Iconic colorimetric test device with reduced susceptibility to false positive and false negative readings
First Claim
1. A test device for analyzing a liquid sample for the presence of a selected analyte, said test device comprising:
- a light-transmitting, liquid-impermeable substrate sheet coated on one side with an analyte indicator lamina and on an opposing side with a pigment lamina, said analyte indicator lamina reactive with said analyte in a reaction producing a color change in said analyte indicator lamina, and said pigment lamina being of the same composition as that of said indicator lamina, so that said pigment lamina is of a color visually indistinguishable from that of said analyte indicator lamina when said analyte indicator lamina is in unreacted condition, said pigment lamina fully covering a selected test region on said substrate, andmeans for restricting said color change in said analyte indicator lamina to a restricted area within, and smaller than, said test region, thereby leaving adjacent areas within said test region unchanged.
3 Assignments
0 Petitions
Accused Products
Abstract
Laminated test devices in which positive results are detected by the appearance of a symbol on the surface of the device due to a color change in an indicator in the device are improved by placing the indicator lamina on one side of a light-transmissive substrate sheet and a pigment lamina on the other side, the indicator lamina forming the icon and the pigment lamina forming the background, the pigment being the color of the indicator prior to the color change. This arrangement reduces false positive readings by obscuring the outlines of the symbol prior to the color change. False negative readings are reduced by further changes in the arrangement of the laminae.
22 Citations
17 Claims
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1. A test device for analyzing a liquid sample for the presence of a selected analyte, said test device comprising:
- a light-transmitting, liquid-impermeable substrate sheet coated on one side with an analyte indicator lamina and on an opposing side with a pigment lamina, said analyte indicator lamina reactive with said analyte in a reaction producing a color change in said analyte indicator lamina, and said pigment lamina being of the same composition as that of said indicator lamina, so that said pigment lamina is of a color visually indistinguishable from that of said analyte indicator lamina when said analyte indicator lamina is in unreacted condition, said pigment lamina fully covering a selected test region on said substrate, and
means for restricting said color change in said analyte indicator lamina to a restricted area within, and smaller than, said test region, thereby leaving adjacent areas within said test region unchanged. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- a light-transmitting, liquid-impermeable substrate sheet coated on one side with an analyte indicator lamina and on an opposing side with a pigment lamina, said analyte indicator lamina reactive with said analyte in a reaction producing a color change in said analyte indicator lamina, and said pigment lamina being of the same composition as that of said indicator lamina, so that said pigment lamina is of a color visually indistinguishable from that of said analyte indicator lamina when said analyte indicator lamina is in unreacted condition, said pigment lamina fully covering a selected test region on said substrate, and
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14. A test device for analyzing a liquid sample for the presence of a selected analyte, said test device comprising:
- a light-transmitting, liquid-impermeable substrate sheet coated on one side with an analyte indicator lamina and on an opposing side with a pigment lamina, said analyte indicator lamina reactive with said analyte in a reaction producing a color change in said analyte indicator lamina, and said pigment lamina being of the same composition as that of said indicator lamina, so that said pigment lamina is of a color visually indistinguishable from that of said analyte indicator lamina when said analyte indicator lamina is in unreacted condition, said pigment lamina fully covering a selected test region on said substrate, and means for restricting said color change in said analyte indicator lamina to a restricted area within, and smaller than, said test region, thereby leaving adjacent areas within said test region unchanged;
and further comprising a control indicator lamina that is reactive with said sample in a reaction producing a color change in said control indicator lamina regardless of whether said analyte is present in said sample. - View Dependent Claims (15, 16, 17)
- a light-transmitting, liquid-impermeable substrate sheet coated on one side with an analyte indicator lamina and on an opposing side with a pigment lamina, said analyte indicator lamina reactive with said analyte in a reaction producing a color change in said analyte indicator lamina, and said pigment lamina being of the same composition as that of said indicator lamina, so that said pigment lamina is of a color visually indistinguishable from that of said analyte indicator lamina when said analyte indicator lamina is in unreacted condition, said pigment lamina fully covering a selected test region on said substrate, and means for restricting said color change in said analyte indicator lamina to a restricted area within, and smaller than, said test region, thereby leaving adjacent areas within said test region unchanged;
Specification