(260 days)
The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System is an in vitro diagnostic product for clinical susceptibility testing of non-fastidious isolates.
This 510(k) is for vancomycin in the dilution range of 0.25-128 ug/mL for testing non-fastidious gram-positive isolates on the Sensititre 18-24 hour MIC or Breakpoint Susceptibility System. Testing is indicated for Staphylococcus aureus, Staphylococci other than Staphylococcus aureus, and Enterococcus spp., as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.
The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin in the dilution range of 0.25-128 ug/mL demonstrated acceptable performance with the following organisms:
Staphylococcus aureus (including MRSA)
Staphylococci other than Staphylococcus aureus (S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, S. saprophyticus)
Enterococcus spp. (E. faecalis, E. faecium)
Not Found
The provided FDA 510(k) clearance letter pertains to an Antimicrobial Susceptibility Test (AST) System (The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin). This type of medical device is designed to determine the susceptibility of bacteria to various antimicrobial agents.
It's crucial to understand that the information typically requested in your prompt (especially regarding AI/ML models, MRMC studies, expert consensus on ground truth for medical images, etc.) is NOT APPLICABLE to this type of device. The FDA clearance letter describes a traditional in vitro diagnostic product, not a software-as-a-medical-device (SaMD) or an AI/ML-powered diagnostic aid.
Therefore, the following points address the questions to the extent they are relevant to a traditional AST system, while clarifying where the requested information is not applicable.
Description of Acceptance Criteria and Study Proving Device Performance for The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin
This device is an in vitro diagnostic product used for clinical susceptibility testing of non-fastidious bacterial isolates against Vancomycin. The performance of such systems is typically evaluated based on their ability to accurately determine the Minimum Inhibitory Concentration (MIC) or breakpoint susceptibility, which is compared to a reference method.
1. Table of Acceptance Criteria and Reported Device Performance
For Antimicrobial Susceptibility Test (AST) systems, acceptance criteria are generally based on agreement rates with a reference method (e.g., broth microdilution or agar dilution as per CLSI standards). The key performance metrics are:
- Essential Agreement (EA): The MIC result obtained by the test device is within ±1 doubling dilution of the reference method MIC.
- Categorical Agreement (CA): The interpretation (Susceptible, Intermediate, Resistant) obtained by the test device agrees with the interpretation from the reference method.
- Minor Errors (mE): The test device classifies a sample as Susceptible when the reference method classifies it as Intermediate or Resistant, or as Intermediate when the reference method classifies it as Susceptible or Resistant.
- Major Errors (ME): The test device classifies a sample as Resistant when the reference method classifies it as Susceptible.
- Very Major Errors (VME): The test device classifies a sample as Susceptible when the reference method classifies it as Resistant.
Typical Acceptance Criteria (General for AST, specific values are submission-dependent):
| Performance Metric | Acceptance Criteria (General) | Reported Device Performance (Not explicitly stated in the letter, but implied for clearance) |
|---|---|---|
| Essential Agreement (EA) | ≥ 90-95% (e.g., typically ≥ 90% for clinical isolates) | Implied to be met for clearance |
| Categorical Agreement (CA) | ≥ 90-95% (e.g., typically ≥ 90% for clinical isolates) | Implied to be met for clearance |
| Minor Errors (mE) | ≤ 10% | Implied to be within acceptable limits |
| Major Errors (ME) | ≤ 3% | Implied to be within acceptable limits |
| Very Major Errors (VME) | ≤ 1.5% (especially for critical drugs like Vancomycin) | Implied to be within acceptable limits |
The clearance letter states: "The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin in the dilution range of 0.25-128 µg/mL demonstrated acceptable performance with the following organisms: Staphylococcus aureus (including MRSA), Staphylococci other than Staphylococcus aureus (S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, S. saprophyticus), Enterococcus spp. (E. faecalis, E. faecium)." This statement confirms that the specific performance criteria (EA, CA, mE, ME, VME) were met for these organisms, although the exact percentages are not provided in the public clearance letter.
2. Sample Size Used for the Test Set and Data Provenance
The clearance letter does not specify the exact sample size used for the test set. For AST systems, the test set typically includes a significant number of clinical isolates (hundreds to thousands, often including challenge strains with known resistance mechanisms) to ensure robustness across various resistance profiles.
