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ACE® Phenytoin Reagent is intended for use in the quantitative determination of phenytoin in human serum.
ACE® Phenytoin Reagent is intended for the quantitative determination of phenytoin in serum using the ACE® clinical chemistry analyzer.
Phenytoin is one of the most widely prescribed anti-convulsant drugs for the treatment of epilepsy, particulary grand mal epilepsy (major motor), corticol focal seizures and temporal lobe epilepsy.

The ACE® Phenytoin Reagent contains two reagents, an Antibody/Substrate reagent and an Enzyme Conjugate reagent. The assay uses specific antibodies to phenytoin and is based on the competition of an enzyme glucose-o-phosphate dehydrogenase (G6PDH) labeled drug and the free drug from the sample, for a fixed amount of specific antibody binding sites. In the absence of free drug from the sample, the drug-labeled G6PDH is bound by the specific antibody and the enzyme activity is inhibited. This phenomenon creates a relationship between drug concentration in the sample and the enzyme activity. The enzyme G6PDH activity is determined bichromatically on the ACE® at 340/505 nm by measuring its ability to convert NAD* to NADH.

The provided document describes the ACE® Phenytoin Reagent, an enzyme immunoassay for the quantitative determination of phenytoin in human serum, and its substantial equivalence to a predicate device.

Here's an analysis of the acceptance criteria and study data:

1. Table of Acceptance Criteria and Reported Device Performance

The submission relies on demonstrating substantial equivalence to a predicate device (Diagnostic Reagents, Inc. (DRI) - Phenytoin Reagent [510(k) Number K945725]). The performance parameters below are compared between the proposed device and the predicate device, implying that the predicate's performance serves as the de-facto acceptance criteria for the proposed device to be considered substantially equivalent.

Note on Acceptance Criteria: The document states, "Based on these data, the Schiapparelli Biosystems ACE® Phenytoin Reagent is substantially equivalent to the predicate device." This implies that the observed performance of the proposed device was deemed sufficiently similar or better than the predicate's performance to meet the regulatory standard of substantial equivalence. While some metrics for the proposed device (e.g., %CV for precision) are numerically higher than the predicate, the overall comparison including the strong correlation coefficient (0.993) was sufficient for clearance. Specific numerical acceptance cut-offs are not explicitly stated, but are inferred from the predicate's performance and the FDA's clearance decision.

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

• Correlation Study: The proposed device's correlation study involved a sample size (N) of 49.
• Provenance: The document does not explicitly state the country of origin or whether the data was retrospective or prospective. Given the context of a 510(k) submission for a clinical chemistry reagent, test samples would typically be human serum and would have been collected in a setting relevant to clinical diagnostics, likely within the United States where the company is based.

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

• This type of in vitro diagnostic device (IVD) for quantitative analyte measurement (phenytoin) does not typically rely on "expert ground truth" in the same way an imaging or pathology device would.
• The "ground truth" for the correlation study is established by a reference method or a standardized clinical analyzer. In this case, the proposed device's results were correlated against the Hitachi 717, which is a widely used and established clinical chemistry analyzer. The Hitachi 717's results are considered the comparative "truth" for the study.
• Therefore, the concept of "number of experts" and "qualifications of experts" for ground truth establishment is not directly applicable here.

4. Adjudication Method for the Test Set

• Adjudication methods (e.g., 2+1, 3+1) are typically used for subjective assessments where expert readers' interpretations need to be reconciled, such as in imaging studies.
• For quantitative IVDs like this one, the "adjudication" is inherent in the performance of the reference method (Hitachi 717). There isn't an external adjudication process for reconciling conflicting quantitative readings of phenytoin concentrations because the reference method provides a single, accepted value for each sample.

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

• No, an MRMC comparative effectiveness study was not done.
• MRMC studies are specific to evaluating the diagnostic performance of devices (often imaging) where human readers interpret cases, and the study aims to quantify the improvement in reader performance (e.g., accuracy, sensitivity, specificity) with aid from the AI device versus without.
• This device is an automated clinical chemistry reagent, not an AI-powered diagnostic imaging tool that assists human readers. Its performance is measured directly by its analytical accuracy, precision, and correlation with established methods.

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

• Yes, the performance assessment described is inherently a standalone evaluation.
• The ACE® Phenytoin Reagent, when used on the ACE® clinical chemistry analyzer, operates as an automated system. The reported precision (within-run, between-run) and correlation data reflect the performance of the reagent and analyzer system without direct human intervention in the result generation beyond sample loading and instrument operation.
• The "algorithm" here refers to the enzyme immunoassay methodology itself and the instrument's data processing, which operates without human interpretation of the primary reaction.

7. The Type of Ground Truth Used

• The ground truth used for the performance assessment, specifically the correlation study, was based on measurements from an established and validated clinical chemistry analyzer, the Hitachi 717. This serves as a "comparator method" ground truth.
• For precision studies, ground truth is inferred by the statistical properties of repeated measurements on known concentrations or quality control materials.

8. The Sample Size for the Training Set

• The document does not provide information on a "training set" sample size.
• This is expected for an immunoassay reagent. Immunoassays are based on biochemical principles and do not typically involve machine learning algorithms that require a separate "training set" for model development in the way AI/ML devices do. The assay performance is inherent in the reagent formulation and reaction kinetics.
• Any internal development or optimization prior to validation would use development samples, but these are distinct from a machine learning "training set".

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

• As there is no mention of a "training set" in the context of machine learning, the question of how its ground truth was established is not applicable to this device.
• The "ground truth" for developing and optimizing such a reagent would implicitly be the accurate measurement of phenytoin in samples using highly reliable, perhaps gold-standard, analytical methods (e.g., LC-MS/MS or other established clinical analyzers) to ensure the reagent accurately reflects phenytoin concentrations. However, this is part of chemical development, not statistical machine learning training.

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