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For in vitro diagnostic use with the IMMULITE® 2000 Systems Analyzers — for the quantitative measurement of cortisol (hydrocortisone, Compound F) in serum, as an aid in the clinical assessment of adrenal status.

The IMMULITE 2000 Cortisol assay is comprised of the following components: Cortisol Bead Pack (solid phase) containing Polyclonal rabbit anti-cortisol antibody; Cortisol Reagent Wedge (liquid phase) containing Alkaline phosphatase (bovine calf intestine) conjugated to cortisol in buffer, with preservative; and Cortisol Adjustors (Low and High) containing Cortisol in processed human serum, with preservative.

The provided document describes the IMMULITE® 2000 Cortisol device, a chemiluminescence immunoassay for the quantitative measurement of cortisol in serum, used as an aid in the clinical assessment of adrenal status. This submission (K202826) is for a modified device due to a new supplier of the antibody, with the predicate device being the IMMULITE® 2000 Cortisol (K931409).

Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Executive Summary:

The study aims to demonstrate substantial equivalence of the modified IMMULITE® 2000 Cortisol assay to the predicate device. The performance characteristics evaluated included detection limits, linearity, precision, spike recovery, method comparison, and analysis of interfering and cross-reactive substances. All evaluated studies produced acceptable results compared to the predicate device.

1. Table of Acceptance Criteria and Reported Device Performance:

The document doesn't explicitly state "acceptance criteria" for each performance characteristic in a quantifiable manner (e.g., "linearity must have an R-squared > 0.98"). Instead, it states that the studies "produced acceptable results when compared to the Predicate device and were deemed verified" or that information "has not changed and are as per K931409." For method comparison, a regression equation and correlation coefficient are provided.

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

• Method Comparison:

  • Sample Size: 149 native patient samples.
  • Data Provenance: Not explicitly stated, but "native patient samples" implies clinical samples, likely from a hospital or lab. Retrospective or prospective is not specified. Country of origin not specified.

• Linearity:

  • Sample Size: Not explicitly stated as a number of unique patient samples, but 9 levels of dilutions were prepared from high and low human serum pools.
  • Data Provenance: Human serum pools. Retrospective or prospective, and country of origin are not specified.

• Specificity (Cross-Reactivity):

  • Sample Size: Not explicitly stated, but multiple cross-reactant solutions were prepared and spiked into "a blank sample (charcoal-adsorbed human serum)."
  • Data Provenance: Charcoal-adsorbed human serum.

• Interference:

  • Sample Size: 5 patient samples.
  • Data Provenance: Not explicitly stated, but "patient samples" implies clinical samples. Retrospective or prospective, and country of origin are not specified.

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

This information is not provided in the document. For in vitro diagnostic assays measuring specific analytes, the "ground truth" is typically the measured value itself, often established by a validated reference method or the predicate device, rather than expert interpretation of images or clinical findings.

4. Adjudication Method for the Test Set:

This is not applicable in the context of an in vitro diagnostic assay like this. Adjudication methods (e.g., 2+1, 3+1) are common in studies involving subjective assessments, such as imaging interpretation by multiple readers. For quantitative measurements, the "truth" is typically derived from the measurement itself.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, and the effect size of how much human readers improve with AI vs without AI assistance:

This is not applicable. The device is an in vitro diagnostic assay, not an AI or imaging device that assists human readers.

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

This is not applicable. The device is a laboratory instrument (IMMULITE® 2000 System Analyzers) that performs a chemiluminescent immunoassay. It does not involve a "standalone algorithm" in the same sense as an AI diagnostic software. Its performance is inherent to the assay and instrument.

7. The Type of Ground Truth Used:

For this type of in vitro diagnostic device, the "ground truth" is established by:

• Reference Methods/Predicate Device: For method comparison, the "truth" is implicitly the values obtained from the predicate device (unmodified IMMULITE® 2000 Cortisol assay).
• Known Concentrations: For linearity, detection limits, specificity, and interference studies, the "ground truth" is based on precisely prepared samples with known concentrations of cortisol, cross-reactants, or interferents, or "spiked" samples where the added amount is known. These are often prepared from certified reference materials or highly pure substances.

8. The Sample Size for the Training Set:

This is not applicable. This is an immunoassay device, not a machine learning or AI model that requires a "training set" in the conventional sense. The development and optimization of the assay chemistry, reagents, and instrument operation are based on laboratory experiments and validation processes, not data training.

9. How the Ground Truth for the Training Set was Established:

This is not applicable as there is no "training set" for this type of device. The accuracy of the assay is established through extensive analytical validation using prepared controls, reference materials, and patient samples compared against established methods.

