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Beckman Coulter's iTAg MHC Tetramer-CMV is for the identification and enumeration of cytomegalovirus (CMV) -specific CD8+ lymphocytes in whole blood by flow cytometry, and for the assessment of CMV-specific immune status in immunosuppressed stem cell transplant recipients. The assay is limited to individuals with the following HLA types: A0101, A0201, B0702, B0801, B*3501.

iTAg™ MHC Tetramer CMV is similar to existing CD (cluster differentiation) technology, measuring subsets of an individual's total leukocyte population. The tetramer kits include five tetramers specific for particular CD3+CD8+ cell receptors. While 5 alleles are provided for this assay, an individual's analysis may use up to 4 of these 5 tetramers. Tetramers enumerate CD3+CD8+ subsets by flow cytometry, similar to antibodies: Same specimen (whole blood), indication (identification and enumeration of lymphocyte populations), platform (flow cytometry), fluorochromes, Flow-Count Fluorospheres, and accessory reagents. The assay components include: Vials of anti-CD8 FITC, Vials of anti-CD4 PE, Vials of anti-CD3 PC5, Vials of Flow-Count Beads, Vials of lysing agent, Vials of fixative, Up to 5 vials of individual Tetramers labeled with PE, Vials of negative Tetramer labeled with PE.

Here's a breakdown of the acceptance criteria and study information for the iTAg MHC Tetramer-CMV device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance:

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

The document does not explicitly state a specific sample size for a "test set" in the context of typical algorithm validation (e.g., retrospective images for AI). Instead, the "Summary of Studies" describes a series of analytical performance evaluations using various samples.

• Sample Size: Not explicitly stated as a single number.
  • Linear Range, Accuracy and Recovery, Analytical Sensitivity: "the sample tested" (for linearity), "three tetramers" (for recovery), "samples" (for sensitivity).
  • Reproducibility: Not specified beyond the general nature of samples for intra- and inter-laboratory tests.
  • Expected Reference Range: "apparently healthy CMV sero-negative donors" and "apparently healthy CMV sero-positive donors" – the number of donors is not specified.
  • Clinical Data: "samples were HLA-typed and tested for CMV immune status by immunoassay" from "immunosuppressed stem cell transplant recipients." The precise number of clinical samples is not specified.
• Data Provenance:
  • The studies were performed at Beckman Coulter Inc. facilities, and some inter-laboratory reproducibility studies involved "two external sites."
  • The clinical data involved "immunosuppressed stem cell transplant recipients" and "apparently healthy CMV sero-negative donors" and "CMV sero-positive donors," indicating human biological samples.
  • The nature of the studies (e.g., "Expected Reference Range," "Clinical Data") implies prospective collection or analysis of these donor/patient samples, though not explicitly stated as "prospective" or "retrospective" in a research study design sense. It's likely prospective collection of fresh samples/blood for laboratory characterization.

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

This information is not provided in the document. The studies described are methodologic performance evaluations (e.g., linearity, reproducibility, sensitivity) and instrument comparisons, not evaluations of a diagnostic algorithm against human expert interpretation. The "ground truth" for these types of studies is typically derived from established laboratory methods, reference materials, or a "gold standard" instrument/assay.

4. Adjudication Method for the Test Set:

This information is not applicable and not provided. There's no mention of expert adjudication for establishing ground truth, as the studies focus on analytical performance rather than diagnostic accuracy based on human interpretation.

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

This information is not applicable and not provided. The device (iTAg MHC Tetramer-CMV) is a laboratory assay (an automated differential cell counter in the context of its classification) that identifies and enumerates specific cell populations using flow cytometry. It is not an AI-powered diagnostic imaging device that human readers would interpret or use an AI assistant with. Therefore, an MRMC study comparing human readers with or without AI assistance is not relevant to this device.

6. Standalone (Algorithm Only) Performance:

Yes, the studies describe standalone performance. The iTAg MHC Tetramer-CMV, being a laboratory assay, is evaluated for its inherent analytical capabilities (specificity, linearity, accuracy, sensitivity, reproducibility, instrument comparability) without explicit human intervention in the measurement process itself, beyond standard laboratory procedures for sample handling and instrument operation. The results reported (e.g., 96% recovery, CVs, regression coefficients) are precisely the standalone performance of the assay and the associated flow cytometry system.

7. Type of Ground Truth Used:

The ground truth used for the analytical studies described appears to be a combination of:

• Expected values/reference methods: For linearity, accuracy, and recovery studies, the "expected values" or comparison against established methods serve as the ground truth.
• Established laboratory techniques: The enumeration of cell populations and determination of characteristics like specificity likely rely on well-defined flow cytometry principles and expert validation of populations.
• CMV serological status and HLA typing: For the clinical utility aspect, the samples were "HLA-typed and tested for CMV immune status by immunoassay," which would serve as the ground truth for classifying patients for the clinical utility assessment.
• Reference instruments: For instrument comparison, the "BD FACSCalibur flow cytometer" and "BCI EPICS-XL flow cytometer" and "BCI FC500 flow cytometer" serve as the reference/comparative ground truth.

8. Sample Size for the Training Set:

This information is not provided and is likely irrelevant in the context of this device. The iTAg MHC Tetramer-CMV is a reagent kit used with flow cytometers, not a machine learning or AI algorithm that requires a "training set" in the conventional sense. Its performance is based on the biochemical and physical properties of the tetramers and the established analytical capabilities of flow cytometry.

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

This information is not provided and likely irrelevant for the same reasons as (8). As it's not an AI/ML device, the concept of a "training set" and associated ground truth establishment for model training does not apply.

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