Search Results

chromID™ MRSA agar is a selective and differential chromogenic medium for :

A. The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA), to aid in the prevention and control of MRSA in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromID™ MRSA when used to detect nasal colonization is not intended to diagnose, guide, or monitor therapy for MRSA infections, or provide results of susceptibility to methicillin.

B. The qualitative detection of MRSA from skin structure infections. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Concomitant cultures for skin structure infections are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.

C. The qualitative detection of MRSA from positive blood cultures demonstrating Gram-positive cocci on Gram stain. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Sub-culturing for positive blood cultures are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude, MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.

chromID™ MRSA agar consists of a rich nutritive base combining different peptones. It also contains a chromogenic substrate of a-glucosidase and a combination of several antibiotics, including cefoxitin, which favor the growth of MRSA including heteroresistant strains and the direct detection of MRSA strains by revealing a-glucosidase activity (patent registered), green colonies. The selective mixture of antibiotics inhibits most bacteria not belonging to the genus Staphylococcus, as well as yeasts. The MRSA strains are identified by the presence of green colonies that result from the chromogen incorporated in the medium. The chromogen targets the a-glucosidase activity of S. aureus. The a-glucosidase produced by S. aureus cleaves the chromogenic substrate, which gives a green color to the S. aureus colonies growing on the medium.

The provide text describes the acceptance criteria and study results for chromID™ MRSA agar, a chromogenic medium for the qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA).

Here's an analysis of the provided information:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are implied by the reported performance data for sensitivity and specificity. The device is expected to perform accurately in detecting MRSA from various specimen types.

Note: The provided text primarily focuses on the clinical performance for blood cultures. While analytical studies are mentioned, specific numerical acceptance criteria for those were not explicitly stated beyond achieving "expected results" or specific growth/detection rates.

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

• Clinical Study Sample Size (Blood Culture): 863 positive blood culture specimens (demonstrating Gram-positive cocci) were initially analyzed. 187 cultures were removed due to low prevalence of the target or protocol deviations, resulting in a final evaluated sample size.
• Data Provenance: The study was conducted at four clinical sites. The geographical location of these sites (e.g., country of origin) is not specified. The clinical study is described as having "analyzed" specimens, suggesting a retrospective or prospective observational design where samples were collected and then tested. The phrase "clinical trial" is used, implying a prospective collection for evaluation. The "Analytical Studies" also mention the use of well-characterized strains, which would be laboratory-based rather than from clinical patients.

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

• The text does not explicitly state the number of experts used to establish the ground truth.
• It also does not specify the qualifications of these experts.

4. Adjudication Method for the Test Set

• The text describes a reference method for establishing ground truth, which involves:
  • Growth on Tryptic Soy agar with 5% sheep blood (BAP).
  • Testing of colonies suggestive of Staphylococcus species by Gram stain, catalase, and latex agglutination.
  • Staphylococcus aureus isolates further tested for resistance to Oxacillin by the Cefoxitin Screen test.
  • All Cefoxitin-resistant colonies tested for the presence of the mecA gene by PCR and by VITEK® MS for species confirmation.
• For discordant specimens in the blood culture clinical study, "Two false positives were confirmed as MRSA positive" and "Five false positives that grew green colonies were not identified as MRSA." This implies a form of adjudication or re-evaluation for discordant results, likely by further expert review or follow-up testing, though a formal "2+1" or "3+1" structure isn't explicitly detailed.

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

• No, an MRMC comparative effectiveness study was not done.
• This device (chromID™ MRSA agar) is a culture medium, not an AI-assisted diagnostic tool. Therefore, the concept of "human readers improve with AI vs. without AI assistance" does not apply.

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

• Yes, a standalone performance was done, but it's important to clarify the context. The "device" here is the chromID™ MRSA agar medium itself. The performance evaluation measures the ability of this agar to correctly identify MRSA based on color change, which is then interpreted by a laboratory user (a manual interpretation of the agar plate).
• The clinical performance data for sensitivity and specificity (100.0% and 98.9% respectively for blood cultures) represent the standalone performance of the chromID™ MRSA agar in classifying samples as MRSA positive or negative, compared to the defined reference method.

7. The Type of Ground Truth Used

• The ground truth for the clinical studies was established using a multi-faceted reference method, which includes:
  • Culture on Tryptic Soy agar with 5% sheep blood (BAP).
  • Gram stain, catalase, and latex agglutination for presumptive identification.
  • Oxacillin resistance testing by Cefoxitin Screen test.
  • Molecular testing (PCR for mecA gene) for definitive confirmation of methicillin resistance.
  • Species confirmation by VITEK® MS.
  • This combination represents a robust "expert consensus" or "gold standard" laboratory method, incorporating phenotypic and genotypic characteristics.

