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The Fungitell® STAT assay is a protease zymogen-based colorimetric assay for the qualitative detection of (1->3)-B-D-glucan in the serum of patients with symptoms of, or medical conditions predisposing the patient to, invasive fungal infection. The serum concentration of (1->3)-B-glucan, a major cell-wall component of various medically important fungis, can be used as an aid in the diagnosis of deep-seated mycoses and fungemias . A positive result does not indicate which genus of fungi may be causing infection.

(1->3)-B-D-glucan index values should be used in conjunction with other diagnostic procedures, such as microbiological culture, histological examination of biopsy samples and radiological examination.

The Fungitell® STAT assay provides a qualitative measurement of (1-3)-D-Dglucan. The assay is based upon a modification of the Limulus Amebocyte Lysate (LAL) pathway. The Fungitell® STAT Reagent is modified to eliminate bacterial endotoxin reactivity and, thus, to only react to (1->3)-B-glucan, through the Factor Gmediated side of the pathway. (1->3)-3-D-glucan activates Factor G, a serine protease zymogen. The activated Factor G converts the inactive pro-clotting enzyme to the active clotting enzyme, which in turn cleaves the para-nitroanilide substrate, Boc-Leu-Gly-Arg-pNA, creating a chromophore, para-nitroaniline (pNA), that absorbs at 405 nm. The Fungitell® STAT kinetic assay is based upon the determination of the rate of optical density increase produced by a sample. This rate is interpreted against the rate of optical density increase of the Fungitell® STAT Standard to produce an index. This patient sample index value is qualitatively interpreted as a Negative, Indeterminate or Positive result according to the index value ranges provided in Table 1 below. The Fungitell® STAT Standard is calibrated at 80 +/- 8 pg/mL which is the Positive cut-off for the Fungitell® predicate.

Here's a summary of the acceptance criteria and study details for the Fungitell® STAT device, based on the provided document:

Acceptance Criteria and Device Performance

Study Details

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

   • Assay Cut-off study: 93 de-identified patient serum samples.
     • 44 Positive, 15 Indeterminate, and 34 Negative based on the predicate device Fungitell®.
   • Method Comparison study: 488 de-identified patient serum samples.
     • 309 Negative, 36 Indeterminate, and 143 Positive based on the predicate device Fungitell®.
   • Data Provenance: De-identified patient serum samples collected for routine clinical care of the intended population. Retrospective, as these were pre-existing samples. Country of origin not specified, but the study was performed at a CLIA laboratory, suggesting a US context.

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

   • The ground truth for the test set (both cut-off and method comparison studies) was established by comparing to the predicate device, Fungitell®. There is no mention of human experts directly establishing ground truth for these studies.

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

   • No adjudication method involving human readers is mentioned for the test set. All comparisons were made against the predicate device.

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 performed or mentioned. This is an in vitro diagnostic device, not an AI-assisted diagnostic.

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

   • Yes, the performance studies (Assay Cut-off, Method Comparison, Precision/Reproducibility) represent standalone performance of the Fungitell® STAT device. Its measurements and interpretations are independent of human-in-the-loop analysis beyond the initial sample collection and processing.

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

   • The primary ground truth used for performance evaluation was the results from the legally marketed predicate device, Fungitell®. The (1->3)-B-D-Glucan concentrations in the samples were distributed over the full measuring range of the predicate device's standard curve.

7. The sample size for the training set:

   • The document does not describe a separate "training set" in the context of machine learning. The Fungitell® STAT is a modified biochemical assay, not an AI/ML algorithm requiring a distinct training phase.

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

   • As there's no mention of an ML/AI model with a training set, this question is not applicable in the context of this device's development as described. The "calibration" of the Fungitell® STAT Standard (using Saccharomyces cerevisiae) was done against the predicate assay's glucan standard, which could be considered an analogous process to establishing a baseline reference.

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