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Sigma Diagnostics INFINITY™ AST Reagent is intended for the in vitro quantitative determination of AST (Aspartate Aminotransferase EC2.6.1.1) in human serum and plasma on both automated and manual systems.

The Sigma Diagnostics INFINITY AST Reagent is based on the recommendations of the IFCC. The series of reactions involved in the assay system is as follows:

1. AST present in the sample catalyzes the transfer of the amino group from L-aspartate to 2-oxoglutarate forming oxaloacetate and L-glutamate.
2. Oxaloacetate in the presence of NADH and Malate dehydrogenase (MDH), is reduced to L-malate. In this reaction NADH is oxidized to NAD. The reaction is monitored by measuring the rate of decrease in absorbance at 340 nm due to the oxidation of NADH to NAD.
3. Addition of Lactate dehydrogenase (LDH) to the reagent is necessary to achieve rapid and complete reduction of endogenous pyruvate so that it does not interfere with the assay.

The provided text describes the Sigma Diagnostics INFINITY™ AST Reagent, intended for the quantitative determination of AST in human serum and plasma. The study presented is primarily a correlation study to demonstrate substantial equivalence to a previously cleared device, not a typical diagnostic efficacy study with acceptance criteria like sensitivity or specificity.

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Acceptance Criteria and Device Performance Study

The primary study presented demonstrates the substantial equivalence of the INFINITY™ AST Reagent to an existing Sigma Diagnostics AST Reagent (Procedure No. 58, K954839) via a correlation study, rather than setting distinct acceptance criteria for diagnostic accuracy metrics.

1. Table of Acceptance Criteria and Reported Device Performance

Explanation of Performance: The regression equation INFINITY AST = 0.98 (AST 58) + 0.6 with N=126 suggests a strong correlation between the new INFINITY AST Reagent and the predicate AST 58 Reagent. A slope of 0.98 is very close to 1, and an intercept of 0.6 is very close to 0, indicating that the new reagent provides results highly consistent with the established predicate device. This is the primary evidence of "performance" for a substantial equivalence claim in this context.

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

• Sample Size: N = 126 plasma samples.
• Data Provenance: The text does not explicitly state the country of origin. It is a retrospective study, as it involved analyzing a set of samples and comparing results with a previously cleared device.

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

• Not Applicable. This is an in vitro diagnostic (IVD) assay where the "ground truth" for the test set is established by the predicate device's measured values, which are chemical concentrations, not interpretations by human experts.

4. Adjudication Method for the Test Set

• Not Applicable. As this is a correlation study comparing results of two chemical assays, there is no expert adjudication method used. The comparison is purely quantitative.

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

• No. This is an in vitro reagent, not a device that involves human readers interpreting cases. Therefore, an MRMC study is not applicable.

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

• Yes, effectively. The study described is a standalone performance assessment of the reagent's ability to measure AST levels. While the measurement process involves laboratory personnel, the performance evaluation itself focuses on the reagent's output against a reference (the predicate device's output), independent of human interpretation or intervention in the diagnostic decision-making process beyond performing the assay.

7. The Type of Ground Truth Used

• Predicate device's measured values. The "ground truth" in this context is the AST concentration determined by the previously cleared Sigma Diagnostics AST Reagent, Procedure No. 58 (K954839), which serves as the comparator or reference method for demonstrating equivalence.

8. The Sample Size for the Training Set

• Not Applicable. This is a chemical reagent and not a machine learning or AI algorithm that requires a training set. The "design" of the reagent is based on established biochemical principles (IFCC recommendations) rather than data-driven training.

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

• Not Applicable. As there is no training set for this type of device, this question is not relevant.

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