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The EXCELL™ 22, is an in-vitro diagnostic instrument for use in counting blood cells, classifying white blood cells (WBC) and flagging specimens containing abnormal blood cells in clinical laboratories at diverse sites. Per NCCLS H20A section 4(9), flagging is defined as "identifying a sample or blood film for further attention or review".

The EXCELL 22 is a DATACELL 18MS with an additional optical channel for performing a five-part white cell differential. The five-part optical white cell differential system is substantially equivalent to the Cell-Dyn 3000.

Modifications to the DATACELL 18MS present in the new instrument are:

• Addition of a laser excited multi dimensional flow cytometer .
• . addition of a reagent for the optical flow cell
• provision for collecting data from the optical detectors .
• replacing of AC motors with DC motors to make the product suitable . for international applications
• replacing the internal PC computer and monitor with an external PC to . gain room for the optical detection system
• . provision in the slide valve for the additional dilution for the WBC optical measurement
• . addition of hydrodynamic focus sample injection system for the WBC
• improved dilution logic to speed up the measurement .
• improved platelet aperture system called the von Behrens silencer.

The operating modes are the same as the DATACELL 18MS.

Here's a summary of the acceptance criteria and the study that proves the device meets them, 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

• Study 1 (Accuracy/Correlation):
  • Initial Sample Size: 390 whole blood samples.
  • WBC Differential Count Portion: Reduced to 268 samples after eliminating morphological positive results on reference and test instruments (as recommended in NCCLS H20-A).
  • PLT, RBC, MCV, RDW, HGB Portion: Reduced to 326 samples after eliminating morphological positive results on reference and test instruments (as recommended in NCCLS H20-A).
  • Provenance: "Obtained from various sources including physicians' offices and hospital laboratories." (Likely domestic, but not explicitly stated. Retrospective for Study 1, as samples were collected and then tested without intervention to the patient population.)
• Study 2 (Flagging Characteristics):
  • Sample Size: 173 whole blood samples.
  • Provenance: "Obtained from various sources." (Likely domestic, but not explicitly stated. Retrospective for Study 2, as samples were collected and then tested.)

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

• Number of Experts: Three different technologists were used for the manual differential count in Study 2.
• Qualifications: Not explicitly stated beyond "technologists." Standard practice for manual differentials implies proficiency and training in hematology.

4. Adjudication Method for the Test Set

• For Study 2 (Flagging Characteristics), when a DIFF flag was reported by either the EXCELL 22 or Cell-Dyn 3000, "three different technologists performed a manual differential count. The manual count from each technologist was recorded, and the average result of all three was used in order to minimize the effects of human error and to improve statistical confidence of the observation." This is a form of 3-reader averaging.

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

• No, an MRMC comparative effectiveness study for human readers with and without AI assistance was not conducted or reported. This study focused on the performance of the automated device against predicate devices and manual counts, not on improving human reader performance with AI.

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

• Yes, the entire study focuses on the standalone performance of the EXCELL 22 automated analyzer. Its performance is compared directly against predicate devices (Cell-Dyn 3000, Coulter S+IV) and, for flagging differences, against averaged manual differential counts.

7. The Type of Ground Truth Used

• Accuracy/Correlation Studies (Study 1): The ground truth was established by two commercially available, legally marketed predicate devices: the Cell-Dyn 3000 (for WBC differential) and the Coulter S+IV (for basic hematology parameters). The text states: "Because no established standards are available for hematology analyzers, instruments were compared with a calibrator stated to be calibrated to a commercial standard for some parameters."
• Flagging Characteristics (Study 2): When a DIFF flag was triggered, the ground truth was established by expert consensus (averaged manual differential count) performed by three different technologists.

8. The Sample Size for the Training Set

• The document does not specify a separate training set or its sample size. The description of "linearity" suggests internal calibration and setting of parameters, but not a distinct, external training dataset in the context of machine learning. The EXCELL 22 is described as deriving its design from existing, proven instruments, implying its "training" or development would have been based on established hematology principles and previous generations of analyzers rather than a machine learning training dataset.

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

• As no explicit training set is mentioned in the context of machine learning, this information is not provided. The device's "training" would be tied to its design being "derived from the proven Danam DATACELL 18MS" and its WBC differential technology being "closely related to the technology utilized by the Cell-Dyn 3000." These predicate devices inherently embody prior knowledge and established methods as their "ground truth."

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