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The Aptiva Celiac Disease IgG Reagent is an immunoassay utilizing particle-based multi-analyte technology for the semiquantitative determination of anti-tissue transglutaminase IgG autoantibodies and anti-deamidated gliadin peptide IgG autoantibodies in human serum. The presence of these antibodies, in conjunction with clinical findings and other laboratory tests, is an aid in the diagnosis of celiac disease and dermatitis herpetiformis, particularly in patients with selective IgA deficiency.

The Aptiva Celiac Disease IgG Reagent is intended for use with the Inova Diagnostics Aptiva System.

The Aptiva Celiac Disease IgG reagent utilizes particle based multi-analyte technology (PMAT) in a cartridge format. Each analyte (tissue transglutaminase [tTG] and deamidated gliadin peptide [DGP]) in the Aptiva Celiac Disease IgG reagent is a solid phase immunoassay utilizing fluorescent microparticles. This technology allows each of the two analytes, along with a human IgG capture antibody (IgG Control Microparticle), to be coated onto three uniquely recognizable paramagnetic microparticles, which are combined into one tube.

The Aptiva instrument is a fully automated, random access analyzer. This platform is a closed system with continuous load and random-access capabilities that processes the samples, runs the reagent and reports results. It includes liquid handling hardware, optical module (OM), and integrated computer with proprietary software and touch screen user interface.

The two analyte microparticles, along with the control microparticle, are stored in the reagent cartridge under conditions that preserve the proteins in their reactive states. When the assay cartridge is ready to be used for the first time, the reagent tube seals are pierced using the cartridge lid. The reagent cartridge is then loaded onto the Aptiva instrument, where the microparticles are automatically rehydrated using buffer located within the cartridge.

A patient's serum is diluted 1:23 with Aptiva system rinse by the instrument in a disposable cuvette. A small amount of the diluted sample is combined with assay buffer and the microparticle suspension in a second cuvette, and mixed (final serum dilution: 1:230). This reaction cuvette is incubated for 9 ½ minutes at 37°C. The cuvette is then exposed to a small magnet that holds the microparticles in place. The liquid is aspirated, and the microparticles are resuspended as system rinse is added to the cuvette and the magnet is removed. This wash cycle is repeated one more time. During the third wash, no system rinse is added after the aspiration step. After the third wash, phycoerythrin conjugated polyclonal anti-human lgG (known as PE Tracer IgG) is added to the microparticles in the cuvette, and mixed. Again, the cuvette is incubated for 9 ½ minutes at 37℃. Three wash steps, as described above, are performed on the microparticles. Following the wash steps, the microparticles are transferred to the of the instrument, where a charge coupled device (CCD) camera takes multiple images in order to identify and count the three unique microparticle regions, as well as determine the amount of conjugate on the microparticles. The control microparticle, a third particle, coated with goat anti-human IgG, is included in the reagent in as a control to flag low concentrations of IgG the patient serum sample as an assay verification step. The median fluorescent intensity (MFI) is proportional to the amount of PE Tracer that is bound to the human IgG, which is proportional to the amount of IgG antibodies bound to the corresponding microparticle regions.

For quantitation, the DGP IgG and tTG IgG assays (together as part of the Aptiva Celiac Disease IgG Reagent) each utilizes a predefined lot specific Master Curve that is uploaded onto the instrument through the reagent cartridge RFID tag. Every new lot of reagent cartridge must be calibrated before first use with the reagent specific calibrators. Based on the results obtained with the calibrators included in the Aptiva Celiac Disease IgG Calibrator kit (sold separately), an instrument specific Working Curve is created for each assay, which is used to calculate reported fluorescent light units (FLU) from the median fluorescent intensity (MFI) instrument signal obtained for each sample, on each of the two assays within the reagent.

Aptiva Celiac Disease IgG Calibrators and Aptiva Celiac Disease IgG Controls are sold separately.

The Aptiva Celiac Disease IgG Reagent kit contains the following materials:

One (1) Aptiva Celiac Disease IgG Reagent Cartridge, containing the following reagents for 200 determinations:

• a. Aptiva Celiac Disease IgG microparticle containing 3 unique microparticle regions coated with recombinant tissue transglutaminase, deamidated gliadin peptide, or goat antihuman IgG antibody.
• b. Assay buffer - colored pink, containing protein stabilizers and preservatives.
• C. PE Tracer IgG - phycoerythrin (PE) labeled anti-human IgG antibody, containing buffer, protein stabilizers and preservative.
• ð. Rehydration Buffer - containing protein stabilizers and preservatives.

This document describes the analytical and clinical performance of the Aptiva Celiac Disease IgG Reagent, an immunoassay for the semi-quantitative determination of anti-tissue transglutaminase IgG autoantibodies (tTG IgG) and anti-deamidated gliadin peptide IgG autoantibodies (DGP IgG) in human serum. This device is intended as an aid in the diagnosis of celiac disease and dermatitis herpetiformis.

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Acceptance Criteria and Reported Device Performance

The document presents several analytical performance characteristics and their corresponding acceptance criteria, along with the reported performance values. The primary clinical acceptance criteria are related to sensitivity and specificity, and the agreement with a predicate device.