- Data Provenance: For in vitro diagnostic devices, data is typically collected from prospective and/or retrospective clinical samples from laboratories, often from multiple geographically diverse sites within the country of submission (e.g., the United States for FDA clearance) to represent real-world clinical populations. Some isolates may also come from culture collections.
3. Number of Experts Used to Establish Ground Truth and Qualifications
This question is not applicable in the context of an AST system being cleared.
- Ground truth for AST systems is established by validated reference methods (e.g., CLSI broth microdilution, agar dilution, or molecular methods for specific resistance genes) run by trained laboratory personnel, not by expert interpretation of images or clinical data. There are no "experts" in the sense of physicians or radiologists reviewing and labeling data.
4. Adjudication Method for the Test Set
This question is not applicable.
- Since ground truth is established by a quantitative laboratory method, there is no "adjudication" in the sense of multiple human readers resolving disagreements. Discrepancies between the test device and the reference method would be analyzed, and repeated testing or further characterization of the isolate might occur if needed during the study design, but it's not a consensus-based adjudication process.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, and its effect size
This question is not applicable.
- MRMC studies are relevant for devices that involve human interpretation of medical images or complex data (e.g., AI-powered CADe/CADx devices for radiology). An AST system is an automated or semi-automated laboratory instrument that provides a direct result (MIC value, interpretation) based on bacterial growth or lack thereof. There is no "human reader" component in the direct output of the device that would be assisted by AI, nor is there a direct human comparative effectiveness study for its primary function.
6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was done
This question is not applicable in the sense of an AI algorithm.
- The Sensititre 18-24 hour system is primarily a "standalone" device in that it produces susceptibility results without requiring human "interpretation" of a complex output like an image. Its performance is evaluated independently against a reference method. However, it's not an "algorithm only" in the sense of a software-driven AI solution; it is a laboratory instrument that performs a specific biological assay.
7. The Type of Ground Truth Used
- The ground truth for AST systems is based on reference antimicrobial susceptibility testing methods, typically broth microdilution or agar dilution as per a recognized standard (e.g., Clinical and Laboratory Standards Institute - CLSI guidelines). This is considered the "gold standard" for determining MIC values and categorical interpretations. In some cases, molecular methods (e.g., PCR for resistance genes) might be used to confirm certain resistance mechanisms, which indirectly supports the "ground truth" for specific resistant phenotypes.
8. The Sample Size for the Training Set
This question is not applicable for a traditional AST system.
- Traditional AST systems are not "trained" in the way AI/ML models are. They are designed and validated based on established microbiological principles. There is no distinct "training set" of data used to iteratively improve an algorithm's performance. Instead, the device is developed, and its performance is then validated against a large test set to ensure accuracy and reproducibility.
9. How the Ground Truth for the Training Set was Established
This question is not applicable for a traditional AST system, as there is no "training set" in the AI/ML sense.
In summary, the FDA clearance for The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin is based on the device's ability to accurately determine antimicrobial susceptibility by comparing its results to established reference methods using a statistically significant number of relevant bacterial isolates. The concepts of AI/ML model training, human expert consensus for image interpretation, and MRMC studies are not relevant to the validation of this traditional in vitro diagnostic device.
FDA 510(k) Clearance Letter
Page 1
U.S. Food & Drug Administration
10903 New Hampshire Avenue Doc ID # 04017.07.05
Silver Spring, MD 20993
www.fda.gov
May 22, 2025
Thermo Fisher Scientific
Dylan Staats
Supervisor, R&D, AST and Pharma
1 Thermofisher Way
Oakwood Village, Ohio 44146
Re: K242659
Trade/Device Name: The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin in the dilution range of 0.25-128 µg/mL
Regulation Number: 21 CFR 866.1640
Regulation Name: Antimicrobial Susceptibility Test Powder
Regulatory Class: Class II
Product Code: JWY, LRG, LTT
Dated: April 29, 2025
Received: April 29, 2025
Dear Dylan Staats:
We have reviewed your section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (the Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database available at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
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K242659 - Dylan Staats Page 2
FDA's substantial equivalence determination also included the review and clearance of your Predetermined Change Control Plan (PCCP). Under section 515C(b)(1) of the Act, a new premarket notification is not required for a change to a device cleared under section 510(k) of the Act, if such change is consistent with an established PCCP granted pursuant to section 515C(b)(2) of the Act. Under 21 CFR 807.81(a)(3), a new premarket notification is required if there is a major change or modification in the intended use of a device, or if there is a change or modification in a device that could significantly affect the safety or effectiveness of the device, e.g., a significant change or modification in design, material, chemical composition, energy source, or manufacturing process. Accordingly, if deviations from the established PCCP result in a major change or modification in the intended use of the device, or result in a change or modification in the device that could significantly affect the safety or effectiveness of the device, then a new premarket notification would be required consistent with section 515C(b)(1) of the Act and 21 CFR 807.81(a)(3). Failure to submit such a premarket submission would constitute adulteration and misbranding under sections 501(f)(1)(B) and 502(o) of the Act, respectively.
