The PLAC® Test Reagent Kit is a turbidimetric immunoassay for the quantitative determination of Lp-PLA2 (lipoprotein-associated phospholipase A2) in human plasma or serum on automated clinical chemistry analyzers, 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.

The PLAC® Test Calibrator Kit is intended to establish points of reference that are used in the determination of values in the measurement of Lp-PLA2 by the PLAC® Test Reagent Kit.

The Lp-PLA2 Control Kit is intended for use as a quality control tool to monitor the performance within the clinical range of the PLAC® Test Reagent Kit, a turbidimetric immunoassay for the quantitative determination of Lp-PLA2.

Device Description

The diaDexus PLAC® Test assay consists of separately packaged reagents, calibrators and controls for the measurement of Lp-PLA2 in serum or plasma on automated clinical chemistry analyzers.

PLAC® Test Reagent Kit .
- R1 Tris-based buffer solution
- R2 Suspension of latex microparticles coated with mouse monoclonal antibodies specific to Lp-PLA2 (2C10 and 4B4).
PLAC® Test Calibrator Kit .
Five level set of Lp-PLA2 calibrators made with recombinant Lp-PLA2 in a protein stabilizing buffer and used to calibrate the PLAC assay.
Lp-PLA2 Control Kit .
Two level set of Lp-PLA2 controls made with recombinant Lp-PLA2 in a protein stabilizing buffer and used for quality control of the PLAC assay.

The diaDexus PLAC® Test is based on turbidimetric immunoassay technology utilizing two Lp-PLA2-specific monoclonal antibodies (2C10 and 4B4) coated to latex microparticles. A set of Lp-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 LD-PLA2 in each sample and control is then interpolated from the standard curve using a spline curve fit with appropriate calibration curve fitting software. The kit expiration date and storage conditions are indicated on the package.

AI/ML Overview

Here's a breakdown of the acceptance criteria and study information for the diaDexus PLAC® Test Reagent Kit, based on the provided 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

Parameter	Acceptance Criteria (Implied by Predicate Equivalence)	Reported Device Performance
Sensitivity	Equivalent to predicate (ELISA method)	Minimum detection limit: 4.0 ng/mL
Precision	Equivalent to predicate (ELISA method)	Intra-assay: 1.6 %CV to 2.4 %CV (throughout 69-450 ng/mL range)
		Total precision: 1.8 %CV to 3.2 %CV (throughout 69-450 ng/mL range)
Linearity/Assay Range	Equivalent to predicate (ELISA method)	Average recovery: 97% over a range of 96 to 472 ng/mL
Interfering Substances	No appreciable interference from common substances at specified concentrations	No appreciable interference from Bilirubin (20 mg/dL), Cholesterol (500 mg/dL), Hemoglobin (10,000 mg/dL), Triglycerides (3000 mg/dL), Total Albumin (~6500 mg/dL)
Method Comparison (vs. Predicate)	High correlation (e.g., r > 0.90) and acceptable slope (e.g., close to 1.0)	Correlation coefficient (r) = 0.95; Slope = 1.02

Note on Acceptance Criteria: For this 510(k) submission, the primary acceptance criterion is substantial equivalence to the predicate device (PLAC® Test ELISA kit, K062234). Therefore, the acceptance criteria for the new device's performance characteristics (sensitivity, precision, linearity, interference) are implicitly that they should be comparable to or within acceptable limits relative to the established performance of the predicate device. The method comparison study directly demonstrates this by comparing the new device's results to the predicate's.

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

The document primarily describes analytical performance studies.

Precision study: n=80 (number of replicates for intra-assay and total precision). The data provenance is not specified (e.g., country of origin, retrospective/prospective).
Linearity experiments: The document mentions "linearity experiments" but does not specify the number of samples used.
Interfering substances study: The document identifies specific interfering substances and their concentrations but does not specify the number of samples tested for this.
Method Comparison study: The document states a "correlation study" was performed, comparing the new turbidimetric immunoassay to the cleared ELISA method, resulting in an r-value and slope. However, the sample size for this comparison is not explicitly stated in the provided text.
Data Provenance: Not explicitly stated for any of the analytical studies.

