What is the clinical evidence from this study?

Study design: Observational. Population: Aspirin therapy (n=72). Intervention: Platelet function tests (PFA-100, VerifyNow-ASA, LTA) vs. Baseline tests. Primary outcome: Within-test agreement of aspirin non-responsiveness at baseline vs 1 year (PFA-100) (kappa 0.44, 95% CI 0.19-0.68, p=0.0006).

What question did this study set out to answer?

This research aims to evaluate the reproducibility of aspirin responsiveness measurements using three different platelet function tests over one year.

January 1, 2008Platelets

Lack of reproducibility of assessment of aspirin responsiveness by optical aggregometry and two platelet function tests

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Key result

Reproducibility of aspirin non-responsiveness over 1 year was moderate for PFA-100 (kappa 0.44) and VerifyNow-ASA (kappa 0.34), and poor for LTA (kappa 0.14).

Why the study?

Are platelet function tests (PFA-100, VerifyNow-ASA, LTA) reproducible over time for assessing aspirin responsiveness in patients on low-dose aspirin?

Population

72 patients who were alive and still receiving low dose aspirin (ASA) therapy one year after initial testing

Comparison

Platelet function testing using PFA-100… vs Baseline platelet function testing using the…

Design

Cohort

Follow-up

1 year

Authors

PHPaul HarrisonCross-Cutting Cardiology HSHelen SegalGeorgetown University LSL E SilverKaiser Permanente

Discussion

Member takes

Implication

Inconsistent reproducibility of platelet function tests over 1 year cautions against routine clinical use for aspirin monitoring; leaves open their value for outcome prediction in future studies.

Key Points

This research aims to evaluate the reproducibility of aspirin responsiveness measurements using three different platelet function tests over one year.
Re-tested 72 patients on low dose ASA therapy one year after initial tests using identical methods.
Measured platelet function with PFA-100, VerifyNow-ASA, and light transmission aggregation (LTA).
Compared results from baseline to one year with kappa statistics for agreement.
Prevalence of non-responsiveness: 10% (VerifyNow-ASA), 25% (PFA-100), and 1% (LTA) at one year.
Agreement between tests at one year was poor (kappa: 0.02-0.17).
Only moderate reproducibility for VerifyNow-ASA (kappa = 0.34, p = 0.12) and fair for PFA-100 (kappa = 0.44, p = 0.0006).

Study Design

Type

Observational (n=72)

Structured PICO

Are platelet function tests (PFA-100, VerifyNow-ASA, LTA) reproducible over time for assessing aspirin responsiveness in patients on low-dose aspirin?

Population

72 patients receiving low dose aspirin therapy re-tested after 1 year to assess the reproducibility of platelet function tests.

Exposure

Platelet function testing using PFA-100, VerifyNow-ASA, and light transmission aggregation (LTA) at 1 year follow-up

Comparator

Baseline platelet function testing using the same methods

Outcome

Reproducibility of aspirin non-responsiveness identification over time (baseline vs 1 year) and agreement between testssurrogate

Main Result

Effect estimate: kappa 0.44 (95% CI 0.19-0.68)

p-value: p=0.0006

The lack of consistency over time in identifying aspirin non-responsiveness undermines the clinical utility of these platelet function tests for predicting recurrent vascular events.

Cite This Study

Harrison et al. (2008) conducted an observational in Aspirin therapy (n=72). Platelet function tests (PFA-100, VerifyNow-ASA, LTA) vs. Baseline tests was evaluated on Within-test agreement of aspirin non-responsiveness at baseline vs 1 year (PFA-100) (kappa 0.44, 95% CI 0.19-0.68, p=0.0006). Reproducibility of aspirin non-responsiveness over 1 year was moderate for PFA-100 (kappa 0.44) and VerifyNow-ASA (kappa 0.34), and poor for LTA (kappa 0.14).

synapsesocial.com/papers/6a6ac166547974b2dbf41ef2 https://doi.org/10.1080/09537100701771736

Topics

Dual antiplatelet therapy

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Implication

Inconsistent reproducibility of platelet function tests over 1 year cautions against routine clinical use for aspirin monitoring; leaves open their value for outcome prediction in future studies.