(66 days)
The Cholestech LDX aspartate aminotransferase (AST) test is for the in vitro quantitative determination of AST in whole blood or serum on the Cholestech LDX Analyzer. AST measurements are used in the diagnosis and treatment of certain liver diseases (e.g., viral hepatitis and cirrhosis), and heart diseases.
The Cholestech LDX System combines enzymatic methodology and solid-phase technology to measure AST. Samples used for testing can be whole blood from a fingerstick (collected in a lithium heparin coated capillary tube), venous whole blood or serum. The sample is applied to a Cholestech LDX AST cassette. The cassette is then placed into the Cholestech LDX Analyzer where a unique system on the cassette separates the plasma from the blood cells. The plasma flows to both sides of the cassette and is transferred to the AST reaction pad. The Cholestech LDX Analyzer measures Aspartate aminotransferase by an enzymatic method based on the method formulation of Katsuyama et al. 12- Aspartic acid aminotransferase catalyzes the transfer of amino groups from L-Aspartic acid to alpha-Ketoglutarate producing oxaloacetate and glutamate. Oxaloacetate Decarboxylase converts the Oxaloacetate to Pyruvate by the removal of CO2. Pyruvate oxidase, in the presence of oxygen, oxidizes the pyruvate to acetylphosphate and hydrogen peroxide. In a reaction catalyzed by horseradish peroxidase, the peroxide reacts with an indicator dye to form a blue color at a rate proportional to the AST concentration of the sample. The resultant color in the reaction is measured by reflectance photometry. A brown magnetic stripe on each cassette contains the calibration required for the Cholestech LDX Analyzer to convert the reflectance reading to the AST concentration in U/L. 37°C.
The Cholestech LDX aspartate aminotransferase (AST) Test, a colorimetric assay for the determination of AST, has been found substantially equivalent to the Synchron CX® AST system. The device uses enzymatic methodology and solid-phase technology to measure AST in whole blood or serum.
1. Table of Acceptance Criteria and Reported Device Performance
The submission does not explicitly state pre-defined acceptance criteria with pass/fail thresholds for each performance metric. Instead, it presents performance data for accuracy, precision, and linearity, which are implicitly compared against the performance characteristics of the predicate device (Synchron CX® AST) and laboratory standards.
| Performance Metric | Acceptance Criteria (Implicit) | Reported Device Performance |
|---|---|---|
| Assay Range | Comparable to predicate device (5-400 U/L) and suitable for clinical use. | 10 – 400 U/L |
| Accuracy | Strong correlation and agreement with the predicate device for serum samples. Close agreement between different sample types (venous whole blood, fingerstick whole blood) and serum samples within the device itself. | LDX AST vs Synchron CX AST (Serum): n=109, slope=0.97, y-intercept=1.6, r=0.983 (Range 12–396 U/L) |
| LDX AST (Venous Whole Blood vs Serum): n=46, slope=1.08, y-intercept=0.3, r=0.998 (Range 13-343 U/L) | ||
| LDX AST (Fingerstick Whole Blood vs Serum): n=21, slope=0.86, y-intercept=4.4, r=0.934 (Range 13-65 U/L) | ||
| Precision | Acceptable variability (coefficient of variation, %CV) for clinical diagnostic purposes across different AST levels and sample types. | Low Control (~31 U/L): %CV = 8.8% |
| High Control (~106 U/L): %CV = 4.4% | ||
| Whole Blood Sample (58 U/L): %CV = 4.8% | ||
| Interference | Less than 10% interference from evaluated endogenous and exogenous substances. | Less than 10% interference when challenged by evaluated levels of substances |
| Hematocrit | Tolerance up to 50% hematocrit. | Up to 50% Hematocrit tolerance |
2. Sample Sizes Used for the Test Set and Data Provenance
- Accuracy (LDX AST vs. Synchron CX AST): 109 matched serum samples.
- Accuracy (LDX AST: Venous Whole Blood vs. Serum): 46 matched samples.
- Accuracy (LDX AST: Fingerstick Whole Blood vs. Serum): 21 matched samples.
- Precision: 2 levels of controls tested in duplicate, twice a day, over 20 days (80 replicates per level). One whole blood sample tested with the same protocol (80 replicates).
Data Provenance: The document does not specify the country of origin for the data or explicitly state whether the studies were retrospective or prospective. Given the nature of a 510(k) submission for a new device, it is highly likely that these were prospective studies conducted in a controlled environment as part of the device's validation. No specific patient demographics or disease states are detailed beyond the general "diagnosis and treatment of certain liver diseases (e.g., viral hepatitis and cirrhosis), and heart diseases."
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
N/A. This is an in vitro diagnostic device for quantitative determination of a biomarker (AST). The "ground truth" for the test set is established by comparative measurements against a legally marketed predicate device (Synchron CX® AST system) or by internal comparison to reference methods/sample types within the new device's system. It does not involve human expert interpretation of images or clinical assessments to establish a ground truth in the way medical imaging AI devices do. Therefore, no experts for ground truth establishment are applicable in this context.
4. Adjudication Method for the Test Set
N/A. This is not applicable as the test set involves quantitative measurements against a comparator device and internal comparisons, not subjective assessments requiring expert adjudication.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
N/A. This is an in vitro diagnostic device, not a medical imaging AI device requiring human reader interpretation or multi-reader studies. The device provides a quantitative measurement, and its effectiveness is determined by its analytical performance metrics (accuracy, precision, linearity) compared to established methods.
6. Standalone Performance Study
Yes, a standalone performance study was done in the sense that the Cholestech LDX AST device's performance was evaluated independently through precision studies, interference testing, hematocrit tolerance, and then compared to a predicate device (Synchron CX AST) as well as within its own system for different sample types. The reported accuracy metrics directly compare the LDX AST to the predicate and also compare results from various sample types processed by the LDX AST itself (venous whole blood, fingerstick whole blood vs. serum). This represents the algorithm's (device's) performance in generating the quantitative AST value.
7. Type of Ground Truth Used
The primary ground truth used for performance evaluation is comparative measurement against a legally marketed predicate device (Synchron CX® AST system) for accuracy. Additionally, internal comparisons of different sample types (venous whole blood, fingerstick whole blood) against serum samples measured by the same device serve as a verification of consistency and accuracy across intended sample matrices. The precision studies use control materials with known or established AST levels.
8. Sample Size for the Training Set
The document does not specify a separate training set or its sample size. For in vitro diagnostic (IVD) devices like this, the development process might involve initial experimentation and optimization, but the "training set" concept common in machine learning for image analysis or risk prediction is typically not directly applicable in the same way. Performance data presented relates to validation studies, not necessarily a distinct "training set" as understood in AI/ML contexts.
9. How the Ground Truth for the Training Set Was Established
N/A. As mentioned above, the concept of a "training set" with established ground truth as it applies to AI/ML is not explicitly detailed or typically relevant for this type of quantitative IVD submission in the same manner. The device's methodology is based on established enzymatic reactions, and its parameters would likely have been optimized during development rather than "trained" on a dataset with a defined ground truth in a machine learning sense.
§ 862.1100 Aspartate amino transferase (AST/SGOT) test system.
(a)
Identification. An aspartate amino transferase (AST/SGOT) test system is a device intended to measure the activity of the enzyme aspartate amino transferase (AST) (also known as a serum glutamic oxaloacetic transferase or SGOT) in serum and plasma. Aspartate amino transferase measurements are used in the diagnosis and treatment of certain types of liver and heart disease.(b)
Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 862.9.