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The VITEK®DENSICHEK® instrument is an accessory intended for use with the VITEK® 2 Systems to measure the optical density of a microorganism suspension. The instrument provides values in McFarland units, proportional to the microorganism concentration. VITEK® is intended for use with polystyrene tubes, and the reading range is 0.00 to 4.00 McFarland. The VITEK® DENSICHEK® has applications as an in vitro diagnostic medical device, or in an industry setting.

The VITEK® DENSICHEK® consists of the following accessories and components:

• . VITEK® DENSICHEK® Pod
• VITEK® DENSICHEK® Display Base ●
• VITEK® DENSICHEK® Connectivity Base ●
• . VITEK® DENSICHEK® McFarland Reference Kit
• USB Power Adaptor .

The VITEK® DENSICHEK® is an optical reading device intended for professional use by laboratory health professionals in clinical or industry laboratory settings. The device determines the McFarland value by evaluating the absorption of light in the test tube containing the suspension. The more turbid the organism suspension is, the higher the McFarland value displayed by the device. An algorithm assesses results obtained from the turbidimetric reading and translates them into a McFarland value.

The VITEK® DENSICHEK® instrument contains a Base unit with a detachable optical interface, the Pod. The Pod calculates and automatically transmits the optical McFarland reading to the Base unit for display. The user can confirm the McFarland value by pressing a button on the Pod, optionally saving the value to the VITEK® FLEXPREP™ Software on a laboratory PC, where it is recorded with specimen setup information for traceability.

The Pod McFarland readings are communicated to the Base through a Bluetooth Low Energy (BTLE) wireless interface. When docked on a Base, the Pod is automatically paired and recharged through a wireless contact connection. The Display Base displays McFarland readings from the Pod on an LCD resistive touch screen, and can be integrated with VITEK® 2 software to record readings for traceability. The Connectivity Base is available for customers who only want to use the VITEK® DENSICHEK® with the VITEK® 2 software to display and record McFarland readings. McFarland Reference Standards featuring radio-frequency identification (RFID) tags are used to verify the measurement accuracy performance of the VITEK® DENSICHEK®.

The provided text from the FDA 510(k) summary for VITEK® DENSICHEK® does not contain information typically found in an AI/ML device submission, such as a ground truth established by experts, MRMC studies, or training/test set details in the context of deep learning models. This document describes a medical device used to measure optical density for microbial suspensions, which is a physical measurement device, not an AI/ML algorithm. Therefore, many of the requested fields are not applicable in this context.

Based on the provided text, here's an analysis of the acceptance criteria and study data:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for reproducibility studies typically involve a certain percentage of agreement or reproducibility rate. While explicit numerical acceptance criteria are not tabulated, the text indicates the performance was "acceptable" based on established norms for this type of device.

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

The text refers to "isolates tested" and "strain / antimicrobial combination" but does not explicitly state the total number of unique samples (e.g., number of microbial suspensions tested) for each study.

• Study 1: "isolates tested with Gram-negative, Gram-positive, Streptococus, and Yeast AST card types." No specific sample size provided. Provenance likely clinical setting given the description.
• Study 2:
  • Distribution of Dilution Differences:
    • Auto: 190 strain/antimicrobial combinations
    • Manual: 190 strain/antimicrobial combinations
    • Combined: 380 strain/antimicrobial combinations
  • Reproducibility Rates: The numbers derive from the same underlying data as the dilution differences.
  • Data Provenance: Not explicitly stated, but implied to be from internal testing ("comparison of modes between the two product builds").
• Study 3:
  • Distribution of Dilution Differences & Reproducibility Rates:
    • Auto: 190 strain/antimicrobial combinations
    • Manual: 190 strain/antimicrobial combinations
    • Combined: 380 strain/antimicrobial combinations
  • Data Provenance: "A subset of the reproducibility data collected internally using VITEK® Product Build 2 was combined with data collected at two external sites." This indicates a combination of internal and external prospective clinical data from multiple sites. Country of origin not specified.

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

Not applicable. This device measures optical density. The "ground truth" for optical density measurements would be established by physical standards and calibrations, not by human expert interpretation in the way it is for image-based diagnostic AI.

4. Adjudication method for the test set

Not applicable. This is not an interpretive device requiring human adjudication of results.

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 device is not an AI/ML algorithm that assists human readers. It is a measurement instrument.

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

This refers to the core function of the device, which is an automated measurement of optical density. Its performance is evaluated as a standalone instrument. The data provided in the tables (e.g., dilution differences, reproducibility rates) represent the performance of the device itself (VITEK® DENSICHEK®) and its comparison to a predicate device (DensiCHEK® Plus) or different product builds, not a human-in-the-loop scenario.

7. The type of ground truth used

The "ground truth" in this context is the actual (or reference) McFarland values and the expected behavior/reproducibility of the optical density measurements. This would be established through:

• Reference Standards: The document mentions "McFarland Reference Standards" used to verify measurement accuracy. These are likely chemically or physically calibrated standards.
• Comparisons to Predicate Devices: The DensiCHEK® Plus serves as a comparative "ground truth" or reference for equivalency, implying its established performance is the benchmark.
• Reproducibility: The consistency of the device's own measurements across repeated tests provides the "ground truth" for its reproducibility.

It is not based on expert consensus, pathology, or outcomes data in the traditional sense of diagnostic imaging or clinical trials for disease states.

8. The sample size for the training set

Not applicable in the context of AI/ML training data. This device is a physical instrument, not an AI/ML model trained on a dataset. Its "training" would involve engineering design, calibration, and validation, not AI model training.

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

Not applicable, as this is not an AI/ML device with a "training set" in that sense.

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