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VITEK® MS PRIME is a mass spectrometry system using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) for the identification of microorganisms cultured from human specimens.

The VITEK® MS PRIME system is a qualitative in vitro diagnostic device indicated for use in conjunction with other clinical and laboratory findings to aid in the diagnosis of bacterial and fungal infections.

This 510(k) submission introduces the VITEK®MS PRIME System. The VITEK® MS PRIME is intended for laboratory use by professional users who are trained in microbiology and good laboratory practices.

The VITEK® MS PRIME makes microorganism identifications via matrix-assisted laser desorption/ionization - time of flight mass spectrometry (MALDI-TOF MS) technology, which includes the three basic principles of ionization, separation, and detection,

As a first step, a VITEK® MS-DS Target Slide is prepared in accordance with the instructions for use.

NOTE: Depending on the culture, the analyte sample (i.e. microorganism from cultured media) may be directly spotted to a target slide, or for Mycobacterium. Nocardia and mould it must be processed/inactivated before adding to the target slide.

Once the specimen (cultured from the appropriate media) is spotted to the target slide, a matrix is added for the purpose of easy sublimation and strong absorbance in the laser wavelength employed by theinstrument.

NOTE: The VITEK® MS PRIME is a Class 1 laser product, containing a Class 4 Neodymium-doped yttrium lithium fluoride (Nd:YLF) laser – the laser operates at a wavelength of 349 nm.

The prepared slide is then loaded onto the VITEK®MS PRIME instrument. where a laser targets the sample spot and pulses the isolate spot, resulting in vibrational excitation of matrix and analyte molecules. The matrix transfer protons to the analyte resulting in a positive charge. So as part of the first basic principle, the ionized molecules are then accelerated in an electromagnetic field and a grid electrode in the ionization chamber.

The acceleration in the electromagnetic field is the beginning of the second basic principle (i.e. the separation process that is based of the time-of-flight principle). The velocity of the molecules depends on the mass-to-charge (m/z) ratio of the analyte, with heavier molecules having a higher moment of inertia resulting in a lower velocity.

As a final step in the basic principle of MALDI-ToF technology (i.e. detection) the time of flight is measured precisely by the ions arrival at a particle detector. This speed of the ions in flight depends on their mass - with heavier molecules having a higher moment of inertia resulting in a lower velocity. The time of transit is measured precisely by the ions' arrival at a particle detector. Based on the time of flight, the m/z ratio of each particle can be determined, and a mass spectrum of the analyte sample mixture is generated. The recorded signal is processed and presented as a spectrum of intensity versus mass in Daltons (Da). The mass spectrum displays results as a series of peaks (spectrum) which correspond to the ionized proteins derived from the analyte sample. And for identification of an unknown organism, the resulting mass spectra are sufficiently distinctive to allow taxonomic characterization at the genus and species when compared against the VITEK® MS Knowledge Base.

Here's a breakdown of the acceptance criteria and study information for the VITEK® MS PRIME, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance:

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

• Biological Equivalency Study:

  • Sample Size: 1461 samples (representing 487 unique tests in triplicate).
  • Data Provenance: Not explicitly stated, but the strains tested included "critical pathogens" for the 479 claimed species. It is likely a combination of well-characterized laboratory strains and potentially some clinical isolates, given the reference to "clinically validated isolates." retrospective or prospective is not mentioned.

• Clinical Performance Evaluation:

  • Sample Size: 500 clinical isolates (from 100 species with five strains each).
  • Data Provenance: "clinical isolates tested from all sites combined." The specific countries of origin are not specified, but the data is explicitly from "clinical isolates," suggesting data from human specimens. The study design of using "clinical isolates" usually implies retrospective or prospectively collected samples from clinical settings. It refers to "reference identification obtained during previous clinical studies," suggesting a retrospective use of previously characterized clinical data.

• Challenge Isolate Results:

  • Sample Size: 100 challenge strains.
  • Data Provenance: Not specified, but "challenge strains" often refers to a curated set of difficult-to-identify or representative strains used for rigorous testing.

• Quality Control Results:

  • Sample Size: Not explicitly stated, but refers to "all quality control strains tested at all sites."

• Reproducibility Results:

  • Sample Size: Not explicitly stated, but refers to "Reproducibility strains."

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

• The document does not directly state the number of experts or their qualifications.
• For the Clinical Performance Evaluation, the ground truth was established by "a one choice or multiple choice (more than one species) reference identification obtained during previous clinical studies." This implies that the reference identifications were well-established and accepted, likely through conventional microbiological methods and expert interpretation from those previous studies. The nature of these "previous clinical studies" (e.g., whether they involved expert consensus or a gold standard method) is not detailed.

4. Adjudication Method for the Test Set:

• The document does not explicitly describe an adjudication method for the test set results. The ground truth for the clinical performance evaluation was "reference identification obtained during previous clinical studies," implying that disagreements with a single reference standard were likely noted as discordant results rather than undergoing a separate adjudication process within this specific study.

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

• No MRMC comparative effectiveness study is mentioned. This device (VITEK® MS PRIME) is an automated system for microorganism identification using MALDI-TOF MS technology, which does not involve human readers interpreting results in the same way an imaging AI algorithm would. Its performance is compared to a reference method, not to human readers' performance with and without AI assistance.

6. Standalone Performance:

• Yes, a standalone performance study was done. Both the "Biological Equivalency study" and "Clinical Performance Evaluation" describe the performance of the VITEK® MS PRIME system alone (algorithm only) in identifying microorganisms, comparing its results to a ground truth or reference identification. The stated agreement rates (e.g., 98.4% clinical agreement) are measures of this standalone performance. The device is described as "a qualitative in vitro diagnostic device indicated for use in conjunction with other clinical and laboratory findings," but the performance metrics provided are for the device's identification capability itself.

7. Type of Ground Truth Used:

• The ground truth used appears to be reference identification by accepted microbiological methods (which implicitly includes expert consensus in their establishment).
  • For the Biological Equivalency study, performance was measured "in comparison with the reference method."
  • For the Clinical Performance Evaluation, performance was determined by comparing the VITEK® MS PRIME identification to "a one choice or multiple choice (more than one species) reference identification obtained during previous clinical studies." This "reference identification" would be established through a combination of traditional culture-based methods, molecular methods, and expert interpretation/consensus over time, serving as the gold standard for organism identification. "Outcomes data" or "pathology" as the direct ground truth are not mentioned for identifying the microorganisms themselves, though the device aids in diagnosis of infections.

8. Sample Size for the Training Set:

• The document does not explicitly state the sample size for the training set. It refers to a "VITEK® MS Knowledge Base" (KB v3.2) against which the mass spectra are compared. This knowledge base is the "training set" or reference library. The complexity and size of this knowledge base are not detailed in terms of number of samples/isolates used to build it.

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

• The document states that identifications are made "when compared against the VITEK® MS Knowledge Base." While it doesn't describe the exact process for building this KB, such knowledge bases for MALDI-TOF MS systems are typically built by:
  • Acquisition of mass spectra from a large collection of well-characterized and phenotypically/genetically confirmed (often by sequencing, biochemical tests, or other gold-standard methods) reference strains across various species.
  • Each reference strain's identity is verified by expert microbiologists using established methods before being added to the database.
  • The collection process ensures reproducibility and representation of intra-species variability.
  • Thus, the ground truth for the training set (Knowledge Base) is established through a rigorous process of expert-validated identification using traditional and molecular microbiological gold standards.

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