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510(k) Data Aggregation
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N Latex Cystatin C: N Latex Cystatin C is an in vitro diagnostics kit containing reagents for the quantitative determination of cystatin C in human serum and lithium-heparinized plasma by means of particle-enhanced immunonephelometry using the BN Systems. Cystatin C measurements are used in the diagnosis and treatment of renal diseases. N Protein Standard UY: N Protein Standard UY is used for preparing reference curves for the immunonephelometric determination of a1microglobulin and Cystatin C using the BN Systems.
The N Latex Cystatin C is an in vitro diagnostics kit containing reagents for the quantitative determination of cystatin C in human serum and lithium heparinized plasma by means of particle-enhanced immunonephelometry using the BN II and BN ProSpec® Systems. Used in conjunction with other clinical and laboratory findings, N Latex Cystatin C measurements are used as an aid in the diagnosis and treatment of renal diseases. Used in conjunction with the assay reagents, N Protein Standard UY is for use in the establishment of reference curves for the determination of cystatin C on the BN II and BN ProSpec Systems. N Cystatin C Control 1 and 2 are included with N Latex Cystatin C kit and are for use as assayed accuracy controls and precision controls in the determination of cystatin C by immunonephelometry with the BN II and BN ProSpec Systems. The N Latex Cystatin C test system is based upon the principles of particle-enhanced immunonephelometry. Polystyrene particles coated with specific antibodies to human cystatin C are aggregated when mixed with samples containing human cystatin C. These aggregates scatter a beam of light passed through the sample. The intensity of the scattered light is proportional to the concentration of the respective protein in the sample. The result is evaluated by comparison with a standard of known concentration.
Acceptance Criteria and Device Performance for N Latex Cystatin C
This document summarizes the acceptance criteria and performance study results for the N Latex Cystatin C device, as described in the provided FDA 510(k) summary (K171072).
1. Table of Acceptance Criteria and Reported Device Performance
The provided document details performance studies but does not explicitly define a "table of acceptance criteria". Instead, it describes established methodologies and states that "Results met the pre-established acceptance criteria." for the method comparison study. Based on the reported data, the following can be inferred as performance metrics that met the sponsor's internal acceptance criteria for substantial equivalence:
| Performance Characteristic | Acceptance Criteria (Inferred from reported data) | Reported Device Performance (N Latex Cystatin C) |
|---|---|---|
| Precision | CVs within acceptable ranges for repeatability and within-device/lab precision, especially near the medical decision point. | BN ProSpec: - CysC Control 1: Repeatability CV 1.78%, Within-device/lab CV 1.78% - CysC Control 2: Repeatability CV 1.00%, Within-device/lab CV 1.01% - Serum Pool 1: Repeatability CV 3.85%, Within-device/lab CV 3.85% - Serum Pool 2: Repeatability CV 1.39%, Within-device/lab CV 1.41% - Serum Pool 3: Repeatability CV 1.62%, Within-device/lab CV 1.62% - Plasma Pool 1: Repeatability CV 2.38%, Within-device/lab CV 2.65% - Plasma Pool 2: Repeatability CV 2.09%, Within-device/lab CV 2.09% - Plasma Pool 3: Repeatability CV 1.07%, Within-device/lab CV 1.26% BN II: - CysC Control 1: Repeatability CV 1.93%, Within-device/lab CV 2.24% - CysC Control 2: Repeatability CV 1.42%, Within-device/lab CV 1.54% - Serum Pool 1: Repeatability CV 2.54%, Within-device/lab CV 2.62% - Serum Pool 2: Repeatability CV 1.34%, Within-device/lab CV 1.55% - Serum Pool 3: Repeatability CV 1.69%, Within-device/lab CV 1.80% - Plasma Pool 1: Repeatability CV 2.59%, Within-device/lab CV 2.59% - Plasma Pool 2: Repeatability CV 1.62%, Within-device/lab CV 1.75% - Plasma Pool 3: Repeatability CV 1.98%, Within-device/lab CV 2.42% |
| Measuring Range (Linearity) | Acceptable linearity over the specified range. | Demonstrated linearity over the range of 0.27 to 10.3 mg/L. |
| Limit of Quantitation (LoQ) | LoQ at a specified %CV (e.g., <8% CV). | LoQ demonstrated to be 0.08 mg/L at < 8% CV. |
| High Dose Hook Effect (Antigen Excess) | No high dose hook or prozone effects up to a specified concentration. | No high dose hook or prozone effects up to 42.91 mg/L. |
| Method Comparison (Correlation Coefficient) | High correlation (e.g., r close to 1). | BN ProSpec vs. Tina-quant: r = 0.988 BN II vs. Tina-quant: r = 0.998 |
| Method Comparison (Slope) | Slope close to 1 (indicating proportional agreement with predicate). | BN ProSpec vs. Tina-quant: Slope = 0.982 BN II vs. Tina-quant: Slope = 0.981 |
| Method Comparison (Intercept) | Intercept close to 0 (indicating lack of constant bias with predicate). | BN ProSpec vs. Tina-quant: Intercept = -0.078 mg/L BN II vs. Tina-quant: Intercept = -0.079 mg/L |
2. Sample Size Used for the Test Set and Data Provenance
- Precision: The precision studies used 80 replicates for each control and serum/plasma pool (e.g., CysC Control 1, Serum Pool 1, Plasma Pool 1, etc.) on both the BN ProSpec and BN II instruments. The data provenance is Siemens Healthcare Diagnostics Products, Marburg, Germany (internal study).
