CHRONO-LOG WHOLE BLOOD AGGREGOMETER, MODELS 591A AND 592A

K032951 · Chrono-Log Corp. · JOZ · Apr 2, 2004 · Hematology

Device Facts

• Record ID: K032951
• Device Name: CHRONO-LOG WHOLE BLOOD AGGREGOMETER, MODELS 591A AND 592A
• Applicant: Chrono-Log Corp.
• Product Code: JOZ · Hematology
• Decision Date: Apr 2, 2004
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 864.5700
• Device Class: Class 2

Indications for Use

The Chrono-log Whole Blood Aggregometer (WBA) Model 591A/592A is intended for determination of platelet function in a whole blood specimen, using ADP, Collagen and Ristocetin reagents. The Chrono-log WBA Model 591A/592A is for platelet function testing of whole blood specimens using Impedance Aggregometry.

Device Story

The Chrono-log WBA Model 591A/592A measures platelet aggregation in citrated whole blood via electrical impedance. The device uses a disposable gold-plated square electrode assembly inserted into a cuvette containing blood heated to 37°C. A stirbar maintains sample homogeneity. As platelets aggregate on the electrode pins following the addition of agonists (ADP, Collagen, or Ristocetin), the electrical current in the sample decreases. The device converts this change in current into an impedance measurement (Ohms), which is displayed digitally or recorded on a strip chart. Used in clinical laboratory settings, the device provides quantitative data to assist clinicians in evaluating platelet function and diagnosing conditions like von Willebrand Disease. The disposable electrode design replaces the reusable palladium electrode of the predicate, with the limitation that it is not compatible with Arachidonic Acid.

Clinical Evidence

Clinical evidence includes method comparison studies between disposable and reusable electrodes. A study of 50 normal subjects (35 female, 15 male) using all agonists showed a correlation of r=0.79 (p<0.01). A larger study (N=250) using ADP and collagen showed r=0.84 (p<0.0001). Matrix comparison studies in whole blood and platelet-rich plasma were conducted. Sensitivity to von Willebrand Factor deficiency was demonstrated using Ristocetin in patients with von Willebrand Disease. Reference ranges were established in 50 donors, showing no significant difference from the predicate.

Technological Characteristics

Impedance-based platelet aggregation system. Disposable electrodes consist of two precious metal pins. Features automatic baseline setting, front panel digital readout, and analog output for external recording. Single-channel (591A) or dual-channel (592A) configurations. Operates via electrical impedance measurement of platelet build-up on electrode pins. No software algorithm described; device relies on analog signal processing and direct impedance measurement.

Indications for Use

Indicated for platelet function testing of whole blood specimens using impedance aggregometry. Intended for prescription use.

Regulatory Classification

Identification

An automated platelet aggregation system is a device used to determine changes in platelet shape and platelet aggregation following the addition of an aggregating reagent to a platelet-rich plasma.

Predicate Devices

• Chrono-log Whole Blood Aggregometer (WBA) Model 591/592 (K962426)

Submission Summary (Full Text)

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
DEVICE ONLY TEMPLATE

A. 510(k) Number: #K032951
B. Analyte: Platelet aggregometry
C. Type of Test: Quantitative
D. Applicant: Chrono-log Corporation
E. Proprietary and Established Names: Whole Blood Aggregometer (WBA), Model 591A/592A

F. Regulatory Information:
1. Regulation section: CFR Section 864.5700 – Automated Platelet Aggregation System
2. Classification: Class II
3. Product Code: JOZ
4. Panel: Hematology (81)

G. Intended Use:
1. Intended use(s):
The Chrono-log Whole Blood Aggregometer (WBA) Model 591A/592A is intended for determination of platelet function in a whole blood specimen, using ADP, Collagen and Ristocetin reagents.
2. Indication(s) for use: The Chrono-log WBA Model 591A/592A is for platelet function testing of whole blood specimens using Impedance Aggregometry.
3. Special condition for use statement(s): N/A
4. Special instrument Requirements: N/A

H. Device Description: The Model 591A/592A WBA is a modified version of their single and dual channel Model 591/592 WBA. The new model employs the use of a gold plated disposable electrode, while the current model uses a palladium reusable electrode. Other changes are the probe’s method of connection, size and square shape, instead of the round shape of the reusable electrode. The disposable probe is not for use with the agonist, Arachidonic Acid (AA), as is the reusable electrode.

