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The OSOM iFOB (Immunochemical Fecal Occult Blood) Test is a rapid immunoassay for the qualitative detection of fecal occult blood by laboratories or physicians' offices. It is useful for the detection of human hemoglobin in human fecal samples and is recommended for use as part of routine physical examinations or when lower gastrointestinal disorders are suspected.

The OSOM iFOB (Immunochemical Fecal Occult Blood) Test is a rapid test which can detect the presence of occult blood in human fecal samples by detecting the presence of human hemoglobin (hHb). The OSOM iFOB Test is a qualitative assay that employs immuochromatographic, lateral flow technology. A test kit contains 25 pouched Test Devices, 25 Extraction Reagent vials, 25 conjugate vial tips, and 25 sample collection packs. Tests and Reagents are also available in a 50-test kit without sample collection packs, and sample collection packs are available separately in a package of 50. Negative and positive external controls are provided separately as the OSOM iFOBT Control Kit.

The fecal sample collected using an OSOM iFOB sample collection card is placed into a prefilled vial containing Extraction Buffer. This test solution is then dispensed, through a dropper tip containing human hemoglobin antibody conjugated to latex, into the sample well of the Test Device. The sample migrates across the membrane containing a Test line coated with anti-human hemoglobin antibody and a Control line. If hemoglobin is present at or above the level of detection of the test, an antigen/antibody complex will be formed. The appearance of a visible blue Test line and a red Control line in the result window indicates the presence of human hemoglobin in the sample. A red control line must appear for the results to be valid. If a detectable level of hemoglobin is not present, only the red control line will appear. An invalid test occurs when no control line appears.

The control line serves as an internal procedural control, indicating that the test system is functioning correctly and that the operator added a sufficient volume of sample. In addition to the internal control in each Test Device, external controls are available in a separate OSOM iFOBT Control Kit. The Negative Control (buffer solution) and the Positive Control (hHb in buffer solution) are run in the iFOB Test in the same manner as an extracted fecal sample.

Here's a breakdown of the acceptance criteria and study details for the OSOM iFOB Test, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" in a formal, enumerated list with specific thresholds for each performance metric. However, we can infer the acceptance criteria from the study's design and the conclusions drawn about "reproducibility" and "substantial equivalence." The main inferred acceptance criteria revolve around achieving high agreement with expected results and with a predicate device.

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

• Reproducibility and Detection Limit Study:
  • Sample Size: 542 individual test results were reported (325 expected positive, 217 expected negative). This was composed of panels of 15 test samples (3 of each of 5 hemoglobin concentrations: 0, 37.5, 50, 62.5, and 2000 ng/mL hHbA). Each POL operator tested 1 panel on each of 3 lots of the device. The reference site tested the same number of samples as the three external sites. Given 3 POL sites * 3 operators/site * 1 panel/operator/lot * 3 lots = 27 panels. The reference site also tested an equivalent amount. The specific number of unique samples is not directly stated, but the total number of test repetitions is 542.
  • Data Provenance: Retrospective, using spiked fecal samples with known concentrations of human hemoglobin A. The samples are prepared specifically for the study.
• Method Comparison Study:
  • Sample Size: 125 individual test results (75 expected positive, 50 expected negative based on predicate device). This involved 25 replicates of each of the five hemoglobin concentrations (0, 37.5, 50, 62.5, and 2,000 ng/mL hHbA).
  • Data Provenance: Retrospective, using spiked fecal samples with known concentrations of human hemoglobin A. The samples are prepared specifically for the study.
• Sensitivity to Hemoglobin Variants, Hook Effect, Cross-Reactivity, and Interfering Substances:
  • Sample Size: Specific numbers of discrete samples are not explicitly provided for these studies, but they involve testing various concentrations of hHbS, hHbC, potential cross-reactants, and interfering substances with three lots of the OSOM iFOB Test.
  • Data Provenance: Retrospective, using prepared samples (spiked with specific substances) rather than naturally occurring patient samples.