8. The Sample Size for the Training Set

• The document does not explicitly mention a "training set" in the context of machine learning or AI development. Since this is a chromogenic culture medium, its development likely involved iterative formulation and testing, rather than a distinct machine learning training set as typically understood.
• The "Analytical Reactivity (Challenge)" and "Cross Reactivity (Analytical Specificity)" studies, using specific well-characterized strains (80 mecA MRSA strains, 5 mecC MRSA strains, and 71 non-MRSA strains), could be seen as part of the developmental testing that helps "train" the understanding of the medium's performance, but not in the AI sense.

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

• As a "training set" for an AI algorithm is not applicable, the question of its ground truth establishment is also not directly applicable in the AI context.
• However, for the analytical studies involving known strains, the ground truth was established by prior characterization of these strains (e.g., they are known mecA MRSA strains, mecC MRSA strains, or specific non-MRSA species), likely through established microbiological and molecular methods.

Ask a specific question about this device

chromID™ MRSA agar is a selective and differential chromogenic medium for :

A. The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA), to aid in the prevention and control of MRSA in healthcare settings.

The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromID™MRSA when used to detect nasal colonization is not intended to diagnose, guide, or monitor therapy for MRSA infections, or provide results of susceptibility to methicillin.

B. The qualitative detection of MRSA from skin structure infections.

chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Concomitant cultures for skin structure infections are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing.

A negative result does not preclude MRSA infection. chromID™MRSA is not intended to monitor treatment for MRSA · infections, or provide results of susceptibility to methicillin.

chromID™ MRSA agar consists of a rich nutritive base combining different peptones. It also contains a chromogenic substrate of α-glucosidase and a combination of several antibiotics (cefoxitin, etc.) that favor the growth and direct detection of MRSA, including hetero-resistant strains, by revealing orglucosidase activity (patent registered) through the appearance of green colonies. The α-glucosidase produced by S. aureus cleaves the chromogenic substrate, which gives a green color to the S. aureus colonies growing on the medium. The MRSA strains are identified by the presence of green colonies that result from the chromogen incorporated in the medium. The selective mixture of antibiotics inhibits most bacteria not belonging to the genus Staphylococcus, as well as yeasts.

Here's an analysis of the acceptance criteria and study findings for the chromID™ MRSA device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria for the clinical study's sensitivity and specificity. However, the reported performance metrics can be considered the demonstrated performance of the device.

Note: The document does not explicitly state numerical "acceptance criteria" for sensitivity and specificity. The reported values are the observed performance. The FDA's substantial equivalence determination implies these values were deemed acceptable.

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

• Test Set Sample Size: 680 specimens (valid for comparison after exclusions)
• Data Provenance: Clinical study data from four geographically diverse clinical sites. This suggests prospective collection within the United States, given it's an FDA submission. The specific country is not explicitly stated beyond "geographically diverse clinical sites" in relation to the US FDA. The nature of the study (collection of specimens for device evaluation) indicates it's prospective.

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

The document does not specify the "number of experts" or their "qualifications" involved in establishing the ground truth. Ground truth was established using standard microbiological laboratory methods (Reference Culture Method) which would be performed by trained laboratory personnel.

4. Adjudication Method for the Test Set

The document describes a clear reference method for ground truth determination, which inherently serves as the "adjudication" (or gold standard). It does not mention a separate, independent adjudication panel or specific method like "2+1" or "3+1" for resolving discrepancies between the new device and the reference method. Discordant results were analyzed and described.

• Reference Culture Method:
  • Specimens enriched in Tryptic Soy broth with 6.5% NaCl (TSB) for 24 hours (negative broths incubated an additional 24 hours).
  • Positive broth cultures subcultured to Tryptic Soy agar with 5% sheep blood (BAP).
  • Colonies suggestive of Staphylococcus species tested by Gram stain, catalase, and latex agglutination.
  • Staphylococcus aureus isolates tested for resistance to oxacillin by the Cefoxitin Screen test (30µg).
  • All oxacillin-resistant colonies by Cefoxitin Screen test were tested for the presence of the mecA gene by PCR and by VITEK® MS for species confirmation.
• Definition of Positive Ground Truth: Recovery of cefoxitin-resistant Staphylococcus aureus from the specimen.
• Definition of Negative Ground Truth: All other results (growth of cefoxitin-susceptible Staphylococcus aureus, growth of other species, or no growth).

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 is a culture medium, and its performance is assessed by direct comparison to a laboratory reference method, not by comparing human reader interpretations with and without AI assistance.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

This is a standalone microbiological culture medium. Its performance (presence/absence of green colonies indicating MRSA) is interpreted directly by laboratory personnel based on the visual result of the culture. There is no separate "algorithm" being evaluated beyond the efficacy of the chromogenic medium itself. The clinical study evaluates this standalone culture medium's ability to detect MRSA compared to a reference lab method.

