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The VerifyNow Aspirin Assay is a qualitative assay to aid in the detection of platelet dysfunction due to aspirin ingestion in citrated whole blood for the point of care or laboratory setting.

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

The VerifyNow 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 instrument and disposable assay device with reagents based on microbead agglutination technology. The quality control system includes an electronic quality control, an assay device internal control, and two levels of external, wet quality control controls. The instrument controls assay sequencing, establishes the assay temperature, controls the reagentsample 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 assay device contains a lyophilized preparation of human fibrinogen coated beads, platelet agonist, a peptide, bovine serum albumin, buffer, and stabilizer. The patient sample is citrated whole blood, which is automatically dispensed from the blood collection tube into the assay device by the instrument, with no blood handling required by the user. Fibrinogen-coated microparticles are used in the VerifyNow-Aspirin assay device to bind activated platelet GP IIb/Ila receptors. When the activated platelets are exposed to the fibrinogen-coated microparticles, aggregation occurs in proportion to the number of activated platelet receptors. To ensure consistent and uniform activation of the platelets, the agonist arachidonic acid is incorporated into the assay device. The VerifyNow-Aspirin Assay reports results in Aspirin Reaction Units (ARU).

Acceptance Criteria and Device Performance Study for VerifyNow-Aspirin Assay

This document summarizes the acceptance criteria for the VerifyNow-Aspirin Assay and the study conducted to demonstrate the device meets these criteria, based on the provided 510(k) summary.

1. Table of Acceptance Criteria and Reported Device Performance

The provided document does not explicitly state pre-defined acceptance criteria in terms of specific performance thresholds for sensitivity and specificity. However, the reported performance results can be interpreted as the achievement for acceptance.

Note: The acceptance criteria are "implied" because the document states "The VerifyNow-Aspirin Assay was evaluated against the presence and absence of aspirin ingestion. The concordance table below illustrates performance results." This suggests that the reported numbers were deemed acceptable by the FDA for substantial equivalence.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set:

  • Total subjects: 136
  • Subjects tested before and after 325 mg aspirin ingestion: 71
  • Subjects on chronic 81 mg/day aspirin therapy (single post-aspirin time point): 65
  • Total number of individual test results in the concordance table: 245 (Aspirin Present) + 0 (Aspirin Present, Negative result) + 23 (Aspirin Absent, Positive result) + 141 (Aspirin Absent, Negative result) = 409 test results. These results are derived from the 136 subjects.

• Data Provenance: The study was a "multi-center clinical trial." The country of origin is not explicitly stated, but given the FDA 510(k) submission, it is highly likely the data includes or originates from studies conducted in the United States. The data is prospective as subjects were recruited and tested specifically for the study.

3. Number of Experts and Qualifications for Ground Truth

The document does not specify the number of experts used or their qualifications to establish the ground truth for the test set.

4. Adjudication Method for the Test Set

The document does not specify an adjudication method (e.g., 2+1, 3+1, none) for the test set. The ground truth ("Aspirin State: Present / Absent") appears to be determined by documented aspirin ingestion or lack thereof.

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

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly described. The study evaluated the standalone performance of the VerifyNow-Aspirin Assay against the patient's aspirin status, not against human reader performance with or without AI assistance.

6. Standalone Performance Study

Yes, a standalone (i.e., algorithm only without human-in-the-loop performance) study was performed. The reported sensitivity and specificity values are for the VerifyNow-Aspirin Assay itself, with its specified cutoff of 550 ARU, in determining aspirin ingestion status.

7. Type of Ground Truth Used

The type of ground truth used was documented aspirin ingestion status. Subjects were classified as "Aspirin Present" if they had ingested aspirin (either 325mg before testing or chronic 81mg/day therapy) or "Aspirin Absent" if they had not ingested aspirin. This is a direct measure based on treatment, not expert consensus, pathology, or outcomes data in this context.

8. Sample Size for the Training Set

The document does not explicitly state a separate sample size for a training set. The clinical trial described appears to be the primary dataset for performance evaluation. It is possible that the cutoff of 550 ARU was determined from a portion of this data or prior developmental studies, but this is not detailed.

9. How Ground Truth for the Training Set Was Established

As a separate training set is not explicitly mentioned, the method for establishing ground truth for any potential internal training or development would likely be the same as for the test set: documented aspirin ingestion status of the subjects.

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