Additional information about changes that may require a new premarket notification are provided in the FDA guidance documents entitled "Deciding When to Submit a 510(k) for a Change to an Existing Device" (https://www.fda.gov/media/99812/download) and "Deciding When to Submit a 510(k) for a Software Change to an Existing Device" (https://www.fda.gov/media/99785/download).
Your device is also subject to, among other requirements, the Quality System (QS) regulation (21 CFR Part 820), which includes, but is not limited to, 21 CFR 820.30, Design controls; 21 CFR 820.90, Nonconforming product; and 21 CFR 820.100, Corrective and preventive action. Please note that regardless of whether a change requires premarket review, the QS regulation requires device manufacturers to review and approve changes to device design and production (21 CFR 820.30 and 21 CFR 820.70) and document changes and approvals in the device master record (21 CFR 820.181).
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801 and Part 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR Part 803) for devices or postmarketing safety reporting (21 CFR Part 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reporting-combination-products); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR Part 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR Parts 1000-1050.
All medical devices, including Class I and unclassified devices and combination product device constituent parts are required to be in compliance with the final Unique Device Identification System rule ("UDI Rule"). The UDI Rule requires, among other things, that a device bear a unique device identifier (UDI) on its label and package (21 CFR 801.20(a)) unless an exception or alternative applies (21 CFR 801.20(b)) and that the dates on the device label be formatted in accordance with 21 CFR 801.18. The UDI Rule (21 CFR 830.300(a) and 830.320(b)) also requires that certain information be submitted to the Global Unique Device Identification Database (GUDID) (21 CFR Part 830 Subpart E). For additional information on these
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K242659 - Dylan Staats Page 3
requirements, please see the UDI System webpage at https://www.fda.gov/medical-devices/device-advice-comprehensive-regulatory-assistance/unique-device-identification-system-udi-system.
Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-devices/medical-device-safety/medical-device-reporting-mdr-how-report-medical-device-problems.
For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medical-devices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-devices/device-advice-comprehensive-regulatory-assistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).
Sincerely,
Ribhi Shawar -S
Ribhi Shawar, Ph.D. (ABMM)
Branch Chief
General Bacteriology and Antimicrobial Susceptibility Branch
Division of Microbiology Devices
OHT7: Office of In Vitro Diagnostics
Office of Product Evaluation and Quality
Center for Devices and Radiological Health
Enclosure
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FORM FDA 3881 (6/20) Page 1 of 1 PSC Publishing Services (301) 443-6740 EF
DEPARTMENT OF HEALTH AND HUMAN SERVICES
Food and Drug Administration
Indications for Use
Form Approved: OMB No. 0910-0120
Expiration Date: 06/30/2023
See PRA Statement below.
510(k) Number (if known): K242659
Device Name: The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin in the dilution range of 0.25-128 µg/mL
Indications for Use (Describe):
The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System is an in vitro diagnostic product for clinical susceptibility testing of non-fastidious isolates.
This 510(k) is for vancomycin in the dilution range of 0.25-128 µg/mL for testing non-fastidious gram-positive isolates on the Sensititre 18-24 hour MIC or Breakpoint Susceptibility System. Testing is indicated for Staphylococcus aureus, Staphylococci other than Staphylococcus aureus, and Enterococcus spp., as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.
The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Vancomycin in the dilution range of 0.25-128 µg/mL demonstrated acceptable performance with the following organisms:
Staphylococcus aureus (including MRSA)
Staphylococci other than Staphylococcus aureus (S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, S. saprophyticus)
Enterococcus spp. (E. faecalis, E. faecium)
Type of Use (Select one or both, as applicable)
☑ Prescription Use (Part 21 CFR 801 Subpart D) ☐ Over-The-Counter Use (21 CFR 801 Subpart C)
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§ 866.1640 Antimicrobial susceptibility test powder.
(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).