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I. Substantial Equivalence Information:

1. Predicate device name(s): Chrono-log WBA, Model 591/592
2. Predicate K number(s): #K962426
3. Comparison with predicate:

| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Principle of Operation | Electrical impedance | Same |
| Sample type | Citrated whole blood | Same |
| Calibration | Electrical | Same |
| Channels | Single and dual | Same |
| Test results | Ohms | Same |
| Readout | Digital w/optical chart reader | Same |
| Differences | | |
| Item | Device | Predicate |
| Type/shape of electrode | Gold plate/square | Palladium/round |
| Method of connection | Attached to copper traces embedded on a flexible Kapton sheet | Soldered to a printed circuit board, coated with non-conductive polyurethane |
| Size of electrode | 0.01 x 0.01 x 0.2 inches | 0.01 x 0.24 inches |
| Agonists used | Only ADP, Collagen and Ristocetin | Arachidonic acid, ADP, Collagen and Ristocetin |

J. Standard/Guidance Document Referenced (if applicable): N/A

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K. Test Principle: Both Models of the Chrono-log WBA use electrical impedance to measure platelet aggregation in citrated whole blood. The electrode assembly is placed into a cuvette containing whole blood, and is then heated to $37^{\circ}\mathrm{C}$. A stirbar is spun to stir the sample, during which a layer of platelets builds up on the electrode pins. The electric circuit monitors the current in the sample, and upon stabilization, a baseline is established. The circuit converts the current into an impedance measurement. The agonist is added to the sample, upon which platelets aggregate and gather on the electrode tip. The sample current is reduced and converted, by the circuit, into an impedance change. That change is directly related to the amount of aggregation in the sample. It is then converted into a numeric readout, as a change of impedance in Ohms, or recorded on a strip chart recorder.

L. Performance Characteristics (if/when applicable): N/A

1. Analytical performance:
a. Precision/Reproducibility:
b. Linearity/assay reportable range:
c. Traceability (controls, calibrators, or method):
d. Detection limit:
e. Analytical specificity:
f. Assay cut-off

2. Comparison studies:
a. Method comparison with predicate device: A clinical probe comparison study was performed at Miriam Hospital on whole blood samples $(N=50)$ from normal subjects, using all agonists. Females $(N=35)$ and males $(N=15)$ yielded correlation between the two probes of $r = 0.79$. The 'p' value was $&lt; 0.01$.
An additional comparison study between the two electrodes, using ADP and collagen on normal samples $(N = 250)$, was performed. That study yielded $r = 0.84$; and a 'p' value of $&lt; 0.0001$.
b. Matrix comparison: A study performed with disposable and reusable electrodes in whole blood (WB) and platelet rich plasma (PRP) samples (with decreasing platelet counts) generated these results:

WB - R2 = 0.9037 (Disposable); R2 = 0.4491 (Reusable)
PRP - R2 = 0.8512 (Disposable); R2 = 0.9064 (Reusable)

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3. Clinical studies:
a. Clinical sensitivity:
b. Clinical specificity:
c. Other clinical supportive data (when a and b are not applicable):
The company also supplied studies of the probes in normal samples, along with Bland-Altman plots, using ADP and collagen agonists; and with the Ristocetin agonist in patients with von Willebrand Disease (vWD) to demonstrate the probe’s sensitivity to von Willebrand Factor deficiency.

4. Clinical cut-off: 5 Ohms

5. Expected values/Reference range: The normal range study for the disposable electrode was performed on donors (N = 50), with agonists ADP, collagen and Ristocetin. The following results were not significantly different from the reusable electrode’s reference values:

| Agonist | Concentration | Aggregation (Ohms) |
| --- | --- | --- |
| ADP | 20 uM | 9 – 10 |
| Collagen | 5 ug/mL | 12 – 23 |
| Ristocetin | 0.4 mg/mL | > 5 |

M. Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.