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CRYOcheck Chromogenic Factor VIII is for clinical laboratory use in the quantitative determination of factor VIII activity in 3.2 % citrated human plasma. It is intended to be used in identifying factor VIII deficiency and as an aid in the management of hemophilia A in individuals aged 2 years and older. For in vitro diagnostic use.

CRYOcheck Chromogenic Factor VIII is used for determination of FVIII activity and contains the following four components, packaged in glass vials and provided frozen to preserve the integrity of the components:

• Reagent 1: Bovine FX and a fibrin polymerization inhibitor, with activators and stabilizer.
• Reagent 2: Human FIIa, bovine FIXa, calcium chloride and phospholipids.
• Reagent 3: FXa substrate containing EDTA and a thrombin inhibitor.
• Diluent Buffer: Tris buffer solution containing 1% BSA and a heparin antagonist.

In the first stage of the chromogenic assay, test plasma (containing an unknown amount of functional FVIII) is added to a reaction mixture comprised of calcium, phospholipids, human purified thrombin and FIXa, and bovine FX (Reagent 1 and Reagent 2). This mixture swiftly activates FVIII to FVIIIa, which works in concert with FIXa to activate FX. When the reaction is stopped, FXa production is assumed to be proportional to the amount of functional FVIII present in the sample. The second stage of the assay is to measure FXa through cleavage of a FXa-specific peptide nitroanilide substrate (FXa Substrate). P-nitroaniline is produced, giving a color that can be measured spectrophotometrically by absorbance at 405 nm.

Based on the provided FDA 510(k) Clearance Letter, the device in question is the CRYOcheck Chromogenic Factor VIII. This document details the clearance of a modified version of an existing device, emphasizing the differences from the previous version regarding interference claims and recovery of Factor VIII replacement therapies.

Here's an analysis of the acceptance criteria and study proving the device meets them, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state "acceptance criteria" for each performance claim in a quantified manner (e.g., "Interference must be less than X%"). Instead, it reports the limits of non-interference found in their studies, implying these served as the de facto acceptance criteria. For the Factor VIII replacement therapy recovery, the acceptance criterion appears to be "accurate evaluation" across a range of concentrations, with specific over/under recovery noted.

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

• Interference Studies: Plasma samples were "spiked with possible interferents," and "10 replicates were tested alongside 10 replicates of the corresponding blank matrix control." The total number of individual patient samples from which this plasma was derived is not specified, nor is the country of origin. The study design implies a prospective spiking experiment in a laboratory setting.
• Recovery of Factor VIII Replacement Therapy: "Congenital FVIII deficient plasma was spiked with 14 FVIII replacement therapies at seven concentrations." The number of individual patient plasma units or lots of deficient plasma used is not specified. The study design implies a prospective spiking experiment in a laboratory setting.

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

N/A. This is an in vitro diagnostic device for quantitative determination of factor VIII activity, not an AI/imaging device requiring expert human readers for ground truth generation. The ground truth for these studies is established by the known concentrations of spiked interferents or FVIII replacement therapies, and the intrinsic properties of the FVIII deficient plasma.

4. Adjudication Method for the Test Set

N/A. As this is a quantitative in vitro diagnostic device, an adjudication method in the context of human expert review of imaging or clinical data is not applicable. The results are measured spectrophotometrically.

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

No, an MRMC study was not done. This type of study is relevant for AI imaging devices where human readers interpret medical images with and without AI assistance. This document describes an in vitro diagnostic device.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) was Done

Yes, this entire submission describes the standalone performance of the CRYOcheck Chromogenic Factor VIII assay. The device itself performs the quantitative determination of FVIII activity, entirely without a "human-in-the-loop" once the sample is loaded and the assay run according to protocol.

7. The Type of Ground Truth Used

• Interference Studies: The ground truth was the known concentration of the spiked interferent (e.g., Hemoglobin, Intralipid, Bilirubin, etc.) added to plasma samples, and the corresponding blank matrix control.
• Recovery of Factor VIII Replacement Therapy: The ground truth was the known concentration of the spiked FVIII replacement therapy added to congenital FVIII deficient plasma at various concentrations.

