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Diazyme Cystatin C Point-of Care (POC) test reagents are intended for use with the SMART analyzer for the quantitative determination of Cystatin C in venous whole blood by latex enhanced immunoturbidimetric method. The measurement of Cystatin C is used as an aid in the diagnosis and treatment of renal disease. For in vitro Diagnostic Use Only.

The Diazyme Cystatin C POC Test Control Kit is intended for use as quality controls for the Cystatin C POC Test. For in vitro Diagnostic Use Only.

Diazyme Cystatin C POC Test Kit contains reagents intended for use with the SMART analyzer for the quantitative determination of Cystatin C (Cys C) in human venous whole blood samples. Measurement of Cystatin C can assist in the assessment of renal transplantation status, monitoring GFR in nephrotoxic drug therapy, and monitoring GFR in acute and chronic kidney diseases including diabetic nephropathy. Cystatin C POC Test reagents are similar to the predicate Diazyme Cystatin C assay reagents (K093680). The similarities and differences in composition and format are noted in Table 1 below. The Cystatin C POC Test is based on a latex enhanced immunoturbidimetric assay. Cystatin C in the venous whole blood sample binds to the specific anti-Cystatin C antibody, which is coated on latex particles, and causes agglutination. The degree of the turbidity caused by agglutination can be measured optically and is proportional to the amount of Cystatin C in the venous whole blood sample. The Cystatin C concentration is expressed as mg/L Cystatin C by use of a lot specific calibration curve that is stored in an RFID card provided with each SMART test kit.

Diazyme Cystatin C POC Test Control Kit is intended for use as quality controls for the Diazyme Cystatin C POC Test and is packaged separately. The controls are made from human venous whole blood and are in a lyophilized (freeze-dried) state. The quality controls assist laboratory users in verification steps ensuring that the assay reagents are functioning correctly. QC materials are run exactly as samples. Users are instructed to verify the calibration curve with the controls and run controls each time a new lot of reagents are received. If OC materials fall outside laboratory acceptable range, users are instructed to re-test and call manufacturer customer service if problem persists.

SMART Analyzer (K092911) is a compact cuvette based spectrophotometer (10 inches x 5.5 inches x 5.5 inches) machine for point-of-care testing designed to analyze readings from single use reagent cuyette. The instrument only uses the Diazyme Reagent System (DRS) cuvette and caps and performs assay with a preprogrammed Radio Frequency ID (RFID) card. The DRS cuvette is supplied prefilled with Reagent 1 (R1) and the DRS cap is supplied prefilled with Reagent 2 (R2). The DRS cuvette and caps are kept separate until use. Users are instructed (see proposed labeling) to add 20ul of sample to the DRS cuvette prefilled with R1 containing proper amount of detergent for venous whole blood lysis. Users are then instructed to snap in place DRS cap and insert into analyzer. The instrument warms the cuvette to 37°C and after a predefined period adds the reagent R2 found in the DRS cap. The reagents and samples are mixed magnetically and absorbance readings are taken at 700nm. The lot specific RFID card contains reagent addition time, mixing time, reading time and calibration curve.

The Diazyme Cystatin C POC Test is a device intended for the quantitative determination of Cystatin C in venous whole blood using a latex-enhanced immunoturbidimetric method with the SMART analyzer. The measurement of Cystatin C aids in the diagnosis and treatment of renal disease.

1. Table of Acceptance Criteria and Reported Device Performance

The provided document does not explicitly state "acceptance criteria" but presents performance characteristics that were evaluated for substantial equivalence to a predicate device. The performance of the Diazyme Cystatin C POC Test is compared against a predicate device (Diazyme Cystatin C Assay, K093680). The table below summarizes the reported performance for the candidate device, which implicitly serves as the performance values that met the substantial equivalence requirements.

• Samples 0.70 mg/L & 0.99 mg/L: 5.6% to 6.9% | The reported CVs for the candidate device are generally within or close to the 1.0 mg/L: 2.2% to 4.9%
• Samples 0.70 mg/L & 0.99 mg/L: 5.6% to 6.9%
  3 POL Sites:
• Samples > 1.0 mg/L: 2.6% to 8.0%
• Samples 0.55 mg/L & 0.93 mg/L: 5.3% to 9.1% |
  | Accuracy (Correlation Coefficient R²) | 0.99 | Diazyme Lab: R² = 0.9867
  3 POL Sites: R² = 0.9872 | Similar |
  | Accuracy (Slope) | 0.99 | Diazyme Lab: 0.9535
  3 POL Sites: 0.955 | Similar |
  | Accuracy (Intercept) | 0.0877 | Diazyme Lab: 0.0985
  3 POL Sites: 0.0732 | Similar |
  | Linearity/Reportable Range (R²) | Not specified | R² = 0.9977 (up to 7.65 mg/L) | Demonstrated strong linearity. |
  | LoB | Not specified | 0.045 mg/L | Established. |
  | LoD | Not specified | 0.11 mg/L | Established. |
  | LoQ | Not specified | 0.30 mg/L | Established, defining the lower end of the AMR. |
  | Interference | Not specified | No significant interference from common substances up to specified concentrations. | Demonstrated analytical specificity. |
  | Expected/Reference Range | Not specified | 0.46 to 1.06 mg/L (in 95% of healthy adults) | Confirmed transferability of reference interval. |

