Coagulation Test Correction for Underfilled Samples

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Solution Overview

Problem

Underfilled sample tubes in coagulation testing disrupt the sodium citrate ratio, leading to significant alterations in coagulation test results, particularly for prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen levels, causing delays in obtaining accurate clinical assessments and potentially denying timely anti-thrombotic therapies.

Innovation Solution

A method to estimate coagulation test results from underfilled samples by determining the percent fill, correcting the sample volume with a diluent, and applying a percent-fill-dependent correction factor to generate an estimated coagulation test value, using correction factors derived from population averages to normalize results as if the sample were properly filled.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If underfilled sample tubes are used in coagulation testing, then sample collection time is reduced and patient throughput is improved, but measurement precision and test result accuracy deteriorate due to disrupted sodium citrate ratio

Engineering Contradiction:

Improvepatient throughputVSAvoidcoagulation test result accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by introducing a percent-fill-dependent correction factor that varies based on the sample fill volume. This correction factor adjusts the measured coagulation test values (PT, aPTT, fibrinogen) to compensate for the disrupted sodium citrate ratio in underfilled samples. The correction factor is calculated based on the ratio of actual sample volume to expected sample volume, transforming the inaccurate measurements into corrected values that reflect what would have been obtained with proper fill volume.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/physical requirement of proper sample fill volume with a computational correction system. Instead of relying on the physical constraint of correct tube filling to ensure accurate results, the system substitutes a mathematical correction approach that processes the measured values and adjusts them based on the actual fill percentage, thereby eliminating the need for strict mechanical adherence to fill volume requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If underfilled samples are discarded and redrawn, then measurement precision is maintained, but loss of time occurs due to delayed clinical assessment and treatment decisions

Engineering Contradiction:

Improvecoagulation test result accuracyVSAvoidtime to obtain clinical assessment

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent converts the harmful effect of underfilling (disrupted sodium citrate ratio leading to inaccurate results) into a beneficial situation by using the degree of underfilling as the basis for a correction factor. The harm of inaccurate measurements is transformed into a quantifiable parameter (percent fill) that drives the correction algorithm, allowing the system to recover accurate results from what would traditionally be considered defective samples.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent performs preliminary correction of the coagulation test values based on the measured fill percentage before final result reporting. By applying the correction factor in advance to the raw measurements, the system proactively compensates for the fill volume error, ensuring that the corrected values presented to clinicians are already adjusted for accuracy without requiring sample rejection or redraw.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If correction factors are applied to underfilled samples, then productivity is improved by avoiding redraws, but measurement precision may deteriorate if correction accuracy is insufficient

Engineering Contradiction:

Improvesample processing efficiencyVSAvoidcorrected result accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the actual sample fill volume (determined by comparing measured sample volume to expected volume) feeds into the correction factor calculation. This feedback loop allows the system to dynamically adjust the correction applied to each sample based on its specific underfill degree, ensuring that the correction is neither over-applied nor under-applied. The correction factor is directly derived from the fill percentage, creating a closed-loop system that adapts to each sample's conditions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10976305B2Coagulation testing in underfilled patient samples

Publication Date: 2021.04.13 UNIVERSITY OF CHICAGO

AI summary

Provided herein are methods for generating an estimated coagulation test result from an underfilled sample tube.