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BacT/ALERT® FA Plus Culture Bottles are used with BacT/ALERT® Microbial Detection Systems in qualitative procedures for recovery and detection of aerobic microorganisms (bacteria and yeast) from blood and other normally sterile body fluids.

BacT/ALERT® PF Plus Culture Bottles are used with BacT/ALERT® Microbial Detection Systems in qualitative procedures for recovery and detection of aerobic microorganisms (bacteria and yeast) from blood.

The BacT/ALERT® Microbial Detection Systems utilizes a colorimetric sensor and reflected light to monitor the presence and production of carbon dioxide (CO2) dissolved in the culture medium. If microorganisms are present in the test sample, carbon dioxide is produced as the microorganisms metabolize the substrates in the culture medium. When growth of the microorganisms produces CO2 the color of the gas-permeable sensor installed in the bottom of each culture bottle changes from blue-green to yellow. The lighter color results in an increase of reflectance units monitored by the system. Bottle reflectance is monitored and recorded by the instrument every 10 minutes.

BacT/ALERT® Microbial Detection Systems are used to determine if microorganisms are present in blood or other normally sterile body fluid samples taken from a patient suspected of having bacteremia/fungemia. The BacT/ALERT® Systems and culture bottles provide both a microbial detection system and a culture medium with suitable nutritional and environmental conditions for organisms commonly encountered in blood infections and other normally sterile body fluid infections. An inoculated bottle is placed into the instrument where it is incubated and continuously monitored for the presence of microorqanisms that will grow in the BacT/ALERT® FA Plus or PF Plus Culture Bottle (The BacT/ALERT® PF Plus Culture Bottle provides for detection of microorganisms when a small volume of blood is available.).

The provided text describes the performance characteristics of the BacT/ALERT® FA Plus and BacT/ALERT® PF Plus culture bottles, which are microbial detection systems. The study aims to demonstrate the equivalency of a modified formulation of these devices to their predicate devices.

Here's an analysis of the acceptance criteria and study details:

1. Table of Acceptance Criteria and Reported Device Performance

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BacT/ALERT® FA Plus Culture Bottles are used with the BacT/ALERT® Microbial Detection System in qualitative procedures for enhanced recovery and detection of aerobic and facultative anaerobic microorganisms (bacteria and yeast) from blood and other normally sterile body fluids.

The new reagent (BacT/ALERT FA Plus Culture Bottle) is an improvement upon the cleared charcoal formulation reagent (BacT/ALERT FA Culture Bottle). The BacT/ALERT FA Culture Bottles are used with the BacT/ALERT Microbial Detection Systems in qualitative procedures for recovery and detection of microorganisms from blood. The predicate BacT/ALERT FA Culture Bottle contains charcoal, for its antimicrobial neutralization properties, in a complex growth medium. Charcoal is eliminated in the proposed BacT/ALERT FA Plus Culture Bottle, and is replaced with two types of adsorbent resins in a complex growth medium. The proposed BacT/ALERT FA Plus Culture Bottle is optimized to increase antimicrobial neutralization properties, and to increase the clarity of Gram stains in comparison to the predicate BacT/ALERT FA Culture Bottle. The BacT/ALERT Microbial Detection System provides both a microbial detection system and a culture medium bottle with suitable nutritional and environmental conditions for microorganisms commonly encountered in blood or other normally sterile body fluid samples (except urine) taken from a patient suspected of having bacteremia/fungemia. An inoculated bottle is placed into the instrument where it is incubated and continuously monitored for the presence of microorganisms that will grow in the BacT/ALERT bottles. The BacT/ALERT Microbial Detection System utilizes a colorimetric sensor and reflected light to monitor the presence and production of carbon dioxide (CO2) that is dissolved in the culture medium. If microorganisms are present in the test sample, carbon dioxide is produced as the microorganisms metabolize the substrates in the culture medium. When growth of the microorganisms produces CO2, the color of the gas-permeable sensor installed in the bottom of each culture bottle changes from blue-green to yellow. The lighter color results in an increase of reflectance units monitored by the system. Bottle reflectance is monitored and recorded by the instrument every 10 minutes.

Here's a breakdown of the acceptance criteria and study information for the BacT/ALERT® FA Plus Culture Bottle, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are generally demonstrated by the recovery rates and detection times remaining consistent with or improved compared to the predicate device, or meeting specific thresholds for sensitivity (LoD) and reproducibility.

