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510(k) Data Aggregation
(193 days)
The Chrono-log WBA, Model 591A/592A is intended for determination of platelet function in a whole blood specimen, using ADP, Collagen and Ristocetin reagents.
For Platelet Function testing of Whole Blood specimens using Impedance Aggregometry. For Prescription Use.
The Chrono-log WBA, Model 591A/592A uses electrical impedance to measure platelet aggregation in a whole blood sample. The Impedance is measured using a Disposable electrode with two precious metal pins. A small voltage is applies across these two pins. When the electrode is placed into a diluted whole blood specimen and a monolayer is formed around the two pins. In the absence of an agonist, the platelet build-up stabilizes and a baseline is established. When an agonist is added to the specimen, the platelets begin to aggregate and collect on the electrode pins causing a change in impedance. The change of impedance is directly proportional to the amount of Aggregation in the specimen. This change of impedance is displayed on a front panel readout. The instrument has an analog output which produces an aggregation curve when connected to a strip chart recorder or AGGRO/LINK interface. Model 591 A is a single channel version; Model 592A is the duel channel version.
This document describes the performance testing of the Chrono-log Whole Blood Aggregometer (WBA), Model 591A/592A, and its substantial equivalence to the predicate device, Model 591/592, with the primary difference being the introduction of disposable electrodes.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria were primarily based on demonstrating substantial equivalence to the predicate device through correlation, statistical significance, and the ability to detect aggregation changes and patient conditions similarly. New normal ranges were also established.
| Acceptance Criteria / Performance Metric | Predicate Device (Reusable Electrodes) | New Device (Disposable Electrodes) | Reported Performance (New vs. Predicate) | Outcome / Acceptance |
|---|---|---|---|---|
| Overall Correlation (Pearson's R) | N/A | N/A | R = 0.84 (250 samples) | Met |
| Paired t-test | N/A | N/A | P < 0.0001 (250 samples) | Met |
| Reproducibility (Collagen 2μg/mL) | Mean: 13.9 ± 3.0 Ω | Mean: 14.2 ± 2.2 Ω | P = 0.47, R = 0.24 (n=50) | Comparable |
| Reproducibility (Collagen 5μg/mL) | Mean: 17.7 ± 2.8 Ω | Mean: 16.6 ± 2.3 Ω | P = 0.03, R = 0.04 (n=50) | Comparable |
| Reproducibility (ADP 20μM) | Mean: 9.94 ± 3.4 Ω | Mean: 13.2 ± 2.5 Ω | P < 0.01, R = 0.61* (n=50) | Comparable |
| Ristocetin (vWD detection, low dose) | Reduced/absent results for all patients | Reduced/absent results for all patients | Expected for all vWD patients (8/8 for RP, 7/8 for DP showed reduced results) | Met |
| Ristocetin (vWD detection, high dose) | Reduced/absent for vWD patients | Reduced/absent for vWD patients | Better performance for DP in identifying vWD | Met |
| Detecting changes with platelet count (Whole Blood) | Positive correlation (R^2 = 0.4491) | Positive correlation (R^2 = 0.9037) | Both methods demonstrated ability to detect changes | Met |
| Detecting changes with platelet count (PRP) | Positive correlation (R^2 = 0.9064) | Positive correlation (R^2 = 0.8512) | Both methods demonstrated ability to detect changes | Met |
| Normal Range (Collagen 5μg/mL) | 16-29 Ω | N/A | New established: 12-23 Ω | Established / Close to predicate |
| Normal Range (Collagen 2μg/mL) | N/A | N/A | New established: 10-21 Ω | Established |
| Normal Range (ADP 20μM) | 9-14 Ω (for 10μM) | N/A | New established: 9-18 Ω | Established / Close to predicate |
| Normal Range (Ristocetin 0.4mg/mL) | 17-38 Ω (for 1mg/mL) | N/A | New established: >5 Ω | Established / Close to predicate |
Note on R for ADP 20μM: The Pearson's R value of 0.61 is marked with an asterisk indicating p<0.05, suggesting a statistically significant correlation despite the moderate value. The p<0.01 for the paired t-test indicates a statistically significant difference between the means, but the purpose of this study is primarily to show comparable performance and the ability to detect aggregation, not identical readings.
2. Sample Size Used for the Test Set and Data Provenance
- Overall Correlation Study: 250 samples.
- Reproducibility, Precision, and Accuracy (Collagen, ADP): n=50 for each agonist concentration.
- Ristocetin Studies (Normal & vWD Patients): n=12 normal donors, n=8 vWD patients.
- Platelet Count Correlation (Whole Blood & PRP): Specific numbers for each data point are provided in the tables (e.g., 13 data points for Whole Blood, 9 for PRP), but an overall sample size for these specific correlation analyses is not explicitly stated as a single number.
- Data Provenance: The subjects were "normal, healthy, drug free subjects" and "patients known to have von Willebrands Disease (vWD)". The country of origin is not specified but implicitly assumed to be the United States, given the FDA filing. The data is prospective, as it was collected for the purpose of this 510(k) submission to compare the new device with the predicate.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and the Qualifications of Those Experts
The concept of "ground truth" in this context is based on the measurements obtained from the predicate device (Chrono-log Whole Blood Aggregometer Model 591/592) and established medical understanding of platelet aggregation in normal individuals and those with conditions like von Willebrand's Disease. No external "experts" were explicitly used to establish a separate ground truth for the test set beyond the predicate device's readings and known clinical characteristics of patient groups.
4. Adjudication Method for the Test Set
No explicit adjudication method is mentioned. The comparison is objective, based on direct readings from two different devices (new vs. predicate) using the same blood samples and reagents. Statistical tests (Pearson Correlation, Paired t-test) were used to analyze the agreement and differences between the two devices.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study focuses on the performance of the device itself (new electrode vs. old electrode) rather than how human readers (users) interact with or interpret the results, or the impact of AI assistance.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the study is essentially a standalone performance assessment of the new device (model 591A/592A with disposable electrodes) compared to the predicate device (model 591/592 with reusable electrodes). The output is a numerical measurement (aggregation in ohms), and the performance comparison is based on these objective measurements, demonstrating the device's inherent functionality.
7. The Type of Ground Truth Used
The ground truth is primarily:
- Predicate Device Performance: The measurements obtained from the predicate Chrono-log Whole Blood Aggregometer (Model 591/592) served as the primary reference for comparison. The new device was expected to produce "comparable results."
- Known Physiological Responses: The expected aggregation patterns in "normal, healthy, drug-free subjects" and patients with "von Willebrand's Disease (vWD)" were used as a clinical ground truth for assessing the device's ability to differentiate these conditions.
- Clinical Understanding of Platelet Count Impact: The knowledge that platelet aggregation is influenced by platelet count (e.g., reduced aggregation below 50,000/uL) served as a physiological ground truth.
8. The Sample Size for the Training Set
No specific "training set" is mentioned in the context of machine learning. This device operates based on electrical impedance principles, not a machine learning algorithm that requires a training set. The data presented demonstrates the device's performance directly.
9. How the Ground Truth for the Training Set Was Established
Not applicable, as there is no machine learning model or "training set" in the context of this device's validation.
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