- Measuring Range (Linearity): Not explicitly stated, but "Each dilution was tested in replicates of five using an individual aliquot." The exact number of dilutions is not provided. Data provenance is Siemens Healthcare Diagnostics Products, Marburg, Germany (internal study).
- Limit of Quantitation (LoQ): Not explicitly stated, but implies multiple measurements according to CLSI EP17-A2. Data provenance is Siemens Healthcare Diagnostics Products, Marburg, Germany (internal study).
- High Dose Hook Effect: "Each dilution was run five times." The exact number of dilutions is not specified. Data provenance is Siemens Healthcare Diagnostics Products, Marburg, Germany (internal study).
- Reference Interval Study: 203 serum samples from a US population. This data is prospective (samples measured specifically for this study).
- Method Comparison: 186 serum samples. The study was conducted at one external site in the United States. This data is implicitly prospective (samples measured for the comparison).
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not describe the use of "experts" to establish ground truth in the traditional sense for diagnostic device performance (e.g., for image interpretation). Instead, the performance studies, particularly method comparison, relied on comparison to a legally marketed predicate device (Tina-quant Cystatin C Gen.2) and established reference methods (traceability to ERM-DA471/IFCC).
4. Adjudication Method for the Test Set
Adjudication methods (e.g., 2+1, 3+1) are typically used for subjective assessments or when there's ambiguity in ground truth determination, often in scenarios involving human interpretative tasks. This is not applicable to the quantitative analytical performance studies described for the N Latex Cystatin C, where measurements are objective.
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done
No. The provided document describes the performance of a diagnostic assay (N Latex Cystatin C) used for quantitative determination of cystatin C. MRMC studies are typically for evaluating diagnostic imaging devices or other tools where human interpretation plays a significant role, and there's interaction between human readers and the AI/device output. This is not relevant for this type of in vitro diagnostic device.
6. If a Standalone (i.e. Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, the performance studies detailed (e.g., precision, linearity, LoQ, high dose hook effect, method comparison) represent the standalone performance of the N Latex Cystatin C assay on the BN II and BN ProSpec systems. These are automated systems that produce quantitative results based on the assay's chemical reactions, without direct human intervention in the result determination beyond instrument operation and sample loading.
7. The Type of Ground Truth Used
- Precision, Linearity, LoQ, High Dose Hook Effect: The ground truth for these analytical performance studies is based on consensus reference values (e.g., value of controls, spiked samples) and the inherent performance characteristics of the instrument and assay method itself. The method relies on the principle of particle-enhanced immunonephelometry, where the intensity of scattered light is proportional to the concentration of cystatin C, which is the "ground truth" being measured by the method.
- Reference Interval Study: The ground truth for establishing the reference interval was the measured Cystatin C concentrations in serum samples from a "US population of apparently healthy adults or patients with diseases not linked to renal disease or failure."
- Method Comparison: The ground truth for the method comparison study was the results obtained from the legally marketed predicate device, Tina-quant Cystatin C Gen.2 assay, on Roche cobas systems. The new device's performance was evaluated against this established method.
- Traceability: The ultimate ground truth/standardization for Cystatin C measurement for the device is the IFCC European Reference Material ERM-DA471/IFCC.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of machine learning or AI models. This device is an in vitro diagnostic assay, not a software algorithm that learns from data in that manner. The development and optimization of the assay would have involved various internal studies and analytical evaluations, which could be considered analogous to "training" in a broader sense of product development, but not in the specific context of AI model training.
9. How the Ground Truth for the Training Set Was Established
As noted above, there is no "training set" in the common AI/machine learning sense described in this 510(k) summary. The "ground truth" for the development of the N Latex Cystatin C assay reagents and calibrators involves established chemical and immunological principles, and calibration traceable to a recognized international reference material (ERM-DA471/IFCC). The "ground truth" in this context refers to the accurate and precise measurement of cystatin C concentrations based on validated methodologies and standards.
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