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

N/A. This is an analytical performance study for an in vitro diagnostic test measuring a biochemical analyte (Lp-PLA2). There is no "ground truth" established by human experts in the way it would be for imaging diagnostics or clinical judgment. The ground truth for analytical accuracy is determined by established laboratory methods, standard curves, and comparison to a legally marketed predicate device.

4. Adjudication Method for the Test Set

N/A. As stated above, this is an analytical performance study. Adjudication by experts is not applicable here.

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

N/A. This device is an in vitro diagnostic (IVD) assay, not an AI-powered diagnostic system involving human readers. Therefore, an MRMC comparative effectiveness study is not applicable.

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

Yes, a standalone analytical performance study was done. The precision, sensitivity, linearity, and interference studies demonstrate the performance of the device itself (the assay kit) without human interpretation steps beyond standard laboratory procedures for running an automated clinical chemistry analyzer. The method comparison study also evaluates the standalone performance of the new turbidimetric assay against the predicate ELISA assay.

7. The type of ground truth used

The ground truth for the analytical studies is based on:

Reference standards: Calibrators with known concentrations of recombinant Lp-PLA2 are used to establish standard curves.
Comparison to a legally marketed predicate device: For method comparison, the results obtained from the new device are compared to results obtained from the previously cleared PLAC® Test (ELISA method) (K062234), which serves as the reference or "ground truth" for demonstrating substantial equivalence.

8. The sample size for the training set

N/A. This is a conventional immunoassay kit, not a machine learning or AI-based device that requires a "training set" in the context of algorithm development. The "training set" concept is typically relevant for AI models.

9. How the ground truth for the training set was established

N/A. As this is not an AI/ML device, there is no training set or associated ground truth establishment process in that context. The "ground truth" for developing the assay itself would be based on biochemical characterization of the analyte (Lp-PLA2), purified recombinant Lp-PLA2, and monoclonal antibodies, as mentioned in the "Characterization of Rare Reagents" section.

Summary

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510(k) Summary

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

The assigned 510(k) number is: __K072599

General Information

Name and Address of Applicant diaDexus, Inc. 343 Oyster Point Blvd. South San Francisco, CA 94080

DEC 2 0 2007

Contact Person Julie Blacklock 650-246-6400 Telephone 650-246-6499 Facsimile

Date Prepared September 13, 2007

Trade Name

PLAC® Test Reagent Kit PLAC® Test Calibrator Kit Lp-PLA2 Control Kit

Common Name

Turbidimetric Immunoassay for the Quantitative Determination of Lp-PLA2 (Lipoprotein-Associated Phospholipase A2) in Human Plasma or Serum

Calibrators for use with Lp-PLA2 Turbidimetric Immunoassay

Controls for use with Lp-PLA2 Turbidimetric Immunoassay

Classification Name

TEST, SYSTEM, IMMUNOASSAY, LIPOPROTEIN-ASSOCIATED PHOSPHOLIPASE A2 (21 CFR 866.5600, Product Code NOE)

CALIBRATOR, SECONDARY (21 CFR 862.1150, Product Code JIT)

LIPOPROTEIN, LOW-DENSITY, ANTIGEN, ANTISERUM, CONTROL (21 CFR 866.5600, Product Code DFC)

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Legally Marketed Device to which Equivalency is Claimed

PLAC® Test (K062234)

Description of Device

The diaDexus PLAC® Test assay consists of separately packaged reagents, calibrators and controls for the measurement of Lp-PLA2 in serum or plasma on automated clinical chemistry analyzers.

PLAC® Test Reagent Kit .
- R1 Tris-based buffer solution
- R2 Suspension of latex microparticles coated with mouse monoclonal antibodies specific to Lp-PLA2 (2C10 and 4B4).
PLAC® Test Calibrator Kit .

