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The DIGXN method is an in vitro diagnostic test for the quantitative measurement of digoxin in human serum and plasma on the Dimension Vista® System. Measurements of digoxin are used in the diagnosis and treatment of digoxin overdose and in monitoring levels of digoxin to help ensure appropriate therapy.

The DRUG 4 CAL is an in vitro diagnostic product for the calibration of the LOCI Digoxin (DIGXN) method on the Dimension Vista® System.

Method: The DIGXN method is a homogeneous, sequential, chemiluminescent immunoassay based on LOCI® technology. The LOCI® reagents include two synthetic bead reagents and a biotinylated F(ab')2 fragment of an anti-Digoxin mouse monoclonal antibody. The first bead reagent (Chemibeads) is coated with ouabain, a weaker binding analog of digoxin, and contains a photosensitizer dye. In a first step, sample is incubated with biotinylated F(ab')> which allows digoxin from the sample to saturate a fraction of the biotinylated F(ab')2 that is directly related to the digoxin concentration. In a second step, ouabain chemibeads are added and form bead/biotinylated F(ab')> immunocomplexes with the non-saturated fraction of the biotinylated F(ab')>. Sensibeads are then added and bind to the biotin to form bead pair immunocomplexes. Illumination of the complex at 680 nm generates singlet oxygen from Sensibeads which diffuses into the Chemibeads, triggering a chemilyminescent reaction. The resulting signal is measured at 612 nm and is an inverse function of the digoxin concentration in the sample.

Calibrator: The DRUG 4 Calibrator is a 5 level, liquid calibrator. It is packaged as a kit of ten vials, two vials per level (A, B, C, D and E), 2.5 mL per vial. The product matrix is human serum.

Here's a summary of the acceptance criteria and study details for the Dimension Vista® LOCI Digoxin Flex® Reagent Cartridge (K6435) and Dimension Vista® DRUG 4 Calibrator (KC460), based on the provided text:

Acceptance Criteria and Device Performance

Study Details

1. Sample size used for the test set and the data provenance:

   • Test Set Sample Size: 116 samples for the method comparison study.
   • Data Provenance: Not specified in the provided text (e.g., country of origin, retrospective or prospective).

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • This is a diagnostic device for measuring a chemical analyte (digoxin concentration). The "ground truth" for the test set refers to the values obtained from the predicate device. Therefore, human experts are not directly establishing a subjective ground truth, but rather running the predicate device. The qualifications of the technicians or operators running these instruments are not specified.

3. Adjudication method for the test set:

   • Not applicable. The comparison is between two quantitative assays (the new device and the predicate device), not involving human interpretation requiring adjudication.

4. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • No. This is an in vitro diagnostic device for measuring an analyte, not an AI-assisted diagnostic imaging or interpretation tool for human readers.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

   • Yes, the performance stated is for the device (DIGXN method) operating in a standalone capacity, producing quantitative measurements of digoxin concentration. The results were then compared to those of the predicate device.

6. The type of ground truth used:

   • The "ground truth" for the method comparison was the quantitative results obtained from the predicate device (Dimension® Digoxin Flex® reagent cartridge, DGNA). For reproducibility, the "ground truth" is inherent to the statistical analysis of repetitive measurements, aiming to quantify the device's inherent variability around a mean value for known control materials and serum pools.

7. The sample size for the training set:

   • Not applicable as this is not an AI/machine learning device that requires a training set in that sense. The device's calibration and validation would involve various samples, but they are not referred to as a "training set" in the context of this traditional analytical device. The calibration for the DIGXN method uses the DRUG 4 Calibrator, which has five levels.

8. How the ground truth for the training set was established:

   • Not applicable as there is no "training set" in the context of AI. For the calibrator, the "ground truth" (assigned values for each of the five levels) would have been established during its manufacturing and validation process, ensuring accuracy and traceability, likely against reference methods or materials, though this detail is not provided in the summary.

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