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Immunoassay for the in vitro quantitative determination of cortisol in human urine. The determination of cortisol is used for the recognition and treatment of functional disorders of the adrenal gland.

The electrochemiluminescence immunoassay "ECLIA" is intended for use on cobas e immunoassay analyzers.

The Elecsys Cortisol III immunoassay employs a competitive test principle using a cortisol-specific biotinylated monoclonal antibody and a cortisol-derivative labeled with a ruthenium complex. The Elecsys Cortisol III immunoassay is intended for the in vitro quantitative determination of cortisol in human urine. The determination of cortisol is used for the recognition and treatment of functional disorders of the adrenal gland on the cobas e immunoassay analyzers.

Results are determined via a calibration curve which is instrument-specifically generated by a two-point calibration and a master curve provided via the cobas link.

The Elecsys Cortisol III immunoassay reagent Rack Pack comprises the following:

M Streptavidin-coated microparticles (transparent cap), 1 bottle, 12.4 mL:
Streptavidin-coated microparticles 0.72 mg/mL; preservative.

R1 Anti-cortisol-Ab~biotin (gray cap), 1 bottle, 21.0 mL:
Biotinylated monoclonal anti-cortisol antibody (mouse) 18 ng/mL; danazol 20 μg/mL; MES buffer 100 mmol/L, pH 6.0; preservative.

R2 Cortisol-peptide~Ru(bpy) (black cap), 1 bottle, 21.0 mL:
Cortisol derivative (synthetic), labeled with ruthenium complex, 5 ng/mL; danazol 20 μg/mL; MES buffer 100 mmol/L, pH 6.0; preservative.

MES = 2-morpholino-ethane sulfonic acid

The provided 510(k) summary for the Elecsys Cortisol III device focuses primarily on non-clinical performance evaluations to demonstrate substantial equivalence to a predicate device. It does not describe a study to prove performance against specific acceptance criteria for diagnostic accuracy (e.g., sensitivity, specificity, or agreement with ground truth in a clinical context) with a test set of patient samples.

Here's an analysis of the available information:

1. Acceptance Criteria and Reported Device Performance

The document does not explicitly state "acceptance criteria" in the traditional sense for diagnostic performance metrics like sensitivity, specificity, or agreement against a clinical ground truth. Instead, it details performance specifications for various analytical aspects and states that these "met the predefined acceptance criteria." These are primarily related to the analytical performance of the assay itself.

2. Sample Size and Data Provenance for Test Set

• Precision (Repeatability & Intermediate Precision): Human urine samples (24-hour urine) and controls. Two replicates per run, two runs per day for 21 days for each of 4 human urine samples and 2 controls. (Total of $4 \text{ samples} \times 2 \text{ replicates/run} \times 2 \text{ runs/day} \times 21 \text{ days} = 336$ measurements for human urine, plus $2 \text{ controls} \times 2 \text{ replicates/run} \times 2 \text{ runs/day} \times 21 \text{ days} = 168$ measurements for controls. Or potentially 42 total runs for each sample/control).
• Analytical Sensitivity (LoB, LoD, LoQ): Not specified beyond "reagents and calibrators" likely being used.
• Linearity/Assay Reportable Range: Dilution series contained a minimum of 9 concentrations. Number of samples not explicitly stated but implies a set of samples specifically created to span the measuring range.
• HAMA: Not specified.
• Endogenous Interferences: Human urine samples (24-hour urine) were used. The number of samples is not explicitly stated.
• Analytical Specificity/Cross-Reactivity: Human urine (24-hour urine) samples. Specific numbers not provided beyond "samples were measured in the presence and absence of the potential cross-reactants."
• Exogenous Interferences – Drugs: In vitro tests performed on 12 commonly used pharmaceuticals and additional special drugs. This implies spiked samples rather than a "test set" of patient samples.
• Method Comparison: "Native 24 h urine samples" for comparison with the predicate device. The number of samples is not specified.
• Reference Range Study: Samples collected from an "apparently healthy population in the United States" across three study sites. The exact number of samples is not provided, but it's sufficient for establishing 2.5th and 97.5th percentiles (typically requires 120+ samples according to CLSI EP28-A3c).

Data Provenance: The document explicitly states "human urine samples (24-hour urine)" for most studies and for the reference range, "collected across three study sites... in the United States." This indicates prospective collection for the reference range study specifically for generating normal values applicable to the US population. For other analytical performance claims, the sample type (human urine) is generally mentioned, suggesting a similar provenance, likely for prospective testing within the manufacturer's lab or clinical sites.

3. Number of Experts and Qualifications for Ground Truth

Not applicable for the Elecsys Cortisol III. This is an in vitro diagnostic device (IVD) that quantitatively measures a biomarker (cortisol). The "ground truth" for such devices is typically established through recognized analytical standards, reference methods, and comparison to a legally marketed predicate device, rather than expert consensus on diagnostic images or clinical assessments. The closest to "ground truth" in this context would be the accuracy against a gold standard analytical method or purified cortisol standards. These details are not provided but are implicit in the validation that relies on CLSI guidelines.

4. Adjudication Method for the Test Set

Not applicable. As this is a quantitative IVD for a biomarker, diagnostic classification and adjudication by experts are not relevant to the described analytical studies. The performance is assessed by comparison to expected analytical results or a predicate device.

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

Not applicable. MRMC studies are typically for imaging devices or software that assist human readers in making a diagnosis. The Elecsys Cortisol III is an automated in vitro diagnostic immunoassay for quantitative measurement of cortisol in urine. It does not involve human readers interpreting cases with or without AI assistance.

6. Standalone Performance Study

Yes, the entire submission describes standalone performance. The Elecsys Cortisol III is an immunoassay designed to operate on cobas e immunoassay analyzers. All the performance data (precision, sensitivity, linearity, interference, cross-reactivity, method comparison) are generated directly from the device's measurement of cortisol in urine samples. The device itself performs the quantitative determination without human-in-the-loop interpretation impacting the measurement results. The method comparison study directly compares its quantitative output to the predicate device's quantitative output.

7. Type of Ground Truth Used

For an IVD like Elecsys Cortisol III, the "ground truth" for the test set is established by:

• Reference standards/Calibrators: For analytical sensitivity (LoB, LoD, LoQ) and linearity studies, known concentrations of cortisol (or materials traceable to them) are used.
• Predicate device comparison: For method comparison, the results from the Elecsys Cortisol III are compared to those obtained from the legally marketed ARCHITECT Cortisol (K062204), which serves as the established "truth" or benchmark for demonstrating substantial equivalence.
• Spiked samples/characterized samples: For interference and cross-reactivity studies, samples with known concentrations of interferents or cross-reactants are used to determine the device's accuracy in their presence.
• Clinically characterized healthy population samples: For the reference range study, samples from healthy individuals are used to establish normal ranges, though this isn't a "ground truth" for diagnostic accuracy.

8. Sample Size for the Training Set

The document does not mention "training set" in the context of an AI/ML algorithm. This device is an immunoassay, which relies on chemical reactions and optical detection, not an AI/ML model that requires a training set. The term "training set" is therefore not applicable here.

9. How the Ground Truth for the Training Set Was Established

Not applicable. As noted above, there is no AI/ML training set for this immunoassay device.

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