Five level set of Lp-PLA2 calibrators made with recombinant Lp-PLA2 in a protein stabilizing buffer and used to calibrate the PLAC assay.

Lp-PLA2 Control Kit .
Two level set of Lp-PLA2 controls made with recombinant Lp-PLA2 in a protein stabilizing buffer and used for quality control of the PLAC assay.

Characterization of Rare Reagents

Antigen

The antigen used in the diaDexus turbidimetric immunoassay PLAC® Test is purified recombinant Lp-PLA2 (DDX-RA). Antigen preparations were characterized using SDSpolyacrylamide 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 (2C10 and 4B4) used in the preparation of the coated microparticles were characterized for purity and reactivity in a series of procedures including Paragon gel electrophoresis, SDS-PAGE, size exclusion

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chromatography, isotyping and enzyme immunoassay. These results demonstrated that the monoclonal antibodies bind to the Lp-PLA2 antigen quantitatively and specifically.

Intended Use Statements

REAGENT KIT

CALIBRATOR KIT

The PLAC® Test Calibrator Kit is intended to establish points of reference that are used in the determination of values in the measurement of Lp-PLA2 by the PLAC® Test Reagent Kit.

CONTROL KIT

Comparison of Technological Characteristics

The chart below describes the similarities and differences between the device and the predicate, PLAC® Test ELISA kit.

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	PredicatePLAC® TestK062234	Device
Intended Use	REAGENT KITThe diaDexus PLAC® Test is anenzyme immunoassay for thequantitative determination of Lp-PLA2(lipoprotein-associated phospholipaseA2) in human plasma and serum, to beused in conjunction with clinicalevaluation and patient risk assessmentas an aid in predicting risk for coronaryheart disease, and ischemic strokeassociated with atherosclerosis.(Calibrators included in kit.)	REAGENT KITThe PLAC® Test Reagent Kit is aturbidimetric immunoassay for thequantitative determination of Lp-PLA2(lipoprotein-associated phospholipase A2) inhuman plasma or serum on automatedclinical chemistry analyzers, to be used inconjunction with clinical evaluation andpatient risk assessment as an aid inpredicting risk for coronary heart disease,and ischemic stroke associated withatherosclerosis.CALIBRATOR KITThe PLAC® Test Calibrator Kit is intendedto establish points of reference that are usedin the determination of values in themeasurement of Lp-PLA2 by the PLAC®Test Reagent Kit.
Intended Use	CONTROL KITThe Lp-PLA2 Controls are intended foruse with the diaDexus PLAC® Test, anenzyme immunoassay for thequantitative determination of Lp-PLA2in human plasma and serum. The Lp-PLA2 Controls are intended as aQuality Control tool to monitor Lp-PLA2 clinical laboratory results. Twolevels of Controls are provided tomonitor the performance within theclinical range of the assay.	CONTROL KITThe Lp-PLA2 Control Kit is intended for useas a quality control tool to monitor theperformance within the clinical range of thePLAC® Test Reagent Kit, a turbidimetricimmunoassay for the quantitativedetermination of Lp-PLA2.
Methodology	Microplate Enzyme immunoassay(ELISA)	Latex particle-enhanced turbidimetricimmunoassay (particle agglutination)
DetectionMethod	Microplate spectrophotometer read at450 nm	Automated clinical chemistry analyzersread at 570 nm
AnalyteSample	Lp-PLA2Serum, EDTA-plasma, heparin-plasma	SameSame
ReagentComponents	Dual monoclonal antibody sandwichELISA:• anti-Lp-PLA2 mAb (2C10) coatedstripwells• Wash Buffer• Enzyme Conjugate : anti-Lp-PLA2 mAb (4B4)-HRP• TMB Substrate Solution• Stop Solution	Two-reagent system:• R1: Tris-based buffer solution• R2: Suspension of anti-Lp-PLA2(mAbs 2C10 and 4B4) coated latexbeads
	PredicatePLAC® TestK062234	Device
Calibration	Six calibrators made with recombinantLp-PLA₂ in a buffered protein matrix(included in ELISA kit)	Five calibrators made with recombinantLp-PLA₂ in a buffered protein matrix (soldseparately)
CalibrationLevels	0, 50, 100, 250, 500, 1000 ng/mL	0, 50, 100, 250, 500 ng/mL
QualityControl	• 2 levels• Recombinant Lp-PLA₂ in abuffered protein matrix	Same
Risk toPatients	Minimal risk	Same
LaboratoryEnvironment	Professional laboratory	Same

