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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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