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The Ultegra® Rapid Platelet Function Assay-ASA (RPFA-ASA) is a qualitative test to aid in the detection of platelet dysfunction due to aspirin (ASA) ingestion in citrated whole blood for the point of care or laboratory setting.

Not for use in patients with underlying congenital platelet abnormalities, patients with non-ASA induced acquired platelet abnormalities or in patients receiving non-ASA anti-platelet agents (may be used in patients treated with selective COX-2 inhibitors, e.g., celecoxib (Celebrex®) and rofecoxib (Vioxx®)).

The Ultegra System is a turbidimetric based optical detection system which measures platelet induced aggregation as an increase in light transmittance. The system consists of a stand-alone analyzer and disposable test cartridge with reagents based on microbead agglutination technology. The quality control system includes an electronic control and two levels of liquid control. The analyzer controls assay sequencing, establishes the assay temperature, controls the reagent-sample mixing for the required duration, determines the degree of platelet function, displays the results and status information to the user, and performs self-diagnostics.

The test cartridge contains a lyophilized preparation of human fibrinogen coated beads, platelet agonist, buffer, and preservative. The patient sample is citrated whole blood, which is automatically dispensed from the blood collection tube into the test cartridge by the analyzer, with no blood handling required by the user. Fibrinogen-coated microparticles are used in the Ultegra RPFA-ASA cartridge to bind to available platelet receptors. When the activated platelets are exposed to the fibringgen-coated microparticles, agglutination occurs in proportion to the number of available platelet receptors. To ensure consistent and uniform activation of the platelets, cationic propyl gallate (c-PG) is incorporated into the assay cartridge to induce platelet activation without fibrin formation. The Ultegra Analyzer is designed to measure this agglutination as an increase in light transmittance. Utregra RPFA-ASA Assay results are reported as Aspirin Reaction Units (ARU).

Acceptance Criteria and Device Performance Study for Accumetrics Ultegra® System Rapid Platelet Function Assay -ASA (RPFA-ASA)

1. Table of Acceptance Criteria and Reported Device Performance

Note: The document does not explicitly state numerical acceptance criteria for sensitivity and specificity. The implied criteria are that the device performance should be acceptable for its intended use as a qualitative test to aid in the detection of platelet dysfunction due to aspirin ingestion.

2. Sample Size and Data Provenance

• Test Set Sample Size:
  • "ASA Present" group (Post-ASA): 143 samples
  • "ASA Absent" group (Pre-ASA): 140 samples
  • Total Patients: 148 patients (each patient provided samples at two time points: pre-ASA and post-ASA).
• Data Provenance:
  • Country of Origin: Not specified in the provided document, but the study was a multi-center clinical trial.
  • Retrospective or Prospective: Prospective. Samples were obtained from subjects before and after aspirin ingestion as part of the trial design.

3. Number of Experts Used to Establish Ground Truth & Qualifications

Not applicable. The ground truth for this study was established based on documented aspirin ingestion status, not expert interpretation of results.

4. Adjudication Method for the Test Set

Not applicable. The ground truth was based on the aspirin ingestion status of the patients. The device results (ARU < 550 for positive, ARU ≥ 550 for negative) were compared directly against this ground truth. There was no mention of human adjudication of device results itself.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, an MRMC comparative effectiveness study was not done. This device is a standalone diagnostic assay designed to measure platelet function, not to assist human readers in interpreting images or other data that typically require MRMC studies.

6. Standalone Performance Study

Yes, a standalone performance study was done. The performance metrics (sensitivity and specificity) represent the algorithm's (device's) ability to correctly classify samples based on the designated cutoff of 550 ARU without human intervention in the interpretation of the ARU value.

7. Type of Ground Truth Used

The ground truth used was aspirin ingestion status. Patients were classified as "ASA Present" if they had ingested 325 mg of aspirin 2 to 30 hours prior to sample collection, and "ASA Absent" if samples were collected prior to aspirin ingestion.

8. Sample Size for the Training Set

The document does not explicitly state the sample size for a dedicated "training set". The performance characteristics were evaluated in a "multi-center clinical trial" where subjects provided samples before and after aspirin ingestion. It is possible that the cutoff of 550 ARU was determined based on an initial analysis of these or similar data, but the breakdown into distinct training and test sets is not provided in detail. The presented concordance table and metrics appear to be from the evaluation of the final device performance.

9. How the Ground Truth for the Training Set Was Established

As with the test set, the ground truth for any potential "training set" (or for the determination of the 550 ARU cutoff) would have been established based on the aspirin ingestion status of the subjects. This involves knowing whether a patient had ingested aspirin (e.g., a 325 mg dose) and the timing relative to sample collection.

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