2. Sample Sizes and Data Provenance

• Analytical Sensitivity (Growth Performance):
  • Test Set Sample Size: Varies by microorganism (e.g., 33/33, 15/15), generally small per species, but covering n replicates.
  • Data Provenance: In-house seeded studies. Blood obtained from healthy human volunteers.
• Limit of Detection (LoD):
  • Test Set Sample Size: Minimum of 30 replicates per species.
  • Data Provenance: In-house seeded studies, using bottles at end of shelf life.
• Within-Laboratory Precision (Repeatability):
  • Test Set Sample Size: Minimum of 108 replicates (organism/antimicrobial combination) over 12 days.
  • Data Provenance: In-house seeded studies
• Reproducibility:
  • Test Set Sample Size: Target of 162 replicates per site across 3 sites (total of 486).
  • Data Provenance: Seeded studies at three sites (implicitly internal or contract labs).
• Delayed Entry:
  • Test Set Sample Size: Target concentrations of 100 CFU per bottle (35 to 290 CFU/bottle actual inoculum). At least 11 species. Control: 459 bottles. Held conditions: ~296-459 bottles per condition.
  • Data Provenance: Seeded studies at three sites. Human blood from healthy volunteers.
• Clinical Study (Blood Cultures):
  • Test Set Sample Size: 1656 bottle pairs (from 728 adult patients). Total 1685 results (267 isolates + 1418 negative pairs).
  • Data Provenance: Multi-center clinical study at three different geographic sites in the U.S. Prospective (implied, as it compares performance).
• Clinical Study (Sterile Body Fluid Cultures):
  • Test Set Sample Size: 404 bottle pairs (from 369 adult patients). Total 421 results (92 isolates + 329 negative pairs).
  • Data Provenance: Multi-center clinical study at four different geographic sites in the U.S. and Canada. Prospective (implied).

3. Number of Experts and Qualifications for Ground Truth

• For all seeded studies (Analytical Sensitivity, LoD, Repeatability, Reproducibility, Delayed Entry), the ground truth is established by the known inoculum of microorganisms and subsequent culture confirmation/gram stain. No external experts are mentioned for these in-vitro studies beyond the internal study design and execution.
• For Clinical Studies (Blood and SBF Cultures):
  • Number of Experts: Not explicitly stated.
  • Qualifications of Experts: The text states, "Clinical isolates recovered were classified as significant, contaminant, or unknown based on determination by the clinical trial sites." This implies clinical microbiologists, infectious disease physicians, or other qualified laboratory personnel at the participating clinical sites were responsible for this determination. Specific qualifications (e.g., years of experience) are not provided.

4. Adjudication Method for the Test Set

• For seeded studies, adjudication is not typically performed in the same way as clinical imaging studies. The "ground truth" is directly controlled by the known seeded organisms and concentrations, and confirmed by lab methods (subculture, Gram stain).
• For Clinical Studies (Blood and SBF Cultures):
  • "A pair of bottles was determined to have a positive status if the subculture of either the FA Plus or FA bottle was positive."
  • "A culture bottle was determined to be a 'True Positive' if the culture was flagged positive by the BacT/ALERT System and resulted in growth of the isolate upon subculture of this bottle."
  • "Clinical isolates recovered were classified as significant, contaminant, or unknown based on determination by the clinical trial sites."
  • This indicates that subcultures and expert determination at the clinical sites served as the primary adjudication method for classifying positive results and the significance of isolates. No explicit 2+1 or 3+1 "expert consensus" model is described beyond the site-level determination.

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

• No MRMC study was performed in the context of human readers improving with AI assistance. This device is a microbial detection system, not an AI diagnostic imaging tool that assists human readers.
• The clinical studies performed compare the performance of the new BacT/ALERT® FA Plus Culture Bottle to the predicate BacT/ALERT® FA Culture Bottle in a "bottle pair" design, which is a comparative effectiveness study of two devices, not human-AI interaction.
• The "effect size" mentioned, such as the ratio of true positives (e.g., 1.178 for significant blood isolates), represents the improved detection by the new bottle type compared to the previous one, not human reader improvement with AI.

6. Standalone Performance Study

• Yes, the device's performance, as measured by its ability to recover and detect microorganisms, is evaluated in a standalone manner. All the analytical (seeded) studies (Analytical Sensitivity, LoD, Repeatability, Reproducibility, Delayed Entry) are assessments of the algorithm/device performance without human-in-the-loop directly influencing the detection flagging.
• The clinical studies also report the device's performance (true positives, false positives) based solely on its output and subsequent lab confirmation, demonstrating its standalone effectiveness in a clinical setting.

7. Type of Ground Truth Used

• For all seeded studies: The ground truth is the known identity and concentration of the microorganisms inoculated into the bottles, confirmed by post-detection laboratory methods (e.g., Gram stain, subculture).
• For clinical studies: The ground truth is established through subculture of flagged positive bottles and subsequent determination of isolate significance (significant, contaminant, unknown) by the clinical trial sites. This combines direct microbiological evidence with clinical judgment.

8. Sample Size for the Training Set

• The document does not explicitly mention a "training set" in the context of machine learning or AI model development. This device is a culture medium and detection system, not a software algorithm that learns from a training dataset in the typical AI sense.
• The mention of "knowledge base specifications utilized by the firmware included changes to the initial value threshold variables" suggests that some parameters of the detection algorithm were likely tuned or established based on internal development data, but this is not described as a formal "training set" with separate validation.

9. How Ground Truth for Training Set was Established

• As mentioned above, there is no explicit "training set" described for an AI model. The system relies on chemical reactions (CO2 production changing sensor color) and firmware interpreting these changes, with threshold adjustments.
• Any ground truth used to optimize these firmware thresholds would have likely come from internal R&D studies, similar to the "in-house seeded studies" described for performance testing, where the presence and growth of organisms are known and confirmed microbiologically.

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