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K-ASSAY® CRP (Ver.2) is intended to be used for the quantitative determination of C-reactive protein (CRP) in human serum and plasma (potassium-EDTA or lithium-heparin) by immunoturbidimetric assay. Measurement of CRP aids in the detection and evaluation of infection, tissue injury, inflammatory disorders and associated diseases. FOR IN VITRO DIAGNOSTIC USE.

The K-ASSAY® CRP (Ver.2) assay quantifies C-reactive protein based on immunoturbidimetric assay. The reagent uses latex combined with goat polyclonal antibody specific to human CRP. By adsorbing CRP in the sample to the surface of the latex particles and reacting it with the anti-CRP antibody, specific aggregation corresponding to the CRP concentration occurs. Since the absorbance of the reaction changes in proportion to the amount of aggregation, the concentration of CRP in the sample is determined based on the calibration curve prepared using a standard of known CRP concentrations. The K-ASSAY® CRP (Ver.2) assay can be run using a chemistry analyzer. 6 levels of calibrators from the K-ASSAY® CRP Calibrator (Ver.2) calibrators are used for quantifying the levels of CRP present in the patient's sample.

This document describes the FDA 510(k) clearance for the K-ASSAY CRP (Ver.2) IVD device. This device is an in-vitro diagnostic test system, which means it analyzes biological samples in a lab setting rather than directly interacting with a patient.

Therefore, the concepts of "human readers," "AI assistance," "effect size," "multi reader multi case (MRMC) comparative effectiveness study," and "standalone (i.e. algorithm only without human-in-the loop performance)" are not applicable in this context. These terms are typically used for medical imaging AI/ML devices where human interpretation is involved.

For this in-vitro diagnostic device, the "acceptance criteria" and "study that proves the device meets the acceptance criteria" are related to its analytical performance characteristics when compared to a predicate device, and the reported device performance refers to the results of these analytical studies.

Here's the breakdown of the information provided within the scope of this IVD device:

1. Table of Acceptance Criteria and Reported Device Performance

For an IVD device like the K-ASSAY® CRP (Ver.2), the acceptance criteria are generally established by demonstrating equivalent or superior analytical performance compared to a legally marketed predicate device, and meeting established CLSI guidelines for accuracy, precision, linearity, and interference. The "reported device performance" refers to the actual study results for these characteristics.

• Within-Run CV: 0.8% to 2.2%
• Between-Run CV: 0.0% to 0.6%
• Within-Lot CV: 0.9% to 1.9%
• Between-Lot CV: 0.0% to 1.2%
• Total CV: 0.9% to 2.3%
  Multisite Precision (Combined Data From 3 Analyzers):
• Repeatability CV: 0.5% to 1.5%
• Between-Run CV: 0.0% to 1.1%
• Between-Day CV: 0.6% to 1.8%
• Between-Site CV: 0.9% to 1.8%
• Reproducibility CV: 1.1% to 2.5% |
  | Interference: No significant interference from common endogenous and exogenous substances (recovery within 10% of initial value). | Endogenous Substances (up to listed concentrations, no significant interference): Bilirubin C (40 mg/dL), Bilirubin F (40 mg/dL), Cholesterol (300 mg/dL), Hemoglobin (1,000 mg/dL), Intralipid (500 mg/dL), Rheumatoid Factor (1,000 IU/mL), Triglycerides (1,000 mg/dL).
  Exogenous Substances (up to listed concentrations, no significant interference): Acetaminophen (1.5 mM), Amoxicillin (400 µmol/L), Aspirin (3.6 mM), Cephalexin (360 µmol/L), Fluconazole (480 µmol/L), Ibuprofen (2.5 mg/dL), Methotrexate (1,400 µmol/L), Prednisolone (2 µmol/L), Vitamin C (500 mg/L). |
  | Method Comparison: Strong correlation and minimal bias against the predicate device. | Regression Equation: y = 1.005x - 0.002, r = 0.999 (n = 175 clinical native serum samples), where y = K-ASSAY® CRP (Ver.2), x = predicate device. |
  | Linearity: Demonstrates linearity across the claimed assay range. | Regression Equation: y = 0.9709x - 1.095, r = 0.999 (tested range: 4.6 - 441.2 mg/L). |
  | Limit of Quantitation (LoQ): Clinically acceptable LoQ (within-laboratory precision ≤ 20% CV). | Reported LoQ: 1.0 mg/L (highest observed across 3 reagent lots). Claimed LoQ: 5.0 mg/L. |
  | Matrix Comparison: No significant difference in results across different sample matrices (serum vs. plasma). | K2-EDTA Plasma vs Serum: y = 1.007x - 0.141, r = 0.999
  Li-Heparin Plasma vs Serum: y = 0.972x + 0.074, r = 0.999 |
  | Expected Values (Verification): Distribution in normal population consistent with clinical literature. | 168 normal U.S. serum samples tested; 4 out of 168 samples (>5.0 mg/L, 2.4%) consistent with literature (≤ 5 mg/L indicates apparently healthy). |

