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The ARCHITECT Tacrolimus assay is a chemiluminescent Microparticle immunoassay (CMIA) for the quantitative determination of tacrolimus in human whole blood on the ARCHITECT i System. The ARCHITECT Tacrolimus assay is to be used as an aid in the management of liver and kidney allograft patients receiving tacrolimus therapy.

The ARCHITECT Tacrolimus Calibrators are for the calibration of the ARCHITECT i System when used for the quantitative determination of tacrolimus in human whole blood.

The ARCHITECT Tacrolimus Whole Blood Precipitation Reagent is for the extraction of tacrolimus from samples (human whole blood patient specimens, controls, and ARCHITECT Tacrolimus Calibrators) to be tested on the ARCHITECT i System.

The ARCHITECT Tacrolimus assay is a delayed one-step immunoassay for the quantitative determination of tacrolimus in human whole blood using CMIA technology with flexible assay protocols, referred to as Chemiflex.

Prior to the initiation of the automated ARCHITECT sequence, a manual pretreatment step is performed in which the whole blood sample is extracted with a precipitation reagent and centrifyged. The supernatant is decanted into a Transplant Pretreatment Tube, which is placed onto the ARCHITECT i System.

Sample, assay diluent, and anti-tacrolimus coated paramagnetic microparticles are combined to create a reaction mixture. Tacrolimus present in the sample binds to the anti-tacrolimus coated microparticles. After a delay, tacrolimus acridinium-labeled conjugate is added to the reaction mixture. The tacrolimus on the acridinium-labeled conjugate competes for the available binding sites on the microparticles. Following an incubation, the microparticles are washed, and pretrigger and trigger solutions are added to the reaction mixture. The resulting chemiluminescent reaction is measured as relative light units (RLUs).

An indirect relationship exists between the amount of tacrolimus in the RLUs detected by the ARCHITECT i System optics.

Here's a summary of the acceptance criteria and the study details for the ARCHITECT Tacrolimus assay, based on the provided 510(k) summary:

Acceptance Criteria and Device Performance

This document primarily describes performance characteristics rather than explicit acceptance criteria with defined pass/fail thresholds against which the reported performance is compared. However, the reported performance values implicitly define the level of performance deemed acceptable by the manufacturer for substantial equivalence.

Study Details

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

   • Method Comparison (vs. IMx Tacrolimus II):
     • Number of Observations: 124 human whole blood specimens.
     • Provenance: From renal and liver transplant patients receiving tacrolimus therapy (retrospective/prospective not explicitly stated, but the "patients receiving tacrolimus therapy" suggests real-world clinical samples). Country of origin is not specified.
   • Method Comparison (vs. LC/MS/MS):
     • Number of Observations: 125 human whole blood specimens.
     • Provenance: The text states "Additional testing of the above sample was completed with LC/MS/MS," implying these were likely the same or a very similar set of clinical samples as used for the IMx comparison. Country of origin not specified.
   • Precision: Not explicitly stated as a "test set" and rather uses "Abbott Immunosuppressent-MCC (levels 1, 2, and 3) and five whole blood panels".
   • Linearity: Not explicitly stated as a "test set" sample size beyond "high concentration tacrolimus whole blood specimens."
   • Functional Sensitivity: Not explicitly stated as a "test set" sample size beyond "Whole blood specimens were spiked with tacrolimus."
   • Analytical Sensitivity: n=24 runs, 10 replicates for calibrator A, 4 replicates for calibrator B.
   • Interference: "Whole blood specimens were supplemented with various drugs and potentially interfering compounds." Specific sample size not given.
   • Specificity: "Aliquots of whole blood specimens" augmented with tacrolimus, 5 specimens spiked with cross-reactant solution for each metabolite.

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

   • The document does not mention the use of human experts to establish ground truth. Instead, it compares the device's performance against a predicate device (IMx Tacrolimus II assay) and a reference method (LC/MS/MS).

3. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

   • Not applicable as the ground truth was established by comparison to other analytical methods (IMx and LC/MS/MS), not by expert adjudication of cases.

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:

   • Not applicable. This is an in vitro diagnostic (IVD) device for quantitative determination of a drug in whole blood, not an imaging device requiring human reader interpretation or AI assistance.

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

   • Yes, the performance characteristics (Precision, Linearity, Functional Sensitivity, Analytical Sensitivity, Interference, Specificity) and method comparison studies (against IMx and LC/MS/MS) describe the standalone performance of the ARCHITECT Tacrolimus assay system itself, without human interpretation in the results generation. The human interaction is limited to the manual pretreatment step and placing the sample on the system.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

   • Reference Method Comparison: The ground truth for the method comparison studies was established by:
     • Comparison to an existing, legally marketed predicate device: ABBOTT IMx® Tacrolimus II Microparticle Enzyme Immunoassay.
     • Comparison to a gold standard analytical method: LC/MS/MS (Liquid Chromatography-Tandem Mass Spectrometry).
   • For other performance characteristics (Precision, Linearity, Functional Sensitivity, Analytical Sensitivity, Interference, Specificity), the ground truth was implicitly defined by the known concentrations in spiked or controlled samples, or by established analytical methods for assessing these parameters.

7. The sample size for the training set:

   • The document does not explicitly mention a "training set" in the context of machine learning or AI models. This device is an immunoassay (CMIA), which typically relies on established chemical and biological reactions and calibration curves rather than an AI model requiring a distinct training phase with a labeled dataset in the same way an imaging AI might. The development and validation of the assay reagents and protocols would involve extensive internal testing and optimization, but this is not typically referred to as a "training set" in the context of this device type.

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

   • As there's no explicit "training set" for an AI/machine learning model described, this question is not fully applicable. However, for the development of the assay, the "ground truth" (i.e., accurate tacrolimus concentrations) would have been established through highly analytical methods such as LC/MS/MS or gravimetric preparation of standards to develop and validate the calibrators and control materials used throughout the assay's development.

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