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BD BBL Sensi-Disc Antimicrobial Susceptibility Test (AST) Discs are used in the semi-quantitative agar diffusion test method for in vitro susceptibility testing.

BD BBL Sensi-Disc Cefiderocol Disc 30 uq (FDC-30) can be used to determine susceptibility to Cefiderocol against the following bacteria, as described in the FDA-approved package insert for this antimicrobial agent.

Active in vitro and in Clinical Infections Against:

Complicated Urinary Tract Infections, Including Pyelonephritis Gram-negative Bacteria Escherichia coli Enterobacter cloacae complex Klebsiella pneumoniae Proteus mirabilis Pseudomonas aeruginosa

Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia (HABP/VABP) Gram-negative Bacteria Acinetobacter baumannii complex Escherichia coli Enterobacter cloacae complex Klebsiella pneumoniae Pseudomonas aeruginosa Serratia marcescens

Active in vitro Against:

Citrobacter freundii complex Citrobacter koseri Klebsiella aerogenes Klebsiella oxytoca Morganella morganii Proteus vulgaris Providencia rettgeri

The BD BBL™ Sensi-Disc™ Cefiderocol 30 µg (FDC30) device is a 6 mm disc prepared by impregnating high quality absorbent paper with accurately determined amounts of Cefiderocol. Discs are clearly marked on both sides with the code FDC30. The code designates the agent Cefiderocol (FDC) and the drug content (30 ug).

BD BBL™ Sensi-Disc ™ Antimicrobial Susceptibility Test Discs are furnished in cartridges containing 50 discs each. The last disc in each cartridge is marked "X" and contains the drug as coded. BD BBLTM Sensi-Disc ™ Antimicrobial Susceptibility Test Discs can be dispensed using a BD BBLTM Sensi-Disc TM Dispenser.

Here's a breakdown of the acceptance criteria and the study details for the BD BBL™ Sensi-Disc™ Cefiderocol 30µg (FDC30), as extracted from the provided FDA 510(k) summary:

Acceptance Criteria and Device Performance

The device's performance was evaluated against a comparator FDA-cleared disk (HardyDisk AST Cefiderocol 30μg (FDC30), K193504). The primary criterion was Category Agreement (CA), which means the BD device's interpretation (Susceptible, Intermediate, Resistant) agreed exactly with the comparator's interpretation.

Study Details

1. Sample size used for the test set and the data provenance:

   • Clinical Isolates: 296 isolates (U.S. origin, prospective).
     • 207 Enterobacterales
     • 52 Pseudomonas aeruginosa
     • 37 Acinetobacter baumannii complex
   • Challenge Isolates: 61 isolates (U.S. origin, prospective). These are likely stock cultures or isolates selected to challenge the device, potentially including resistant strains.
     • 49 Enterobacterales
     • 5 Pseudomonas aeruginosa
     • 7 Acinetobacter baumannii complex
   • Total Test Isolates: 357 (Clinical + Challenge combined).

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • The document implies that the ground truth for categorical interpretation (Susceptible/Intermediate/Resistant) was established by comparing the BD BBL Sensi-Disc performance to an FDA cleared disk (HardyDisk AST Cefiderocol 30µg), not directly by human experts interpreting raw data in the context of the comparison study.
   • For the reproducibility study, "three independent readers" visually read the results. Their specific qualifications are not detailed beyond "independent readers."

3. Adjudication method for the test set:

   • For the primary comparison study, the method was a direct comparison to an FDA-cleared predicate device. No explicit "adjudication" between multiple readers for ground truth establishment for the test set is mentioned, as the predicate device's results served as the reference.
   • For the reproducibility study, "Each test was visually read by three independent readers with results masked." Reproducibility was then calculated based on agreement with a "modal zone diameter value." This implies a form of consensus or statistical assessment based on multiple reader interpretations, but not adjudication in the sense of resolving discrepancies to establish a single ground truth.

4. 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 MRMC comparative effectiveness study was done as this is an antimicrobial susceptibility test disc (a physical device), not an AI-powered diagnostic tool for human image interpretation.
   • The study design focused on the performance of the device itself compared to a predicate device, and the reproducibility of its readings, not on human reader performance with or without AI assistance.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

   • This is not an algorithm-only device. It is a physical disk that is interpreted by measuring the zone of inhibition. Therefore, the "standalone" performance here refers to the device's inherent ability to produce a measurable zone, which is then interpreted by a human operator according to established criteria. The study directly assesses this "standalone" device performance against a predicate and interpretive criteria.

6. The type of ground truth used:

   • The primary ground truth for comparing the BD BBL Sensi-Disc was the results obtained from an FDA-cleared disk (HardyDisk AST Cefiderocol 30μg), which itself would have established its performance against a gold standard (likely broth microdilution or another reference method) during its own clearance process.
   • Additionally, the performance of the BD device was implicitly judged against the FDA-identified interpretive criteria for Cefiderocol (Minimum Inhibitory Concentrations and Disk Diffusion zone diameters) listed in Table 4, which are derived from clinical data and expert consensus.
   • The study also mentions that some categorical agreement for the BD BBL Sensi-Disc Cefiderocol compared to historical BMD MIC values (Broth Microdilution Minimum Inhibitory Concentration) was below 90% for certain organisms, suggesting BMD MIC values are considered a gold standard, even if not directly used as the primary ground truth for the head-to-head comparison with the predicate disk.

7. The sample size for the training set:

   • The document does not explicitly mention a "training set" in the context of machine learning or AI. This is a traditional medical device (AST disc), not an algorithm that requires a training set. The isolates used in the study are for performance validation.

8. How the ground truth for the training set was established:

   • As there is no training set for an AI/ML algorithm, this question is not applicable. The device's manufacturing specifications and adherence to CLSI (Clinical and Laboratory Standards Institute) guidelines would be relevant for its development rather than a ground truth for training.

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