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· to determine the change in PCT level over time as an aid in assessing the cumulative 28-day risk of all-cause mortality for patients diagnosed with severe sepsis or septic shock in the ICU or when obtained in the emergency department or other medical wards prior to ICU admission,

· to aid in decision making on antibiotic therapy, for inpatients in the emergency department with suspected or confirmed lower respiratory tract infections (LRT) - defined as community-acquired pneumonia (CAP), acute bronchitis, and acute exacerbation of chronic obstructive pulmonary disease (AECOPD),

· to aid in decision making on antibiotic discontinuation for patients with suspected or confirmed sepsis.

Device Description

The Elecsys BRAHMS PCT assay is a two-step sandwich immunoassay with streptavidin microparticles, biotinylated antibody and antibody labeled with ruthenium as well as an electrochemiluminescence detection system. Procalcitonin (PCT) in the sample reacts with these labeled antibodies to form a sandwich complex. This complex binds to streptavidin coated magnetic microparticles, which are magnetically captured onto an electrode. Application of voltage to the electrode induces chemiluminescence which is measured by a photomultiplier tube. Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent barcode. An optional Procalcitonin CalCheck product is also available.

AI/ML Overview

The provided text describes the performance evaluation of the Elecsys BRAHMS PCT device. Here's a breakdown of the acceptance criteria and study details based on the information provided:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" for all performance parameters in a singular table. However, it presents claims and then demonstrates performance against those claims, implying these are the acceptance criteria.

Performance Characteristic	Acceptance Criteria (Implied from claims)	Reported Device Performance and Remarks
Precision	Not explicitly stated with numerical values, but implies acceptable within-run and intermediate precision. Expects reasonable %CV and % Total Error.	Repeatability (Within Run CV%): Ranges from 1.0% to 13.2% across different PCT concentrations. Intermediate Precision (Within Lab CV%): Ranges from 3.1% to 16.1% across different PCT concentrations. % Total Error: Ranges from 7.38% to 39.9% across different PCT concentrations. (Calculated using TE = 1.65 * CV + %bias, with %CV taken from intermediate precision).
Sample Matrix Comparison	Values obtained from different sample types (serum, Li-Heparin, K2-EDTA, K3-EDTA plasma) should be comparable.	Data evaluated using Passing/Bablok regression analysis; curves for method comparison are shown, but specific numeric agreement or non-inferiority limits are not explicitly stated in this section.
Endogenous Interferences	Recovery should be within ±15% of the initial value for PCT concentrations > 0.1 ng/mL, and within 0.015 ng/mL for concentrations 96% total agreement between the Elecsys BRAHMS PCT and the predicate device at the medical decision points 0.1, 0.25, 0.5 and 2.0 ng/mL. Regression slopes within +/- 10% of identity in Passing-Bablok and Weighted Deming Analysis.	Total Agreement: 0.1 ng/mL: 98.4% 0.25 ng/mL: 98.6% 0.5 ng/mL: 99.2% 2.0 ng/mL: 99.0% All met the >96% criteria. Passing Bablok Slope: 0.990 (95% CI: 0.984; 0.994) – within +/- 10% of 1. Weighted Deming Slope: 0.969 (95% CI: 0.963; 0.975) – within +/- 10% of 1. Pearson Correlation Coefficient: 1.000 for both.

2. Sample Size and Data Provenance for Test Set

Precision: Seven (7) human serum samples and two (2) QC samples.
Sample Matrix Comparison: A minimum of 40 serum/plasma pairs per sample material (serum, Li-Heparin plasma, K2-EDTA plasma, K3-EDTA plasma).
Endogenous Interferences: Spiked serum pools.
Exogenous Interferences (Drugs): Two human serum samples, spiked.
Analytical Specificity/Cross-reactivity: Native human serum samples, spiked.
Reagent On-Board Stability: Eight (8) human serum (HS) sample pools.
Calibration Stability: Fourteen (14) human serum samples.
LoQ: Seven native human serum (HS) samples. Total of 150 measuring points collected (7 samples measured in five-fold determination for each of 5 days).
Clinical Performance Evaluation (Method Comparison to Predicate): 496 native human clinical samples.
Data Provenance: The document states "human serum" and "human clinical samples" without specifying the country of origin. The assays are for "in vitro quantitative determination" using patient samples, implying retrospective collection for these performance studies.

3. Number of Experts and Qualifications for Ground Truth

This information is not provided in the document. The studies primarily involve analytical performance and method comparison against a predicate device and established laboratory guidelines rather than clinical interpretation by experts for ground truth establishment.

4. Adjudication Method for Test Set

This information is not applicable as the studies are analytical and method comparison, not involving expert adjudication of diagnostic outcomes or images.

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

This information is not provided and is not applicable. This device is an in-vitro diagnostic (IVD) assay that quantitatively measures procalcitonin levels, not an AI-assisted diagnostic imaging device requiring human reader interaction.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

This is an IVD assay, meaning its performance is inherently standalone (algorithm only, or rather, assay-only). The results are quantitative measurements. Human interpretation comes after the device generates the PCT value, in conjunction with other clinical assessments, as indicated in the "Indications for Use." The data presented here (e.g., precision, interference, method comparison) reflects the standalone analytical performance of the assay.

7. Type of Ground Truth Used

For precision, interference, stability, LoQ, and analytic specificity, the ground truth is based on known spiked concentrations or the reference value/measurement of the analyte in the samples.
For the method comparison study, the "ground truth" for comparison is the results obtained from the legally marketed predicate device (Elecsys BRAHMS PCT cleared under K173927). This establishes substantial equivalence.

8. Sample Size for the Training Set

This information is not provided. The document describes performance evaluation (testing) of the device. It does not detail the development or training process for the assay's reagents or calibration, which would involve a "training set." For an immunoassay, the "training" equivalent would typically involve assay development and optimization using various known samples and controls, rather than a distinct "training set" as understood in machine learning. Calibration data also serves a role similar to training in defining the dose-response curve.

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

This information is not provided as the document does not discuss a "training set" in the context of this IVD device. For an immunoassay, ground truth for development (e.g., calibrators) is typically established through careful gravimetric or volumetric preparations, reference methods, and standardization to an international reference material where available (as indicated by "This method has been standardized against the BRAHMS PCT LIA assay" and "Traceability/ Standardization").

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