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The DensiCHEK™ Plus instrument is intended for use with the VITEK® and VITEK® 2 Systems to measure the optical density of a microorganism suspension. The instrument provides values in McFarland units, proportional to microorganism concentrations. DensiCHEK Plus is indicated for use with polystyrene and glass test tubes and the reading range is 0.0 - 4.0 McFarland. The DensiChek™ Plus has applications as an in vitro diagnostic device.

DensiCHEK™ Plus is intended for use with the VITEK® and VITEK® 2 Systems to measure the optical density of a microorganism suspension. The instrument provides values in McFarland units, proportional to microorganism concentrations. The DensiCHEK Plus has applications as an in vitro diagnostic medical device. The DensiCHEK Plus generates a McFarrand value using basic colorimetry, which is a method of measurement that relates the amount of color in a transparent medium (liquid) to the amount of a particular substance in the liquid. The DensiCHEK Plus measures the turbidity of the saline and microorganism suspension using a single wavelength, 580 nm. The absorption of light determines the McFarland value generated by the instrument. The light source in the DensiCHEK plus is an LED that emits a narrow range of wavelengths, and an interference filter is used between the LED and the test tube (sample) to further narrow the wavelength to 580 nm. There are 2 calibration curves pre-programmed into the DensiCHEK Plus, one for glass tubes and one for plastic tubes.

Here's a summary of the acceptance criteria and study information for the DensiCHEK™ Plus as found in the provided document:

The document explicitly states that the DensiCHEK™ Plus demonstrated acceptable accuracy, repeatability (within instrument variability), and reproducibility (between instrument variability) during validation. However, it does not provide a specific table of acceptance criteria or the reported device performance values for these metrics. It only broadly claims "acceptable" performance.

Regarding the predicate device comparison, it states: "DensiCHEK Plus demonstrated substantially equivalent performance when compared with the DensiChek in the performance equivalency study utilizing VITEK 2 Identification and Susceptibility cards and systems." Again, specific numerical results of this equivalency are not provided.

Given the limitations of the provided text, many of the requested details about the study are not available.

1. Table of Acceptance Criteria and Reported Device Performance

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

• Sample Size: Not specified.
• Data Provenance: Not specified (e.g., country of origin, retrospective/prospective).

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

• This information is not provided. The device measures optical density (McFarland units) and does not inherently rely on expert ground truth in the way a diagnostic imaging device might. Its "ground truth" would likely be based on established physical standards or comparative measurements to a calibrated reference.

4. Adjudication Method for the Test Set

• Not applicable/Not specified as the test doesn't involve subjective interpretation that would require adjudication.

5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study

• No, an MRMC study was not done, or at least not described in this document. This type of study is typically relevant for diagnostic devices where human readers interpret output (e.g., medical images). The DensiCHEK Plus is an instrument that provides a direct numerical measurement (McFarland value).

6. Standalone (Algorithm Only) Performance Study

• Yes, this entire submission describes the standalone performance of the DensiCHEK Plus. While it mentions use with VITEK and VITEK 2 Systems, the performance validation discussed ("accuracy, repeatability, reproducibility") refers to the DensiCHEK Plus instrument itself and its ability to measure optical density.

7. Type of Ground Truth Used

• The ground truth for the DensiCHEK Plus's measurements (McFarland values) would be based on physical standards or calibrated reference methods. The device generates a McFarland value using "basic colorimetry" and compares the absorption of light at 580 nm. The ground truth for this would be the actual, chemically or physically determined turbidity/concentration of microorganism suspensions, or highly accurate reference turbidimeters. The document does not explicitly state how this ground truth was established, but it would involve known standards.

8. Sample Size for the Training Set

• Not specified. The document does mention "2 calibration curves pre-programmed into the DensiCHEK Plus, one for glass tubes and one for plastic tubes," implying some form of internal calibration and potentially "training" specific to these tube types, but details are absent.

9. How the Ground Truth for the Training Set Was Established

• Not explicitly described. For a device like this, the "ground truth" for calibration curves would be established by precisely measuring known concentrations of microbial suspensions (or turbidity standards simulating them) across the specified range, using a highly accurate reference method. This data would then be used to create the specific calibration curves for glass and plastic tubes that equate measured absorbance to McFarland units.

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