The diaDexus PLAC® test is an enzyme immunoassay for the quantitative determination of Lp-PLA2 (lipoprotein-associated phospholipase A2) in human plasma and serum, to be used in conjunction with clinical evaluation and patient risk assessment as an aid in predicting risk for coronary heart disease, and ischemic stroke associated with atherosclerosis.

Device Description

The diaDexus PLAC® test kit contains Lp-PLA2 calibrators, monoclonal anti-Lp-PLA2 (4B4) antibody conjugated to horseradish peroxidase, monoclonal anti-Lp-PLA2 (2C10) antibody-coated microwell strips with a stripwell frame, various buffers and related reagents, and a package insert. Each stripwell can be used for performing only one set of tests (i.e. single use). One plate may accommodate up to 40 clinical samples when assayed in duplicate. The kit expiration date and storage conditions are indicated on the package.

The diaDexus PLAC® test is based on the standard principle of a sandwich enzyme immunoassay using two specific monoclonal antibodies. A set of LD-PLA2 calibrators is used to plot a standard curve of absorbance (y-axis) versus Lp-PLA2 concentration in ng/mL (x-axis) from which the Lp-PLA2 concentration in the test sample can be determined. The concentration of Lp-PLA2 in each sample and control is then interpolated from the standard curve using a point-to-point curve fit with appropriate calibration curve fitting software.

AI/ML Overview

Here's an analysis of the provided text, focusing on the acceptance criteria and the study proving the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance:

Performance Characteristic	Acceptance Criteria (Implied by reported value)	Reported Device Performance
Analytical Sensitivity (Detection Limit)	A low detection limit to accurately measure Lp-PLA2	2.4 ng/mL
Linearity/Assay Range	A specified range for accurate quantitative determination	120 - 782 ng/mL
Interfering Substances	No appreciable interference from common substances at specified concentrations	No appreciable interference from: - Total Albumin ~6500 mg/dL - Bilirubin 20 mg/dL - Cholesterol 500 mg/dL - Hemoglobin 1250 mg/dL - Triglycerides 3000 mg/dL
Intra-assay Precision (n=80)	Low percentage of coefficient of variation (%CV) for within-assay consistency	4.3 %CV to 6.3 %CV
Total Precision (n=80)	Low percentage of coefficient of variation (%CV) for overall consistency	5.7 %CV to 11.0 %CV
Correlation with Cleared PLAC Test (r value)	High correlation (r value close to 1) with the predicate device	0.91
Correlation with Cleared PLAC Test (slope)	Slope close to 1 for close agreement with the predicate device	1.02

Explanation of "Implied by reported value": The document explicitly states the "Reported Device Performance" but does not set a separate, distinct "Acceptance Criteria" for each analytical metric. Instead, the reported values are presented as the device's performance, implying that these values met the internal and regulatory expectations for the assay's function. For instance, the detection limit of 2.4 ng/mL is the accepted performance for this characteristic. The correlation values of 0.91 for r and 1.02 for slope demonstrate good correlation, implicitly meeting the acceptance criteria for equivalence.

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

Sample Size for Analytical Performance Tests:
- Analytical Sensitivity (Detection Limit): 16 replicates of the 0 ng/mL Lp-PLA2 calibrator were used.
- Precision (Intra-assay and Total): n=80 for each precision study.
- Interfering Substances: The exact number of samples for each interfering substance test is not explicitly stated, but the tested concentrations are provided.
Sample Size for Correlation Study: Not explicitly stated, though it refers to "the modified PLAC test compared to the cleared PLAC test."
Data Provenance: The document does not specify the country of origin for the data. The data appears to be prospective for the analytical studies (precision, sensitivity, linearity, interference) as these are part of the device's original characterization. For the correlation study, it compares the current (modified) device to a previously cleared device, suggesting the data for the modified device was prospectively generated for this comparison.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:

Not Applicable. This document describes an in vitro diagnostic (IVD) assay for quantitative determination of a biomarker (Lp-PLA2). The "ground truth" for such devices is established by the accuracy of the assay's measurement against known concentrations (calibrators, controls) and its performance characteristics (precision, linearity, sensitivity, interference). It does not involve expert readers establishing ground truth for diagnostic interpretation of images or clinical cases using the device.