2. Sample 사이즈 used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)

• Precision Study:
  • Sample Size: 6 whole blood specimens were tested. Each specimen was run in duplicates, twice a day, over 10 working days on three different SMART Analyzers. This totals (2 runs/day * 2 duplicates/run * 10 days * 3 analyzers) = 120 data points per specimen, but the table reports "Total data points: 40" per specimen for within-run and total precision, implying 40 measurements per specimen over the study period (perhaps per analyzer or across all analyzers).
  • Data Provenance: The study was conducted internally at Diazyme Laboratories, implying internal prospective testing of samples. No specific country of origin is mentioned beyond Diazyme's location in Poway, CA, USA.
• Linearity Study:
  • Sample Size: Eleven levels of Cystatin C concentrations were prepared from a whole blood sample and run in triplicates.
  • Data Provenance: Internal to Diazyme Laboratories.
• LoB, LoD, LoQ:
  • Sample Size: Not explicitly stated but usually involves multiple replicates of blank and low-concentration samples.
  • Data Provenance: Internal to Diazyme Laboratories.
• Interference Study:
  • Sample Size: Two whole blood samples ("low" and "high" Cystatin C) spiked with various concentrations of interfering substances.
  • Data Provenance: Internal to Diazyme Laboratories.
• Method Comparison with Predicate Device (Accuracy Study):
  • Internal Method Comparison:
    • Sample Size: Fifty-five (55) paired human whole blood-serum samples (venous whole blood and plasma from the same individual).
    • Data Provenance: Conducted internally at Diazyme Laboratories, likely prospective.
  • External Method Comparison:
    • Sample Size: One hundred and twenty (120) whole blood samples (40 samples per site) tested at three Point-of-Care (POL) sites. Corresponding plasma specimens (120) were tested with the predicate device.
    • Data Provenance: Conducted externally at three POL sites by intended users, implying prospective testing in real-world settings.
• Expected Values/Reference Range Study:
  • Sample Size: 126 apparently healthy adults.
  • Data Provenance: Whole blood samples were tested using the Diazyme Cystatin C SMART assay, likely collected prospectively for this study, though the specific origin is not stated beyond Diazyme. Age range of participants was 19-63.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)

This device is an in vitro diagnostic (IVD) test for quantitative determination of a biomarker (Cystatin C). The "ground truth" for such devices is typically established through reference methods or established assays, rather than expert consensus on interpretive tasks like in imaging.

• For the accuracy/method comparison studies (test set): The predicate device, Diazyme Cystatin C Assay (K093680), run on a Hitachi 917 analyzer, served as the reference method or "ground truth" comparator for the comparison studies. The performance of the predicate device itself would have been established against a recognized gold standard during its own clearance process.
• Number/Qualifications of Experts: The document does not specify experts establishing ground truth in the traditional sense of clinical interpretation. The "experts" involved would be the clinical laboratory professionals operating the predicate device and the new device. Their qualifications are not detailed but are assumed to be standard for clinical laboratory practice.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set

Not applicable. For quantitative diagnostic tests measuring a biomarker, adjudication methods typically used for qualitative or interpretive tasks (like imaging analysis) are not relevant. The "ground truth" is determined by the result of the reference method (predicate device) and direct comparison of quantitative values. Statistical methods (e.g., regression analysis) are used to assess agreement.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

Not applicable. This is an in vitro diagnostic device, not an AI-assisted diagnostic imaging or interpretive aid. It directly measures a biomarker. The studies involved comparing the performance of the new device to a predicate device, not the improvement of human reader performance with or without AI.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

Yes, the studies present the standalone performance of the Diazyme Cystatin C POC Test System. The device provides a quantitative result for Cystatin C. The performance metrics reported (precision, linearity, accuracy, LoB, LoD, LoQ, interference) reflect the performance of the device system (reagents + SMART analyzer) itself, without direct human cognitive interpretation of the final result for diagnostic purposes. Humans operate the device and interpret the numerical output in the context of clinical guidelines, but the "performance" described is that of the automated measurement system.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)

• Method Comparison Studies: The "ground truth" was established by comparison to a legally marketed predicate device (Diazyme Cystatin C Assay, K093680) run on a Hitachi 917 analyzer. This is a common approach for demonstrating substantial equivalence for new IVD devices.
• Other Performance Studies (Precision, Linearity, LoB/LoD/LoQ, Interference): These studies assess the intrinsic analytical performance of the device against predefined analytical standards (e.g., CLSI guidelines), often using prepared control materials or spiked samples where the "true" concentration is known or assumed from the preparation.

8. The sample size for the training set

This document describes a pre-market notification (510(k)) for a traditional IVD device, not a machine learning or AI-driven algorithm. Therefore, the concept of a "training set" in the context of AI model development is not directly applicable here.

The device's calibration curve is established using a lot-specific RFID card provided with each kit. This implies a calibration process performed by the manufacturer, which might involve a set of calibrators, but it's not a "training set" for an AI algorithm.

9. How the ground truth for the training set was established

Not applicable, as no AI/machine learning training set is described for this conventional IVD device. The calibration for the device is performed using a lot-specific calibration curve stored on an RFID card. The accuracy of this calibration would be verified during manufacturing and quality control processes.

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