7. The Type of Ground Truth Used

The ground truth used was a composite reference standard based on:

• Standard microbiological culture methods (TSB enrichment, BAP subculture)
• Phenotypic tests (Gram stain, catalase, latex agglutination, Cefoxitin Screen test for oxacillin resistance)
• Molecular confirmation (mecA gene PCR)
• Species confirmation (VITEK® MS)

This detailed approach combines multiple laboratory techniques to confirm the presence and methicillin-resistance of Staphylococcus aureus.

8. The Sample Size for the Training Set

The document does not mention a "training set" in the context of an algorithm or machine learning. As a diagnostic culture medium, it would have been developed and optimized through in vitro studies and experiments, but the concept of a "training set" for an algorithm's development, distinct from analytical validation, is not applicable here. The analytical performance data (e.g., reactivity, reproducibility, cross-reactivity) serves to demonstrate the medium's inherent characteristics.

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

Not applicable, as there is no "training set" for an algorithm in the traditional sense. The ground truth for the analytical studies (e.g., for determining mecA status for reactivity studies) would have been established using established molecular and phenotypic methods, similar to those used for the clinical ground truth. For instance, the QC organisms were compared to oxacillin MIC and mecA PCR.

Ask a specific question about this device

chromID™ MRSA agar is a selective and differential chromogenic medium for the qualitative detection of nasal colonization by methicillin-resistant S. aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromID™ MRSA agar is not intended to diagnose MRSA infection nor to guide or monitor treatment for infections.

chromID™ MRSA agar is a selective and differential chromogenic medium for the qualitative detection of MRSA from anterior nares swab specimens.

chromID™ MRSA agar consists of a rich nutritive base combining different peptones. It also contains a chromogenic substrate of a-glucosidase and a combination of several antibiotics, which favor the growth of MRSA including hetero-resistant strains. The antibiotics include: cefoxitin (4 mg/l), aztreonam (64 mg/l), and amphotericin B (3 mg/l). The selective mixture of antibiotics inhibits most bacteria not belonging to the genus Staphylococcus, as well as yeasts. The MRSA strains are identified by the presence of green colonies that result from the chromogen incorporated in the medium. The chromogen targets the a-qlucosidase activity of S. aureus. The a-ducosidase produced by S. aureus cleaves the chromogenic substrate, which gives a green color to the S. aureus colonies growing on the medium. This chromogen is identified as "Green a-glucoside" (5-Bromo-4-chloro-3-indoxyl-N-methyl-α-D-glucoside) (patent registered).

1. Table of Acceptance Criteria and Reported Device Performance:

Note: The document states "Clinical studies were performed and demonstrate acceptable performance of chromID™ MRSA," but specific pre-defined acceptance criteria values are not explicitly listed in this excerpt.

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

   • Test Set Sample Size:
     • MRSA positive samples: 321
     • Non-MRSA samples: 938
     • Total samples in clinical performance comparison: 1259 (321 + 938)
   • Data Provenance: Not explicitly stated in the provided text (e.g., country of origin, retrospective or prospective).

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

   • The document implies that "conventional methods including the identification and susceptibility testing" and other specific molecular/phenotypic tests (Latex Agglutination, Cefoxitin Screen, mecA PCR) were used to establish ground truth. However, the exact number of experts involved in analyzing these conventional methods or establishing the final ground truth, nor their specific qualifications, are explicitly mentioned.

4. Adjudication Method for the Test Set:

   • The document does not explicitly describe an adjudication method for conflicting results. The "Performance is based on the number of true positives detected from either medium during the trial (true positives = number of samples positive by TSAB + number of samples that are false negative by TSAB and positive by chromID™ MRSA)" suggests a hierarchical or combined approach to defining true positives, but not a formal expert adjudication process.

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

   • No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study focusing on how much human readers improve with AI vs. without AI assistance was not mentioned. This device is a diagnostic culture medium, not an AI-assisted diagnostic tool for human readers.

6. Standalone Performance Study:

   • Yes, the clinical performance data presented (e.g., "Clinical Performance Compared to Conventional Methods after 24 h Incubation") represents the standalone performance of the chromID™ MRSA agar against established conventional laboratory methods. The device itself (the agar medium) is the 'algorithm' in this context.

7. Type of Ground Truth Used:

   • The ground truth was established using a combination of "conventional methods including the identification and susceptibility testing" for S. aureus, and specific tests like TSAB (Trypticase Soy Agar with 5% Sheep Blood), Latex Agglutination, Cefoxitin Screen, and mecA PCR. This indicates a laboratory-based, microbiology ground truth (culture, susceptibility testing, molecular diagnostics).

8. Sample Size for the Training Set:

   • The document does not provide details on a separate "training set" as this is a traditional diagnostic medium, not a machine learning algorithm that typically requires a distinct training phase with labeled data. The clinical performance data appears to be from the validation/test set.

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

   • As no separate training set is explicitly mentioned or relevant for this type of device (a diagnostic culture medium), there is no information on how its ground truth would have been established.

Ask a specific question about this device