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For in vitro diagnostic use with the IMMULITE® and IMMULITE 1000 Analyzers - for the quantitative measurement of cortisol (hydrocortisone, Compound F) in serum, as an aid in the clinical assessment of adrenal status.

The IMMULITE/IMMULITE® 1000 Cortisol assay is comprised of the following components: Cortisol Test Unit (solid phase) - 1 bead/Test unit, Polyclonal rabbit anti-cortisol antibody. Cortisol Reagent Wedge (liquid phase) - 7.5 mL, Alkaline phosphatase (bovine calf intestine) conjugated to cortisol in buffer, with preservative. Cortisol Adjustors (Low and High) - 3 mL, Cortisol in processed human serum, with preservative.

The document describes the performance characteristics of the IMMULITE/IMMULITE® 1000 Cortisol assay, which is an in vitro diagnostic device. This device measures cortisol in serum to aid in the clinical assessment of adrenal status. The submission is for a modified device with a new supplier for the antibody, maintaining the same intended use.

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

1. A table of acceptance criteria and the reported device performance:

The document doesn't explicitly present a table labeled "acceptance criteria." Instead, it describes performance characteristics that were evaluated to demonstrate substantial equivalence to a predicate device. The implied acceptance criterion for each characteristic is that the performance of the modified device should be comparable to or within acceptable limits of the predicate device, or meet established clinical laboratory standards (e.g., CLSI guidelines).

Here's a table based on the provided "Performance Characteristics" section, showing the evaluated parameters and their reported outcomes:

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

• Detection Limits (LoB, LoD, LoQ): The sample sizes are not explicitly stated for the determination of LoB, LoD, and LoQ, but these are typically determined using multiple replicates of blank and low-concentration samples. The study was conducted in accordance with CLSI EP17-A2.
• Linearity: The study involved combining a high human serum pool with a low human serum pool to create 9 levels of dilutions. The number of individual samples within these pools is not specified. The provenance is "human serum."
• Method Comparison:
  • Sample Size: A total of 152 native patient samples.
  • Data Provenance: "native patient samples," indicating human origin. The country of origin is not specified, but the applicant's address is in the UK. The study was retrospective or prospective is not explicitly stated, but "patient samples" typically implies retrospectively collected samples for this type of comparison study.

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

This is an in vitro diagnostic (IVD) assay measuring a biomarker (cortisol). The "ground truth" for such devices is established by reference methods or validated higher-order methods, not typically by expert human interpretation (like in imaging AI).

• For Method Comparison, the ground truth is simply the measurement obtained from the predicate device (unmodified IMMULITE 1000 Cortisol Assay), which is presumed to be the accepted standard. No human experts are used for ground truth establishment in this context.
• For Detection Limits, Linearity, Specificity, and Interference, the ground truth is based on the precise preparation of known concentrations of analytes, cross-reactants, or interfering substances, and comparison to the assay's ability to accurately measure them. This does not involve expert human interpretation.

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

Not applicable. As an IVD assay measuring a quantitative biomarker, adjudication by human experts is not part of the ground truth establishment or performance evaluation process. The measurements are objective.

5. 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 not an AI-assisted diagnostic imaging device for human interpretation, but rather an automated in vitro diagnostic assay measuring a chemical compound. Therefore, MRMC studies are not relevant.

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

Yes, the performance characteristics described are indeed standalone performance of the device (IMMULITE/IMMULITE® 1000 Cortisol assay) itself. It evaluates the accuracy, precision, limits, and specificity of the biochemical measurement system, without human involvement in the direct measurement or interpretation of the assay's output for diagnostic purposes in the study. The human role is in operating the instrument and interpreting the numerical result in the clinical context, but the study focuses on the analytical performance of the device.

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

The ground truth used for this IVD device is primarily:

• Reference measurements/Predicate device measurements: For the method comparison study, the measurements from the legally marketed predicate device (IMMULITE/IMMULITE® 1000 Cortisol, K931409) serve as the reference or "ground truth" for comparison.
• Prepared known concentrations: For studies like linearity, detection limits, specificity (cross-reactivity), and interference, the ground truth is established by preparing samples with precisely known concentrations of the analyte, cross-reactants, or interfering substances.
• Standardized methods/guidelines: Compliance with CLSI (Clinical and Laboratory Standards Institute) guidelines (e.g., EP17-A2, EP06-A, EP09c, EP07) implies that the ground truth methodology follows accepted laboratory standards for analytical performance.

8. The sample size for the training set:

Not applicable. This document describes a traditional in vitro diagnostic immunoassay, not a machine learning or artificial intelligence algorithm that requires a "training set." The development of such assays involves chemical and biological optimization, not data-driven model 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.

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