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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.

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.

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:

• 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.

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

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This is a 510(k) premarket notification for an in vitro diagnostic device, the diaDexus PLAC™ test, which is an enzyme immunoassay. The information provided in the document focuses on the regulatory aspects of the device's clearance and does not contain the details requested about acceptance criteria, study methodologies, sample sizes, ground truth establishment, or expert involvement for a clinical study proving device performance.

The document states that the FDA has determined the device is "substantially equivalent" to legally marketed predicate devices. This determination typically relies on demonstrating that the new device has the same intended use and technological characteristics as a predicate device, or if there are differences, that those differences do not raise new questions of safety and effectiveness.

Therefore, I cannot provide the requested information based on the provided text. The document is a regulatory clearance letter, not a clinical study report.

Ask a specific question about this device