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Performance Characteristics - Analytical

Sensitivity

The minimum detection limit is 4.0 ng/mL, as calculated by interpolation of the mean plus two standard deviations of 20 replicates of the 0 ng/mL Lp-PLA2 calibrator from the standard curve.

Precision

Intra-assay precision (n=80) ranged from 1.6 %CV to 2.4 %CV throughout assay range (69 to 450 ng/mL).

Total precision (n=80) ranged from 1.8 %CV to 3.2 %CV throughout assay range (69 to 450 ng/mL).

Linearity/Assay Range

The average recovery in linearity experiments was 97%, demonstrating linearity of samples over a range of 96 to 472 ng/mL Lp-PLA2.

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Interfering Substances

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

. Bilirubin 20 mg/dL
500 mg/dL Cholesterol ●
Hemoglobin 10,000 mg/dL .
. Triglycerides 3000 mg/dL
Total Albumin* ~6500 mg/dL .
- 2.5 g/dL albumin added to plasma pool of presumptively 4 g/dL albumin

Method Comparison

The turbidimetric immunoassay PLAC Test compared to the cleared PLAC Test (ELISA method) in a correlation study, and analyzed by linear regression, resulted in a correlation coefficient of r = 0.95, with a slope of 1.02.

Performance Characteristics - Clinical

No new clinical data were generated.

Conclusions

The latex-particle enhanced turbidimetric immunoassay PLAC Test has the same performance characteristics and clinical utility as the cleared enzyme immunoassay PLAC Test (K062234), and therefore is substantially equivalent.

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DEPARTMENT OF HEALTH & HUMAN SERVICES

Image /page/6/Picture/1 description: The image shows the logo for the Department of Health & Human Services - USA. The logo is a circular seal with the words "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" around the perimeter. Inside the circle is an abstract image of an eagle.

Public Health Service

Food and Drug Administration 2098 Gaither Road Rockville MD 20850

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

DEC 2 0 2007

K072599 Re:

Trade/Device Name: PLAC® Test Reagent Kit PLAC® Test Calibrator Kit Lp-PLA2 Control Kit

Regulation Number: 21 CFR 866.5600 Regulation Name: Low-density lipoprotein immunological test system Regulatory Class: Class II Product Code: NOE, JIT, JJX Dated: December 11, 2007 Received: December 12, 2007

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).

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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) 276-0490. 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 (240) 276-3150 or at its Internet address at http://www.fda.gov/cdrh/industry/support/index.html.

Sincerely yours,

Jean M. Cooper, M.S., D.V.M.

Jean M. Cooper, M.S., D.V.M. 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 (if known):

Device Name: PLAC® Test Reagent Kit PLAC® Test Calibrator Kit Lp-PLA2 Control Kit

Indication For Use:

The PLAC® Test Calibrator Kit is intended to establish points of reference that are used in the determination of values in the measurement of Lp-PLA2 by the PLAC® Test Reagent Kit.

Prescription Use X (21 CFR Part 801 Subpart D) And/Or

Over the Counter Use (21 CFR Part 801 Subpart C)

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

Concurrence of CDRH, Office of In Vitro Diagnostic Device Evaluation and Safety (OIVD)

Carol C. Benson

Division Sign-Off Office of In Vitro Diagnostic Device Evaluation and Safety

510(k) K072599

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).