Assay Device Internal Standard Quantitative Analysis
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Solution Overview
Problem
Existing assay devices for biological fluid samples often fail to provide accurate quantitative measurements due to inaccuracies from temperature, air moisture, flow time variations, strip-to-strip variations, and signal strength variations, while most devices only determine the presence or absence of an analyte without providing a reliable quantity.
Innovation Solution
A solid phase chromatographic assay device and method that uses a sandwich assay with analytes bound to a label conjugate and capture reagents in test bands, along with standard bands of immobilized calibrator agents, allowing for accurate concentration measurement by comparing the relative intensity of label-bound reagents in both test and standard bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional test strip assay devices are used to detect analytes, then the presence or absence of analytes can be determined, but accurate quantitative measurement is not provided due to variations in temperature, moisture, flow time, and signal strength
Solution Approach 1:
The patent introduces an internal standard component as an intermediary reference element on the test strip. This internal standard contains a known concentration of analyte and serves as a mediator for comparison against the test sample. By comparing the signal intensity between the test sample and the internal standard, the system compensates for variations in temperature, moisture, flow time, and signal strength, thereby achieving accurate quantitative measurement despite environmental fluctuations.
Solution Approach 2:
The patent employs parameter changes by measuring signal intensity ratios between test and standard bands rather than absolute signal values. This approach transforms the measurement from being sensitive to environmental parameters (temperature, humidity, flow time) to being based on relative comparisons. The ratio of signal intensities remains constant across varying conditions, enabling reliable quantitative analysis.
2Ease of operation
If test strips with single-step visual reading are used, then ease of operation is improved, but quantitative measurement capability is lost
Solution Approach 1:
The patent merges the advantages of both qualitative and quantitative assay approaches into a single integrated test strip system. The test strip maintains the simple single-step visual reading format for ease of operation while incorporating internal standard bands that enable quantitative measurement. The system combines the user-friendly interface of qualitative tests with the analytical capability of quantitative assays through automated optical scanning and ratio-based calculation.
Solution Approach 2:
The test strip is designed with multi-functionality, serving both qualitative detection (presence/absence determination) and quantitative measurement (concentration analysis) purposes. The same test strip structure with immobilized ligands and internal standards can perform both functions, eliminating the need for separate qualitative and quantitative testing procedures.
3Measurement precision
If standard curves with known concentrations are used for quantification, then measurement accuracy can be improved, but device complexity and susceptibility to environmental variations increase
Solution Approach 1:
The patent extracts the calibration function from external standard curves and environmental conditions and embeds it directly into the test strip itself through the internal standard component. Instead of requiring separate calibration procedures or external reference standards, the internal standard is integrated onto the same strip as the test sample, containing known concentrations of analyte that serve as built-in calibration references. This eliminates the complexity of external calibration while maintaining measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, efficient, and accurate quantitative analysis of fluid samples with low background noise, capable of detecting and quantitating analytes in small volumes, and separating cells from fluids, providing reliable concentration measurements.
Implementation Method 1
The test strip allows the label-bound analyte to move by capillary action to a sample capture zone where the analyte complex is retained by virtue of being bound to the immobilized capture ligand
Implementation Method 2
commercially available optical readers can convert the reflected light intensity of the sample into concentration as measured on the basis of the curve derived from the reflected intensity of the standard bands of known concentrations
Data Source
AI summary
There is disclosed an assay device for the quantitative determination of an analyte, comprising a test strip containing a porous test membrane allowing for capillary flow of the analyte and complexes of the analyte, a porous upstream membrane in fluid connection with the test membrane and a porous downstream membrane in fluid connection with the test membrane, (a) said test membrane containing a test site having immobilized thereon a ligand capable of reacting with the analyte and binding such to the test site, and two standard band sites having immobilized thereon known high and low concentrations of a calibrator agent capable of reacting with a label conjugate and binding such to the standard sites, (b) said upstream membrane having a site for the application of a sample to be analyzed and having a site downstream from the sample application site for depositing label conjugates capable of reacting with the analyte and label conjugates capable of reacting with the immobilized calibrator agents in the standard bands to provide a known label response in the standards bands, and (c) said downstream membrane capable of absorbing said sample and providing the capillary flow for the sample through the upstream and test membrane.