromagnetic radiation transmitting regions.
Preferably, the porous carrier strip or sheet comprises paper, nitrocellulose or the like, preferably of a thickness not exceeding 1 mm.
In yet another embodiment, the invention provides an assay device and assay result reader combination, wherein:
a) said device comprises a porous liquid-permeable carrier strip or sheet through the thickness of which electromagnetic radiation is transmissible diffusely, said carrier preferably being within a casing or cover, said carrier including at least one detection zone in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in said detection zone;
b) said casing or cover, if present, has electromagnetic radiation transmitting regions enabling electromagnetic radiation from an external source to be passed through said device, said detection zone lying in a path between said transmitting regions;
c) said assay result reader has receiving means for receiving at least a portion of said device, said portion including said detection zone to present said detection zone to reading means, said reading means incorporating a source of uniform electromagnetic radiation and one or more sensors located such that upon insertion of said device into said receiving means, electromagnetic radiation can be passed through said device and the intensity of electromagnetic radiation emerging from said device can be detected by said sensor(s).
Preferably, said receiving means incorporates interlocking means engagable with corresponding interlocking means on said device to ensure that upon receipt of said device by said reader said detection zone(s) is located and maintained in a predetermined spacial relationship relative to said reading means.
Preferably, said receiving means includes actuating means triggered by said receipt of said device, said actuating means causing said reading of said detection zone(s) to be initiated.
If the assay device is provided with a casing, it is advantageous if said device casing includes internal registration means which engages with corresponding registration means associated with said carrier such that said detection zone within said device casing is located in a predetermined spacial relationship relative to said registration means on said device casing. Preferably, said internal registration means comprises a pin or the like, engagable with a hole, indentation of the like in said carrier, said detection zone being at a predetermined location on said

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