(108 days)
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.
| Performance Characteristic | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|
| Interference: | ||
| Hemoglobin | Must show no interference up to the concentration indicated. | No interference observed up to ≤1000 mg/dL (increased from ≤500 mg/dL) |
| Intralipid | Must show no interference up to the concentration indicated. | No interference observed up to ≤830 mg/dL (increased from ≤500 mg/dL) |
| Bilirubin (unconjugated) | Must show no interference up to the concentration indicated. | No interference observed up to ≤40 mg/dL (increased from ≤29 mg/dL) |
| Bilirubin (conjugated) | Must show no interference up to the concentration indicated. | No interference observed up to ≤11 mg/dL (increased from ≤2 mg/dL) |
| von Willebrand factor | Must show no interference up to the concentration indicated. | No interference observed up to ≤20 µg/mL (same) |
| Unfractionated heparin | Must show no interference up to the concentration indicated. | No interference observed up to ≤3.3 IU/mL (increased from ≤2 IU/mL) |
| Low molecular weight heparin | Must show no interference up to the concentration indicated. | No interference observed up to ≤5 IU/mL (increased from ≤2 IU/mL) |
| Fondaparinux | Must show no interference up to the concentration indicated. | No interference observed up to ≤0.2 mg/L (decreased from ≤1.25 mg/L) |
| Lupus Anticoagulant | Must show no interference up to the concentration indicated. | No interference observed up to ≤1.8 dRVVT ratio (same) |
| Emicizumab | Must show no interference up to the concentration indicated. | No interference observed up to ≤150 µg/mL (new claim) |
| Mim8 | Must show no interference up to the concentration indicated. | No interference observed up to ≤8 µg/mL (new claim) |
| Warfarin | Must show no interference up to the concentration indicated. | No interference observed up to INR ≤7 (new claim) |
| Rivaroxaban | Must not interfere. | Interfered with quantification of FVIII activity. |
| Dabigatran | Must not interfere. | Interfered with quantification of FVIII activity. |
| Recovery of FVIII Replacement Therapy: | Must accurately evaluate potency. | Accurately evaluated potency for ADVATE, ADYNOVATE, AFSTYLA, ALTUVIIO, ESPEROCT, HUMATE-P, JIVI, KOVALTRY, Novoeight, Nuwiq, and wilate at 0.05-1.0 IU/mL; ELOCTATE, and XYNTHA at 0.05-0.6 IU/mL (with over recovery at 0.8 & 1.0 IU/mL); Underestimation for OBIZUR. |
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.
§ 864.7290 Factor deficiency test.
(a)
Identification. A factor deficiency test is a device used to diagnose specific coagulation defects, to monitor certain types of therapy, to detect coagulation inhibitors, and to detect a carrier state (a person carrying both a recessive gene for a coagulation factor deficiency such as hemophilia and the corresponding normal gene).(b)
Classification. Class II (performance standards).