2. Sample Sizes Used for the Test Set and Data Provenance

• Method Comparison: n = 175 clinical native serum samples.
• Linearity: The number of samples/dilutions used is not explicitly stated, but the tested range was 4.6 - 441.2 mg/L.
• Limit of Quantitation (LoQ): Not specified in terms of sample size for the LoQ determination itself (typically involves low-concentration samples measured multiple times).
• Matrix Comparison: 42 donor samples (each collected into 3 different tubes: serum, K2-EDTA plasma, Li-Heparin plasma).
• Precision (Single-site): For each of the 7 samples/controls, N=240 individual measurements (2 runs/day x 2 replicates/run x 20 days x 3 lots).
• Precision (Multisite): For each of the 7 samples/controls, N=75 individual measurements (1 run/day x 5 replicates/run x 5 days x 3 analyzers).
• Interference: The number of unique samples tested for interference is not explicitly stated. Typically, a few samples (e.g., low, medium, high concentration) are spiked with interferents and compared to unspiked controls.
• Expected Values: 168 normal serum samples.
• Data Provenance: The document states for "Expected Values" that 168 normal serum samples were "taken from healthy individuals in the U.S." This indicates a U.S. origin for at least this specific study. For other studies (Method Comparison, Precision, Linearity, Interference, Matrix Comparison), the specific country of origin is not mentioned. All studies are retrospectively analyzed in the sense that they were completed performance validation studies submitted to FDA.

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

For an in-vitro diagnostic device like this CRP assay, the "ground truth" is established through highly accurate and precise reference methods or established predicate devices, adhering to rigorous analytical chemistry best practices and guidelines (e.g., CLSI standards). There isn't a panel of human "experts" like radiologists interpreting images. The "ground truth" is quantitative and objective, derived from reference measurements.

In this case:

• Method Comparison: The predicate device (K-ASSAY® CRP (3), K023828) serves as the comparator for method comparison, which represents the established "ground truth" for clinical samples.
• Linearity, LoQ, Precision, Interference, Matrix Comparison: The "ground truth" for these analytical performance studies is established by rigorous laboratory protocols, highly calibrated equipment, reference materials, and adherence to CLSI guidelines. The performance is assessed against predefined statistical criteria rather than expert consensus on individual cases.
• Expected Values: The ground truth comes from established clinical literature and verified normal ranges based on studies of healthy populations.

4. Adjudication Method for the Test Set

Not applicable for an IVD device. Adjudication methods (e.g., 2+1, 3+1) are used in studies where subjective human interpretation (e.g., image reading) requires consensus building for ground truth establishment. For quantitative IVD assays, the results are numerical and objectively measured; therefore, there's no need for adjudication.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No. As explained above, this is an in-vitro diagnostic device, not an imaging AI/ML device involving human readers.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, in essence, all the analytical performance studies (Method Comparison, Linearity, LoQ, Precision, Interference, Matrix Comparison) are "standalone" in nature for an IVD. The device's performance is evaluated based solely on its ability to accurately and precisely measure CRP concentrations in samples, without any human interpretation of the measurement itself or the involvement of an "algorithm" in the AI/ML sense. The device directly processes the sample and outputs a quantitative result.

7. The Type of Ground Truth Used

The ground truth for this IVD device's performance studies is primarily based on:

• Reference Method/Predicate Device Comparison: For the method comparison study, the predicate device serves as the reference against which the new device's measurements are compared.
• Reference Materials and Calibrators: For linearity, LoQ, and precision studies, the ground truth for concentration values is established using certified reference materials and meticulously prepared calibrators with known concentrations.
• Spiked Samples: For interference studies, known amounts of interfering substances are added to samples, and the true CRP concentration (before interference) serves as the baseline ground truth.
• Clinical Literature/Established Norms: For "Expected Values," the ground truth is derived from widely accepted clinical ranges and population studies cited in the literature.

8. The Sample Size for the Training Set

This document describes a 510(k) submission for a traditional IVD device, not an AI/ML-based device. Therefore, there is no "training set" in the context of machine learning. The device's performance is based on its chemical and physical principles (latex-enhanced immunoturbidimetric assay) and validated through the analytical studies detailed.

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

Not applicable, as there is no "training set" for this type of IVD device.

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