4. Adjudication Method (for the test set):

Not Applicable. As this is an IVD assay measuring a biomarker, there is no expert adjudication method for the analytical performance tests. The "ground truth" for analytical performance relies on accurate measurement technologies, calibrated standards, and statistical methods such as calculating %CV or correlation coefficients.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

Not Applicable. This is an IVD device, not an AI-assisted diagnostic tool that aids human readers in interpreting clinical cases. Therefore, no MRMC study, human reader improvement analysis, or AI assistance effect size is relevant or presented.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done:

Yes, a standalone performance study was done. The entire "Performance Characteristics - Analytical" section describes the standalone performance of the diaDexus PLAC® test. This includes analytical sensitivity, linearity/assay range, interfering substances, and precision. The "Correlation" section also compares the standalone performance of the modified PLAC test to the cleared PLAC test. The device's function is to quantitatively determine Lp-PLA2 levels, which is a standalone measurement without human-in-the-loop diagnostic interpretation in the assay process itself.

7. The Type of Ground Truth Used:

The ground truth used for the analytical performance studies (sensitivity, linearity, precision) is based on calibrated standards and controls with known concentrations of Lp-PLA2.
- For analytical sensitivity, the ground truth is the 0 ng/mL Lp-PLA2 calibrator.
- For linearity/assay range, the ground truth is established by the known concentrations of calibrators used to plot the standard curve.
- For interfering substances, the ground truth is the known concentration of Lp-PLA2 in samples spiked with interfering substances compared to control samples.
- For precision, the ground truth is the expected value of the control samples or patient samples being repeatedly measured.
- For correlation, the ground truth for comparison is the performance of the legally cleared predicate device (K050523).

8. The Sample Size for the Training Set:

Not explicitly stated; likely not applicable in the conventional sense of machine learning training sets. This document describes a traditional enzyme immunoassay (EIA), not a machine learning or AI-based diagnostic algorithm that requires a "training set" of data to learn patterns. The "training" in this context refers to the development and refinement of the assay's reagents and protocol to accurately measure Lp-PLA2. The calibrators and controls are used for routine calibration and quality control, not as a training set for an algorithm.

9. How the Ground Truth for the Training Set was Established:

Not Applicable in the conventional sense. As explained above, this is not an AI/ML device. The "ground truth" for developing and validating the assay relies on:
- Purified recombinant Lp-PLA2 (DDX-RA) characterized for consistency with literature (molecular weight, etc.). This serves as the "true" antigen.
- Monoclonal anti-Lp-PLA2 antibodies characterized for purity and reactivity to quantitatively and specifically bind the Lp-PLA2 antigen.
- Known concentrations of Lp-PLA2 calibrators prepared to establish the standard curve.
- Quality control materials with defined concentrations to monitor assay performance.

Summary

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SEP 1 1 2006

diaDexus, Inc. PLAC® Test Special 510(k) K062234

510(k) Summary diaDexus PLAC® Test

This summary of 510(k) safety and effectiveness information is being submitted in accordance with the requirements of SMDA 1990 and 21 CFR 807.92.

The assigned 510(k) number is: K062234

General Information

Name and Address of Applicant:	diaDexus, Inc.343 Oyster Point Blvd.South San Francisco, CA 94080
Device Trade Name:	diaDexus PLAC® test
Generic Name:	Enzyme Immunoassay for the QuantitativeDetermination of Lp-PLA2 (Lipoprotein-Associated Phospholipase A2) in HumanPlasma and Serum

Intended Use

Device Description

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Characterization of Rare Reagents

Antigen

The antigen used in the diaDexus enzyme immunoassay PLAC® test is purified recombinant Lp-PLA2 (DDX-RA). Antigen preparations were characterized using SDS-polyacrylamide gels under reducing and non-reducing conditions and Western blot analysis using an anti-Lp-PLA2 antibody, to demonstrate consistency with the molecular weight of the antigen reported in the literature.

Antibodies

The monoclonal anti-Lp-PLA2 antibodies used in the preparation of the coated microwell strips (2C10) and conjugate (4B4) were characterized for purity and reactivity in a series of procedures including Paragon gel electrophoresis, SDS-PAGE, size exclusion chromatography, isotyping and enzyme immunoassay. These results demonstrated that the monoclonal antibodies bind to the Lp-PLA2 antigen quantitatively and specifically.

