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The Curian Shiga Toxin assay, for use with the Curian Analyzer, is a rapid, qualitative, fluorescent immunoassay for the simultaneous detection and differentiation of Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) in a single test device. It is intended for use with cultures derived from human stool specimens to aid in the diagnosis of disease caused by Shiga toxin producing Escherichia coli (STEC) infections. Test results are to be used in conjunction with the patient's clinical symptoms and history.

The Curian® Shiga Toxin assay is a qualitative in vitro diagnostic test for the detection of Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) in cultures derived from human stool specimens. The Curian® Shiga Toxin assay utilizes fluorescence technology with the cleared Curian® Analyzer (K192817) to detect Stx1 and Stx2 in cultures derived from human stool.

Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:

1. Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria, but it presents the performance of the Curian Shiga Toxin assay against a reference method (Vero cell Cytotoxin Assay). We can infer the implicit acceptance criteria from the reported performance, which demonstrates high sensitivity and specificity.

Note: The low end of the 95% CI for sensitivity in prospective specimens (e.g., 56.6% for Stx1) is due to the very small number of positive cases in that cohort (5 for Stx1 and 4 for Stx2). The 100% point estimate, while positive, has a wide confidence interval reflecting this small sample size. The archived cohort provides more robust sensitivity estimates.

2. Sample Size Used for the Test Set and Data Provenance

• Prospective Test Set: 1,627 stool specimens collected from patients suspected of having a Shiga toxin-producing Escherichia coli (STEC) infection.
  • Evaluable Prospective Specimens: 1,538
  • Data Provenance: Prospective collection from five clinical study sites representing geographically distinct regions throughout the United States.
• Archived Test Set: 140 archived stool samples.
  • Evaluable Archived Specimens: 135 (5 excluded due to inconclusive reference results).
  • Data Provenance: Retrospective testing of archived samples at all five clinical study sites.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

The document does not explicitly state the number of experts or their qualifications for establishing the ground truth. It mentions that the reference method was the "Vero cell Cytotoxin Assay (with neutralization) performed on the broth culture obtained from the stool specimen." This is a laboratory-based assay, and its interpretation would typically be performed by trained laboratory personnel rather than a panel of clinical experts (e.g., radiologists).

4. Adjudication Method for the Test Set

The document does not describe any adjudication method for the test set. The ground truth was established by the "Vero cell Cytotoxin Assay (with neutralization)."

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, an MRMC comparative effectiveness study was not conducted. This device is an in vitro diagnostic (IVD) assay interpreted by an analyzer, not a medical imaging or diagnostic aid that multiple human readers would interpret with and without AI assistance. The Curian Analyzer automates the interpretation of results ("Results interpretation automated by Curian® Analyzer").

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, the clinical performance study (both prospective and archived) represents the standalone performance of the device (Curian Shiga Toxin assay and Curian Analyzer). The results are "produced by the Curian Analyzer," indicating an automated, algorithm-only interpretation without a human-in-the-loop performance evaluation in the context of these clinical studies.

7. The Type of Ground Truth Used

The type of ground truth used was a laboratory reference method: the Vero cell Cytotoxin Assay (with neutralization) performed on broth cultures obtained from the stool specimens.

8. The Sample Size for the Training Set

The document does not provide information about the sample size for a training set. This is common for IVD submissions, where the focus is on the analytical and clinical performance of the device itself rather than the development of the underlying algorithms through a specific training set. The device is a "lateral flow fluorescent immunoassay," which is a biochemical detection method, not a machine learning algorithm that typically requires a large training dataset in the same way.

9. How the Ground Truth for the Training Set Was Established

Since no training set information is provided, there is no description of how ground truth for a training set was established.

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Curian Campy, for use with the Curian Analyzer, is a rapid, qualitative fluorescent immunoassay for the detection of a Campylobacter-specific antigen in human fecal specimens. Curian Campy is intended to detect C. jejuni, C. coli, C. upsaliensis, and C. lari in human stool from patients with signs and symptoms of gastroenteritis. The test is intended for use with unpreserved fecal specimens or preserved fecal specimens in transport media. Test results are to be used in conjunction with information available from the patient clinical evaluation and other diagnostic procedures. Curian Campy is intended to aid in the diagnosis of Campylobacter infection.

The Curian® Campy assay is a qualitative in vitro diagnostic test for the detection of Campylobacter-specific antigens in human stool samples collected from individuals with signs and symptoms of gastroenteritis. Curian Campy is intended to detect C. jejuni, C. coli, C. upsaliensis, and C. lari in unpreserved or preserved stool in Cary-Blair or C&S transport media. The Curian® Campy assay utilizes fluorescence technology with the cleared Curian® Analyzer (K192817) to detect Campylobacter-specific antigens in human stool.

