Chemistry: analytical and immunological testing – Optical result – With reagent in absorbent or bibulous substrate
Reexamination Certificate
2001-05-14
2003-11-04
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
With reagent in absorbent or bibulous substrate
C436S164000, C422S051000, C422S067000
Reexamination Certificate
active
06642058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an analysis method for determining physical density or activity of a specific biochemical component contained in a liquid sample (e.g., blood or urine) dripped on a dry chemical analysis element having a reagent layer by measuring change in optical density of a reacted portion on the dry chemical analysis element where color reaction has occurred, wherein the color reaction is chemical reaction, biochemical reaction or immunoreaction between the reagent layer and the specific biochemical component.
2. Description of the Related Art
Recently, there has been put into practice a dry chemical analysis element of an integrated multi-layered type, which is used to determine physical density or activity of a specific chemical component contained in a liquid sample dripped thereon, or to determine physical density of solid component contained in the liquid sample dripped thereon. Further, analysis elements of similar functions, e.g., filter-paper type elements and applications thereof (including both single layer types and multi-layered types) have also been developed and partly put into practice.
When quantitatively analyzing the chemical components or the like contained in the liquid sample using a dry chemical analysis element, the liquid sample is dripped onto the chemical analysis element (onto a spreading layer when the element is provided with the spreading layer or directly onto the reagent layer when the element is not provided with the spreading layer). The dry chemical analysis element is thereafter held at a constant temperature for a predetermined time in an incubator, so that coloring reaction (pigment-generating reaction or color-changing reaction of the reagent) is promoted on the dry chemical analysis element. After the coloring reaction, change in the optical density of the reacted portion is optically measured. That is, measurement light including a wavelength, which is pre-selected according to the combination of the target chemical component and the reagent contained in the reagent layer, is projected onto the dry chemical analysis element to measure the change in the optical density of the reacted portion on the reagent layer. Then the physical density or the activity of the chemical component is determined based on of the measured optical density referring to a predetermined calibration curve depicting the relationship between the physical density or the activity of the chemical component and the change in the optical density.
The dry chemical analysis element of the integrated multi-layered type generally comprises a substrate of an organic polymer and at least one reagent layer formed on the substrate. Preferably, the dry chemical analysis component additionally comprises a spreading layer superposed on the reagent layer. The dry chemical analysis element of the integrated multi-layered type is generally in the form of a film chip of a predetermined shape such as a square or a rectangle. The film chip may be provided with a frame of an organic polymer for facilitating automated handling of the dry chemical analysis element. Also, there has been proposed an analysis technique of using the film chip by itself without use of the frame.
The optical density of the reacted portion can be measured by extracting light of a certain wavelength from the measurement light emitted by a light source using an interference filter or the like, guiding the light of a certain wavelength through optical fibers or the like, focusing the guided light onto a spot on the dry chemical analysis element using a lens, and measuring reflected light from the spot using a photo-detector mounted in a photometric head. Examples of such a technique for measuring the optical density are disclosed in, for example, Japanese Patent Publication No. 5(1993)-72976 and Japanese Unexamined Patent Publication No. 7(1995)-120477.
However, there has been a problem with the above technique for measuring the optical density that accuracy of measurement may be degraded because of non-uniformity in the amount of the liquid sample dripped on the element or because of difference between an accurate sample-dripped position and a measured position. For this reason, a relatively large amount of the liquid sample has been required to maintain the accuracy of measurement at a reasonable level.
In addition, when the measurement light is focused onto an area having no liquid sample spread thereon or onto a boundary area where only an insufficient amount of the liquid sample has been spread, a large error may be included in the measured optical density because strong reflection may occur on such an area despite little or no liquid sample being spread thereon. Thus, it is preferable to focus the measurement light not onto such an area, but onto an area where a sufficient amount of the liquid sample has been spread.
In this respect, the dry chemical analysis element is usually provided with the spreading layer superposed on the reagent layer, so that the liquid sample dripped substantially onto the center of the element may spread isotropically to provide an area capable of effective color reaction which is sufficiently larger than the beam spot of the measurement light. The measurement light is required to have a beam spot of 4-6 mm in diameter so that a sufficiently large amount of the reflected light is obtained to maintain the accuracy of measurement at a reasonable level. The amount of the liquid sample required to spread beyond such a beam spot is about 10 &mgr;l. Even if the required amount of the liquid sample is dripped on the spreading layer, about 50% of the liquid sample may constitute a non-uniform component which makes the reflection amount due to the color reaction non-uniform, instead of spreading uniformly over the entire spreading layer. Influence of such spreading characteristics upon the measuring accuracy may be reduced by accurately regulating the dripping amount of the liquid sample. However, the dripping amount of the liquid sample must be regulated by controlling injection and aspiration of the liquid sample with high accuracy, which is extremely difficult in practice.
In practical implementation, there may be a slight difference between the accurate sample-dripped position (i.e., the position where the most active color reaction occurs) and the measured position. When the difference becomes large, a large error may be included in the measured optical density because the measured optical density may reflect the state at the position with an insufficient amount of the liquid sample where only a low degree of the color reaction has occurred. To avoid such an error, the liquid sample is required to be spread over a relatively large area so that the measured position falls within the covered area. In this respect, a relatively large amount of the liquid sample must be collected, which is burdensome for a weak patient (e.g., a patient in a serious state, an old patient or a child) and which may be impossible for a subject such as a small animal.
Describing in detail referring to figures, shown in
FIG. 7A
is a sectional view of a dry chemical analysis element
1
in a slide-like form including a film chip
2
held by a frame
3
. The frame
3
has a circular aperture at the center thereof. The film chip
2
includes a substrate, at least one reagent layer formed on the substrate, and a spreading layer superposed on the reagent layer.
FIG. 7B
is a plane view of the dry chemical analysis element
1
of
FIG. 7A
, provided with a sufficient amount of the liquid sample dripped thereon.
FIG. 7C
is another plane view of the same dry chemical analysis element
1
, but provided with only an insufficient amount of the liquid sample dripped thereon. In
FIGS. 7B and 7C
, the cross-hatched portions P
1
and P
2
indicate the reacted portions where the color reaction has occurred.
FIG. 8
is a schematic view showing a possible structure of an existing photometric head
50
for measuring the optical density of the reacted portion
Endo Yoichi
Komatsu Akihiro
Seto Yoshihiro
Sugaya Fumio
Tokiwa Nobuaki
Alexander Lyle A.
Fuji Photo Film Co. , Ltd.
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