8. The Sample Size for the Training Set

N/A. This document describes an in vitro diagnostic assay based on chromogenic principles, not an AI/ML algorithm that requires a "training set" in the computational sense. The device's components (reagents, diluent buffer) and their interaction define the assay, which is then validated through performance studies.

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

N/A. See point 8. The "ground truth" for developing and optimizing such a chromogenic assay would stem from extensive biochemical research, characterization of reagents, and titrations against known standards, which is inherent in the development of any diagnostic assay, but not referred to as a "training set" or "ground truth establishment" in the AI/ML context.

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CRYOcheck Chromogenic Factor VIII is for clinical laboratory use in the quantitative determination of factor VIII activity in 3.2% citrated human plasma. It is intended to be used in identifying factor VIII deficiency and as an aid in the management of hemophilia A in individuals aged 2 years and older. For in vitro diagnostic use.

CRYOcheck Chromogenic Factor VIII is used for determination of FVIII activity and contains the following four components, packaged in glass vials and provided frozen to preserve the integrity of the components:
Reagent 1: Bovine FX and a fibrin polymerization inhibitor, with activators and stabilizers.
Reagent 2: Human FIIa, human FIXa, calcium chloride and phospholipids.
Reagent 3: FXa substrate containing EDTA and a thrombin inhibitor.
Diluent Buffer: Tris buffer solution containing 1% BSA and a heparin antagonist.

The CRYOcheck Chromogenic Factor VIII device is intended for the quantitative determination of Factor VIII (FVIII) activity in human plasma to identify FVIII deficiency and aid in Hemophilia A management.

Here's an analysis based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are generally implied by the successful outcomes of various studies, aligning with CLSI guidelines and demonstrating performance comparable to the predicate device. Specific numerical acceptance criteria were not explicitly stated as pass/fail thresholds in the document, but the reported performance values are presented as the fulfillment of these criteria.

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

• Precision Study: One normal and two abnormal reference controls, and five patient plasma samples (representing very low, mid, normal, and high FVIII activity). Each sample was measured in duplicate, twice a day for 20 days (total 80 replicates per sample per lot) with 3 lots of the device. Data provenance is internal (as it's an internal study).
• Reproducibility Study: One normal and two abnormal reference controls, and three patient plasma samples (representing very low, normal, and high FVIII activity). Each sample was measured in triplicate, twice a day for 5 days at each of 3 sites with 3 lots of the device. Data provenance includes one internal and two external sites, but specific countries are not mentioned beyond "Canada" for the submitter. This appears to be prospective data collection for the study.
• Linearity/Assay Reportable Range Study: Fifteen sample dilutions created by combining high FVIII plasma (260%) with congenital FVIII deficient plasma (0%). Each level was tested in quadruplicate. Data provenance is internal (as it implies an internal study).
• Reference Interval Study: One hundred and twenty ostensibly healthy individuals $\geq$ 18 years. Data provenance is not specified beyond "citrated plasma samples collected from". This appears to be prospective data collection.
• Shelf-Life Stability Study: Six plasma samples representing low to normal FVIII activity levels. Three lots of the device were tested at various time points up to 37 months (13 months completed). Data provenance is internal.
• In-Use Stability Study: Six plasma samples representing low to normal FVIII activity levels. Three lots of the device were tested at various time points. Data provenance is internal.
• Detection Limit (LoB/LoD/LoQ) Studies:
  • LoB: Four blank plasma samples from individuals with severe congenital hemophilia A.
  • LoD: Four plasma samples with low FVIII activity from congenital hemophilia A donors.
  • LoQ: Aliquots of four plasma samples with low FVIII activity from congenital hemophilia A donors.
    All samples for LoB/LoD were measured in triplicate over five days using three lots of the device. For LoQ, samples were tested in triplicate on five different days at an external laboratory. Data provenance for LoB/LoD/LoQ samples is from individuals with hemophilia A.
• Interference Studies: Plasma samples spiked with possible interferents. Ten replicates of each spiked sample and 10 replicates of corresponding blank matrix control were tested. Data provenance is internal.
• Method Comparison Studies: Three hundred and eighteen human plasma samples from normal individuals, patients with congenital or acquired hemophilia A, and various types of von Willebrand disease. Samples were distributed across three sites. Data provenance spans "normal ostensibly healthy individuals and from patients". This appears to be prospective data collection.
• Sample Integrity Study: Forty-six plasma samples. Data provenance is not further specified. This appears to be prospective data collection at two external sites.