Here's a breakdown of the acceptance criteria and study details for the Curian Campy device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" as a separate section with predefined thresholds. However, based on the presentation of clinical performance data, the implicit acceptance criteria for sensitivity and specificity are demonstrated by the confidence intervals achieved in the clinical studies. For analytical performance, 100% agreement for certain categories and no observed interference/cross-reactivity are the implicit acceptance criteria.

2. Sample Sizes Used for the Test Set and Data Provenance

• Prospective Clinical Study:
  • Sample Size: 1,474 specimens
  • Data Provenance: Prospective, collected from July 2020 to December 2020 at five clinical study sites across geographically distinct regions throughout the United States.
• Archived Clinical Study:
  • Sample Size: 290 archived samples
  • Data Provenance: Retrospective. The samples had prior culture and speciation results and were retrospectively tested.
• Contrived Study:
  • Sample Size: 210 specimens (150 positive, 60 negative).
  • Data Provenance: Contrived samples (spiked with Campylobacter species).
• Reproducibility Study:
  • Sample Size: 320 samples (160 unpreserved stool, 160 preserved stool in C&S media).
  • Data Provenance: Contrived samples, tested across three sites (one internal, two external).
• Prozone / Hook Effect Study:
  • Sample Size: 14 dilutions (n=7 for preserved, n=7 for unpreserved) tested in replicates of 5.
  • Data Provenance: Contrived samples.
• Cross-Reactivity/Microbial Interference Study:
  • Sample Size: Not explicitly stated as a number, but involves testing various bacteria, fungi, and viral strains (spiked into stool, some clinical Norovirus samples).
  • Data Provenance: Primarily contrived samples, with 5 clinical Norovirus stool specimens.
• Interfering Substances Study:
  • Sample Size: Not explicitly stated, but involves testing C. jejuni low positive contrived samples in the presence of 27 different chemical and biological substances.
  • Data Provenance: Contrived samples.
• Assay Reactivity/Inclusivity Study:
  • Sample Size: Not explicitly stated, but involves testing multiple strains of C. jejuni, C. coli, C. upsaliensis, and C. lari.
  • Data Provenance: Laboratory strains.
• Brush Bridging Study:
  • Sample Size: 53 non-pipettable clinical stool specimens (5 positive, 48 negative) from the prospective and archived clinical studies, plus a panel of contrived samples (25 at 3x LoD, 25 at 5x LoD, 25 negative).
  • Data Provenance: Clinical (from prior studies) and contrived.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

• Ground Truth for Clinical Studies (Prospective and Archived): The ground truth was established by "standard of care Campylobacter culture and speciation" which is a laboratory method. There is no mention of human experts directly establishing the ground truth for classification of individual samples.
• Ground Truth for Contrived Studies (Reproducibility, Analytical Sensitivity, Prozone, Cross-Reactivity, Interfering Substances, Assay Reactivity): The ground truth was established by creating samples with known concentrations of organisms or by confirming the absence of organisms. This suggests laboratory verification rather than expert clinical assessment.

4. Adjudication Method for the Test Set

• Prospective Clinical Study: For specimens with discordant results between the Curian Campy assay and the reference method (culture and speciation), further evaluation was done using "FDA-cleared commercial nucleic acid amplification test (NAAT)". This acts as a form of adjudication for discordant results, though it's not a human consensus process.
• Archived Study, Contrived Studies, Analytical Performance Studies: No adjudication method is explicitly described for these studies other than the initial ground truth determination.

5. 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.
• This device is an in-vitro diagnostic assay (Curian Campy) read by an automated analyzer (Curian Analyzer), not an AI assisting human readers. Therefore, the concept of "human readers improve with AI vs without AI assistance" does not apply.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done

• Yes, the performance data presented for the Curian Campy assay is standalone. The device (Curian Campy assay with the Curian Analyzer) provides a qualitative result (positive/negative) automatically. The interpretation of results is "automated by Curian Analyzer," and the clinical studies directly evaluate this automated output against a reference standard.

7. The Type of Ground Truth Used

• Clinical Studies (Prospective and Archived): The primary ground truth was culture and speciation for Campylobacter. For discordant results in the prospective study, an FDA-cleared commercial nucleic acid amplification test (NAAT) was used for further evaluation.
• Analytical Performance Studies (Reproducibility, Analytical Sensitivity, Prozone, Cross-Reactivity, Interfering Substances, Assay Reactivity, Contrived Study): The ground truth was based on known concentrations of spiked organisms or known negative samples, verified by laboratory methods.

8. The Sample Size for the Training Set

• The document does not describe algorithmic training. This device appears to be a fluorescence immunoassay interpreted by an analyzer, not a machine learning or AI algorithm that requires a separate training set. The descriptions of "analytical performance" and "clinical performance" are for evaluating the performance of the device itself, not for training an AI model.

9. How the Ground Truth for the Training Set was Established

• As there is no mention of an AI algorithm requiring a training set, this question is not applicable to the information provided.

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