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VITEK® MS 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 is a qualitative in vitro diagnostic device in conjunction with other clinical and laboratory findings to aid in the diagnosis of bacterial, yeast and mould infections.

VITEK® MS is 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 is a qualitative in vitro diagnostic device indicated for use in coniunction with other clinical and laboratory findings to aid in the diagnosis of bacterial, yeast and mould infections.

The VITEK® MS is intended for laboratory use by professional users who are trained in microbiology and good laboratory practices.

This 510(k) is an update to the VITEK® MS (Mass Spectrometry) clinical knowledge base (KB v3.0.0) for the purposes of identifying Mycobacterium, Nocardia, and mould isolates. As the VITEK® MS KB v3.0.0 update includes new indications for use on the VITEK® MS system, new clinical data was required to establish safety and effectiveness. To account for the detection of higher mass peaks, relevant for some moulds and Mycobacterium, the VITEK® MS acquisition station software was optimized (in v1.5.0) .

Microorqanism identifications are are made 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. Depending on the isolate culture, the analyte sample 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 spotted to the target slide, a matrix is added for the purpose of easy sublimation and strong absorbance in the laser wavelength employed by the instrument.

The slide is then loaded onto the 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. The ionized molecules are then accelerated in an electromagnetic field and a grid electrode in the ionization chamber. 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.

The time of flight 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 mass spectrum displays results as a series of peaks (spectrum) which correspond to the ionized proteins derived from the analyte sample. The mass spectra are sufficiently distinctive to allow taxonomic characterization at the genus and species.

The VITEK® MS system 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. It is a qualitative in vitro diagnostic device used in conjunction with other clinical and laboratory findings to aid in the diagnosis of bacterial, yeast, and mold infections. This summary specifically details the performance of the VITEK® MS with an updated clinical knowledge base (KB v3.0.0) for identifying Mycobacterium, Nocardia, and mold isolates.

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the VITEK® MS updated with KB v3.0.0 are implied by the reported performance, aiming for high agreement rates and very low error rates when compared against a reference method (molecular sequencing).

Reported Device Performance for Challenge Strains (Mycobacterium, Nocardia, and Mold Combined):

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

• Sample Size (Clinical Strains): A total of 2,695 isolates (Mycobacterium, Nocardia, and mold) were tested.
• Sample Size (Challenge Strains): 100 well-characterized challenge strains were included (50 molds, 35 Mycobacterium, and 15 Nocardia).
• Data Provenance: The study was conducted at five clinical sites. The document does not specify the country of origin of the data, but it is implied to be clinical data from human specimens. The data is prospective in the sense that it was collected specifically for this performance testing, but the isolates themselves would have been collected as part of routine clinical practice.

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

The document does not specify the number or qualifications of experts used to establish the ground truth beyond stating that the reference method was "molecular sequencing methods." This suggests that the ground truth was established through laboratory testing rather than human expert consensus on morphological characteristics, for example.

4. Adjudication Method for the Test Set

The document does not explicitly state an adjudication method. The performance evaluation was a direct comparison of the VITEK MS identification results to molecular sequencing methods.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This device identifies microorganisms and does not involve human readers interpreting images or data directly in a way that an MRMC study would typically assess. The performance is assessed on the accuracy of the device's identification against a reference standard.

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

Yes, the performance study described is a standalone performance assessment of the VITEK® MS system. The device automatically generates an identification based on MALDI-TOF MS data, and its results are compared directly to a molecular sequencing reference method. While professional users trained in microbiology operate the device and interpret its output in a laboratory setting, the core performance reported (agreement, error, no-ID rates) reflects the algorithm's capability without direct human interpretation influencing the primary identification result itself.

7. The Type of Ground Truth Used

The ground truth used was molecular sequencing methods. This is considered a highly accurate and definitive method for identifying microorganisms at the species level. Clinical strains included samples from both solid and liquid culture media.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size for the training set. It refers to the "VITEK® MS clinical knowledge base (KB v3.0.0)," implying a database of known mass spectra used for identification. The development of this knowledge base would have involved a large and diverse collection of characterized organisms, but the specific numbers for the training set are not provided in this summary.

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

The document does not explicitly detail how the ground truth for the training set (clinical knowledge base) was established. However, for such diagnostic platforms, the ground truth for training data is typically established through a combination of:

• Reference methods: Including molecular sequencing (e.g., 16S rRNA gene sequencing for bacteria, ITS sequencing for fungi), conventional biochemical tests, and expert microbiological characterization.
• Pure, well-characterized strains: Often sourced from culture collections (e.g., ATCC).
• Clinical isolates: Confirmed by multiple reliable methods.

The knowledge base would be built by acquiring mass spectral profiles from these ground-truthed organisms.

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