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

• Number of Experts: For the reproducibility study, expert oversight established the testing protocol. However, the ground truth for spiked samples is determined by the known concentration of human hemoglobin A added to the fecal samples, not through expert reading of results.
  • Reproducibility study: "Testing at Sekisui Diagnostics, the reference site, was performed by two experienced laboratory professionals." These professionals performed the testing, but the ground truth (expected positive/negative) was based on the known spiked hemoglobin concentrations. The "intended users" at external POL sites also performed testing, with varying levels of education and work experience.
  • Method Comparison study: The "ground truth" for the OSOM iFOB Test was effectively established by direct comparison to the predicate device (Alfa Instant-View FOB Rapid Test / QuickVue iFOB Test) which itself is cleared as substantially equivalent. The ground truth for the spiked samples themselves was the known hemoglobin concentration.
• Qualifications of Experts: For the Sekisui Diagnostics reference site, "two experienced laboratory professionals" are mentioned. For the external POL sites, it stated "3 intended users per site, with varying levels of education and work experience," implying they are general laboratory or physician office personnel, not necessarily "experts" in establishing ground truth, but rather representative end-users.

4. Adjudication Method for the Test Set

The concept of "adjudication" in the sense of multiple external experts reviewing results to establish a definitive ground truth is not applicable here.

• For the reproducibility and detection limit studies, the ground truth was analytically determined by the known concentrations of spiked human hemoglobin. Samples with 0 and 37.5 ng/mL were expected negative, and samples with 50, 62.5, and 2000 ng/mL were expected positive, based on the device's stated detection level of 50 ng/mL. Any discrepancies between the device result and this analytically derived "expected" result were simply tallied for agreement calculation.
• For the method comparison study, the "ground truth" for comparison was the result obtained by the predicate device (QuickVue iFOB Test) on the same spiked samples, with the ultimate ground truth being the known spiked concentrations.

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

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study comparing human readers with AI assistance versus without AI assistance was not done.

This device (OSOM iFOB Test) is a lateral flow immunoassay for detecting occult blood, not an AI-powered diagnostic system that assists human readers in interpreting complex medical images or data. The "readers" mentioned in the reproducibility study (POL operators) are simply the end-users performing the physical test, not interpreting an AI output.

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

Yes, the performance studies primarily reflect the standalone performance of the device.

The OSOM iFOB Test itself is a rapid immunoassay that produces a visible result (lines on a test strip). While a human operator (the "intended user" or "laboratory professional") has to perform the steps and visually interpret the lines, the core mechanism and output are inherent to the device's chemical and immunochromatographic properties. The studies evaluate the device's ability to accurately provide this result in various conditions, independent of active "human-in-the-loop" interpretive assistance beyond basic observation. The reproducibility study explicitly tested the ability of different users to get consistent results, which is a test of the device's robustness across user variability rather than a human-machine interface evaluation.

7. The Type of Ground Truth Used

The ground truth for all performance studies was primarily analytically determined via known concentrations of spiked human hemoglobin.

• For the reproducibility, detection limit, sensitivity to variants, and hook effect studies, the ground truth was the known concentration of hemoglobin (hHbA, hHbS, hHbC) added to the fecal samples, which then dictated the expected positive or negative result based on the device's detection threshold.
• For the cross-reactivity and interfering substances studies, the ground truth was the known absence or presence of specific interfering/cross-reacting substances along with, for interference, the known presence of hHbA at a critical concentration.
• For the method comparison study, the ground truth was a combination of the known spiked hemoglobin concentrations and the results from a legally marketed predicate device (Alfa Instant-View FOB Rapid Test / QuickVue iFOB Test).

8. The Sample Size for the Training Set

The document does not describe a "training set" in the context of an algorithm or machine learning device.

The OSOM iFOB Test is an immunochromatographic assay, not a device that employs algorithms that require training data. The development of the test (e.g., antibody selection, membrane optimization) would have involved extensive R&D, but this is not typically referred to as a "training set" in the sense used for AI/ML.

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

As there is no "training set" in the context of AI/ML, this question is not applicable. The device's underlying chemistry and biology are its "rules," not a learned algorithm.

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