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Qualitative culture and recovery of yeasts and fungi from blood

BACTEC Fungal Medium is a growth medium providing an aerobic environment for the detection of yeast and fungi. It has been designed for blood volumes of four to 10 mL, and is used specifically with BACTEC non-radiometric (NR) series instruments in the monitoring of clinical blood specimens for the presence of yeasts and fungi. BACTEC Fungal medium has a higher weight/volume concentration of dextrose and sucrose then the predicate device to enhance the recovery and CO2 production of yeast. Saponin was added to the BACTEC Fungal Medium as a lysing agent, and ferric ammonium citrate was added as a source of iron to stimulate recovery of fungi other than yeast. Resin was removed from this medium. Principles for detection of CO2 produced by microorganisms metabolizing blood culture medium nutrients are identical to the predicate device.

Here's a breakdown of the acceptance criteria and study details for the BACTEC® Fungal Medium, based on the provided 510(k) summary:

Acceptance Criteria and Device Performance

The acceptance criteria are implicitly derived from the comparative study against predicate devices (BACTEC® PLUS 26 Culture Vials and ISOLATOR™ Microbial Tubes/ISOSTAT® Microbial System). The goal is to demonstrate that the BACTEC® Fungal Medium performs "as good or better than" or "equivalent to" these predicate devices for the recovery of yeasts and fungi from blood, particularly in terms of recovery rates and speed of detection.

Study Details

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

   • BACTEC® Fungal Medium vs. BACTEC® PLUS 26:
     • Sample Size: 4886 adequately filled paired vials.
     • Data Provenance: Clinical study conducted at four university-affiliated hospitals. This indicates a prospective collection of real-world clinical samples. The country of origin is not explicitly stated but is implied to be the US given the submission to the FDA.
   • BACTEC® Fungal Medium vs. ISOLATOR™ Microbial Tubes/ISOSTAT® Microbial System:
     • Sample Size: 4907 adequately filled paired vials and tubes.
     • Data Provenance: Clinical study conducted at four university-affiliated hospitals. This indicates a prospective collection of real-world clinical samples. The country of origin is not explicitly stated but is implied to be the US.

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

   • This information is not provided in the summary. The "ground truth" for recovery is based on the actual growth and identification of microorganisms from the culture media, which would typically be performed by trained laboratory personnel (microbiologists/medical technologists). The summary does not specify the number or qualifications of these individuals.

3. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

   • This information is not explicitly stated. For microbiology studies, "adjudication" in the traditional sense of multiple readers reviewing images isn't directly applicable. Instead, the results are likely determined by standard laboratory protocols for organism identification and confirmation.

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, this was not an MRMC comparative effectiveness study involving human readers and AI assistance. This study evaluates the performance of different microbial culture media, an in vitro diagnostic device, not an AI-powered diagnostic imaging system.

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

   • Yes, in a sense, this was a "standalone" evaluation of the media. The BACTEC instrument automatically detects CO2 production. The study evaluates the medium's ability to support growth detectable by the instrument, without human intervention in the primary detection phase, although humans perform subsequent identification of the isolates.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

   • The ground truth was established by microbiological culture and identification of isolates recovered from the blood samples. This is considered the gold standard for detecting and identifying microorganisms in blood cultures. "Clinically significant isolates" implies a determination by a clinician or microbiologist that the isolated organism is relevant to the patient's condition.

7. The sample size for the training set:

   • This information is not explicitly provided. The study describes "clinical performance" testing, which typically refers to the final validation set for regulatory submission. Details of earlier development or optimization ("training") sample sizes for the medium formulation are not usually included in a 510(k) summary. The formulation of the medium itself is a scientific development process, not an AI training process.

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

   • As with the training set, details on how ground truth was established during the development or "training" phase of the medium formulation are not in this summary. However, it would similarly have involved microbiological culture and identification methods to assess the growth characteristics of various target microorganisms in different medium formulations.

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