2. Sample Sizes and Data Provenance

• Test Set (Clinical Validation Set): A total of 515 characterized samples.
  • 171 samples from celiac disease patients.
  • 20 samples from patients with IgA deficient celiac disease.
  • 34 dermatitis herpetiformis patients.
  • 290 control samples from patients with various types of autoimmune and infectious diseases.
• Data Provenance: The document does not explicitly state the country of origin. Given it's an FDA submission, it's typically a mix of US and possibly international data, but this is not specified. The studies are retrospective as they use "characterized samples" from a "cohort."
• Precision and Reproducibility Studies: Between 75 to 80 replicates per sample for repeatability/precision and reproducibility studies. These numbers are for analytical performance, not clinical.
• LoB, LoD, LoQ: 120 data points were generated for each assay on each reagent lot for LoB and LoD studies. For LoQ, 120 data points per assay per reagent lot.
• Linearity: The number of dilutions and duplicates used is stated (e.g., 4 human serum samples for DGP IgG and 3 for tTG IgG serially diluted, assayed in duplicates).
• Interference: 3 human serum specimens (one positive, one near cut-off, one negative) were tested for each assay.
• Sample Stability: 6 samples for DGP IgG, 7 for tTG IgG (tested in duplicates).
• Reagent Stability: 3 lots of microparticle beads and 3 lots of PE Tracer IgG for accelerated stability. Real-time stability data from 2 different lots.
• Reference Range/Cut-off Establishment:
  • Reference Population: 192 subjects from various autoimmune/infectious disease groups (e.g., Crohn's Disease, Autoimmune Thyroid Disease, Rheumatoid Arthritis).
  • Celiac Disease Patients: 11 diagnosed celiac disease (CD) patient specimens were assayed to aid in cut-off determination.
  • Apparently Healthy Donors (Expected Values): 120 blood donors.

3. Number of Experts and Qualifications

• The document does not mention the number of experts used to establish the ground truth for the test set, nor their specific qualifications. It refers to "characterized samples" and "diagnosed celiac disease (CD) patient specimens," implying a pre-existing clinical diagnosis, but the process of how these characterizations were definitively made (e.g., biopsy confirmation, clinical consensus, expert review) is not detailed for the test set.

4. Adjudication Method

• The document does not describe any specific adjudication method for the test set. The samples are described as "characterized," suggesting that their disease status was already established prior to their use in the study, likely through standard clinical diagnostic procedures, but no expert review or consensus process for this specific study's set is detailed.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• Not Applicable. This is an in-vitro diagnostic (IVD) device, specifically an immunoassay for determining autoantibodies in serum. MRMC studies are typically performed for imaging diagnostic devices (e.g., AI for radiology) where human readers (e.g., radiologists) interpret images with and without AI assistance. This document describes the performance of a lab test that outputs a quantitative result (FLU) and a qualitative interpretation (positive/negative) and does not involve human interpretation of complex data in the same way an imaging AI device would.

6. Standalone Performance

• Yes, standalone performance was done. The entire study report describes the standalone performance of the Aptiva Celiac Disease IgG Reagent without human intervention beyond performing the test and interpreting the quantitative results per the device's defined cut-offs. The sensitivity, specificity, and agreement with predicate devices are measures of its standalone performance.

7. Type of Ground Truth Used

• The ground truth for the clinical validation was based on clinical diagnosis/characterization of the patient samples.
  • For celiac disease and dermatitis herpetiformis patients, they were "diagnosed" or "characterized." While not explicitly stated, the gold standard for celiac disease diagnosis usually involves intestinal biopsy with characteristic changes, alongside clinical symptoms and serology.
  • For the control group, patients were characterized with "various types of autoimmune and infectious diseases," implying a clinical diagnosis for these conditions to confirm they are not celiac disease.
  • For the cut-off determination, "diagnosed celiac disease (CD) patient specimens" were used in conjunction with a reference population.

8. Sample Size for the Training Set

• The document does not specify a separate "training set" in the context of an AI/machine learning model. This device is an immunoassay, which relies on chemical reactions and optical detection, not on a machine learning algorithm trained on large datasets in the conventional sense. The "training" in this context refers to the development and optimization of the assay's reagents and parameters, and the establishment of master curves and cut-offs. The data used for calibration and master curve generation (e.g., "in-house Master Curve Standards with assigned FLU values run multiple times," "Calibrators included in the Aptiva Celiac Disease IgG Calibrator kit") effectively serve a similar purpose to training/calibration data in general analytical chemistry.

9. How Ground Truth for Training Set was Established

• Given this is an immunoassay, the concept of "ground truth" for a training set (as defined for AI/ML) is not directly applicable. Instead, the assay's performance and "ground truth" are established through:
  • Calibration: Using Master Curve Standards with "assigned FLU values" (likely determined through extensive in-house characterization and reference methods).
  • Controls: Using Aptiva Celiac Disease IgG Controls with "lot specific values assigned."
  • Reference Materials: The development of the assay's antigens (recombinant tTG and deamidated gliadin peptide) and antibodies would have involved rigorous characterization against known reference materials and clinical samples during the assay development stages to ensure they correctly bind to their target autoantibodies.
  • Cut-off determination: As mentioned in point 7, this involved a reference population of 192 subjects and 11 diagnosed celiac disease patients to establish the 5.00 FLU cut-off.

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