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

For this in vitro diagnostic device, "ground truth" is typically established by reference methods or accepted clinical classifications rather than expert consensus on individual images or cases.

• For studies like Precision, Reproducibility, Linearity, Stability, and Detection Limits, the "ground truth" for the FVIII activity levels in controls and calibrators would be established by the manufacturer's internal characterization methods, traceable to international standards if applicable (though not explicitly stated as such for FVIII activity). The expertise would lie in clinical chemistry, hematology, and laboratory medicine for the development and validation of these reference materials and methods. No specific number or qualification of experts is mentioned for these.
• For the Reference Interval Study, the ground truth is derived from the statistical distribution of FVIII activity in a population of ostensibly healthy individuals. This doesn't involve individual expert ground-truthing but rather statistical analysis.
• For the Method Comparison Study, the ground truth for FVIII activity was established by a comparator device, Coatest SP FVIII (K042576), used at a central reference laboratory. The "experts" in this context are the trained laboratory personnel performing the reference method.
• For sample selection in studies involving "congenital hemophilia A donors" or "patients with congenital or acquired hemophilia A and various types of von Willebrand disease," the diagnosis (which forms part of the "ground truth" for classifying these samples) would have been made by medical professionals (e.g., hematologists) based on standard clinical and laboratory diagnostic criteria. No specific number or qualifications are given.

4. Adjudication Method for the Test Set

Adjudication methods like "2+1" or "3+1" are typically used for subjective diagnostic tasks, often involving image interpretation or clinical reviews. Since the CRYOcheck Chromogenic Factor VIII is a quantitative assay for FVIII activity, the "adjudication method" is the quantitative measurement itself, often with replicates and statistical analysis, as detailed in the study designs (e.g., "in duplicate," "in triplicate"). No expert adjudication in the traditional sense is described or expected for this type of device.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and the Effect Size

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. MRMC studies are primarily for evaluating the impact of a new diagnostic tool on the diagnostic performance of human readers, typically with subjective assessments. This device is a quantitative in vitro diagnostic, not a tool for human reading in the conventional sense.

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

Yes, the device operates as a standalone algorithm (assay) measuring FVIII activity. The performance studies described (Precision, Reproducibility, Linearity, Reference Interval, Stability, Detection Limits, Interferences, Method Comparison, Sample Integrity) all represent the performance of the device itself, without human-in-the-loop diagnostic interpretation as part of its core function, other than trained laboratory personnel operating the instrument and interpreting numerical output.

7. The Type of Ground Truth Used

The ground truth used for these studies varies by the specific test:

• Reference materials and controls: For precision, linearity, and detection limit studies, the ground truth for FVIII activity levels is based on established values of these materials, likely traceable to international standards or well-characterized internal standards.
• Healthy population data: For the reference interval, the ground truth for "normal" FVIII activity is derived from a statistically representative healthy population.
• Comparator device: For the method comparison study, the ground truth was established by the predicate device, Coatest SP FVIII (K042576).
• Clinical diagnosis: For studies involving patient samples (e.g., hemophilia A, von Willebrand disease), the ground truth for their disease status would be based on clinical diagnosis by medical professionals.

8. The Sample Size for the Training Set

The document describes performance studies (validation tests) for the device. It does not provide information on a "training set" in the context of machine learning. This is because the device is a chemical assay, not an AI/ML-based diagnostic system that would require a training set to develop its model.

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

As no training set is mentioned or applicable for this type of chemical assay device, this question is not relevant based on the provided information.

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