Performance Characteristics - Analytical

Analytical Sensitivity (Detection Limit)

The minimum detection limit is 2.4 ng/mL, as calculated by interpolation of the mean plus two standard deviations of 16 replicates of the 0 ng/mL Lp-PLA2 calibrator.

Linearity/Assay Range

120 - 782 ng/mL

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Interfering Substances

No appreciable interference from the addition of the following substances at the noted concentrations:

Total Albumin ~6500 mg/dL .
. Bilirubin 20 mg/dL
Cholesterol . 500 mg/dL
Hemoglobin . 1250 mg/dL
Triglycerides � 3000 mg/dL

Precision

Intra-assay precision (n=80) ranged from 4.3 %CV to 6.3 %CV throughout assay range.

Total precision (n=80) ranged from 5.7 %CV to 11.0 %CV throughout assay range.

Correlation

The modified PLAC test compared to the cleared PLAC test in a correlation regression resulted in an r value of 0.91 with a slope of 1.02.

Performance Characteristics – Clinical

No new clinical data was generated. The modified PLAC test has the same performance characteristics and clinical utility as the cleared PLAC test (K050523).

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Image /page/3/Picture/0 description: The image shows the text "DEPARTMENT OF HEALTH & HUMAN SERVICES". The text is in all caps and is in a bold, sans-serif font. The text is centered horizontally and vertically in the image. The background of the image is white.

Public Health Service

SEP 1 1 2006

Food and Drug Administration 2098 Gaither Road Rockville MD 20850

Robert L. Wolfert, Ph.D. Executive Vice President of Diagnostics diaDexus, Inc. 343 Oyster Point Blvd. South San Francisco, CA 94080

Re:

K062234 Trade/Device Name: diaDexus PLAC® Test Regulation Number: 21 CFR 866.5600 Regulation Name: Low-density lipoprotein immunological test system Regulatory Class: Class II Product Code: NOE Dated: August 1, 2006 Received: August 23, 2006

Dear Dr. Wolfert:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to such additional controls. Existing major regulations affecting your device can be found in Title 21, Code of Federal Regulations (CFR), Parts 800 to 895. In addition, FDA may publish further announcements concerning your device in the Federal Register.

Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); and good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820).

Image /page/3/Picture/10 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo is circular and contains the words "DEPARTMENT OF HEALTH & HUMAN SERVICES . USA" around the perimeter. Inside the circle is an abstract symbol that resembles an eagle or bird with stylized lines representing its wings and body.

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Page 2 -

This letter will allow you to begin marketing your device as described in your Section 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.

If you desire specific information about the application of labeling requirements to your device, or questions on the promotion and advertising of your device, please contact the Office of In Vitro Diagnostic Device Evaluation and Safety at (240) 276-0484. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21CFR Part 807.97). You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its Internet address http://www.fda.gov/cdrh/industry/support/index.html.

Sincerely yours,

Alberto G

Alberto Gutierrez, Ph.D. Director Division of Chemistry and Toxicology Office of In Vitro Diagnostic Device Evaluation and Safety Center for Devices and Radiological Health

Enclosure

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Indications for Use

510(k) Number: K062234

Device Name:

diaDexus PLAC® Test

Indications For Use:

Prescription Use X (Part 21 CFR 801 Subpart D)

AND/OR

Over-The-Counter Use (21 CFR 801 Subpart C)

(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)

Concurrence of CDRH, Office of In Vitro Diagnostic Devices (OIVD)

Division Sign-Off

Office of in Vitro Diagnostic Device Evaluation and Safety

510(k) K062234

Page 1 of 1

Regulation Number and Section

§ 866.5600 Low-density lipoprotein immunological test system.

(a)
Identification. A low-density lipoprotein immunological test system is a device that consists of the reagents used to measure by immunochemical techniques the low-density lipoprotein in serum and other body fluids. Measurement of low-density lipoprotein in serum may aid in the diagnosis of disorders of lipid (fat) metabolism and help to identify young persons at risk from cardiovascular diseases.(b)
Classification. Class II (performance standards).