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The Factor VIII Antibody Screen is a qualitative solid phase enzyme linked immunosorbent assay (ELISA) designed to detect IgG antibodies reactive with recombinant human factor VIII (FVII) in human serum and plasma.

The Factor VIII Antibody Screen is designed as a solid phase enzyme-linked immunosorbent assay (ELISA) with a colorimetric endpoint. This product is intended to be used as an in vitro diagnostic kit by hemostasis and other laboratories to screen patient samples for the presence of IgG antibodies reactive with human Factor VIII.

The Factor VIII Antibody Screen is an Enzyme Linked Immunosorbent Assay with a colorimetric endpoint. The Factor VIII Antibody Screen is designed to detect IgG antibodies reactive with recombinant human Factor VIII in human serum and plasma. The Factor VIII Antibody Screen kit contains all of the reagents necessary to perform the assay.

The Factor VIII Antibody Screen solid phase ELISA microwells provide immobilized recombinant human FVIII as target molecules for the detection of anti-Factor VIII IgG antibodies.

Diluted patient serum or plasma is added to microwells coated with recombinant FVIII molecules allowing antibody, if present, to bind. Unbound material is then washed away. An alkaline phosphatase labeled anti-human immunoglobulin reagent (Anti-IgG) is added to the wells and incubated. The unbound Anti-IgG is washed away and the substrate PNPP (p-nitrophenyl phosphate) is added. After a 30 minute incubation period, the reaction is stopped by a sodium hydroxide solution. The optical density of the color that develops is measured in a spectrophotometer at 405 nm with no reference filter.

Here's an analysis of the provided text to extract the acceptance criteria and study details:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly define a list of "acceptance criteria" with specific thresholds in a standardized table format. Instead, it discusses the performance against a predicate device and a "gold standard" (Bethesda assay), and establishes internal precision and reproducibility standards. Based on the "Conclusions" sections of the performance studies, here's a reconstructed table:

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

• Accuracy Study (Method Comparison):
  • Sample Size: "more than 200 samples"
  • Data Provenance: Combined internal study at GTI and an external study at the Special Coagulation Lab, Mayo Clinic, Rochester, MN, USA.
  • Sample Types: Serum, serum converted from plasma (3.2% or 3.8% sodium citrate), and plasma collected in ACD, from hemophiliac donors (with and without FVIII antibodies).
• Precision Study:
  • Sample Size: 8 samples
  • Data Provenance: Not explicitly stated, likely internal.
• Sample Type Qualification Study:
  • Sample Size:
    • 59 normal healthy, non-hemophiliacs (for serum vs. 3.2% sodium citrate plasma comparison).
    • 14 healthy, non-hemophilia donors (for serum vs. 3.2% sodium citrate vs. ACD plasma comparison).
    • Spiked samples: "12 plasma and serum pairs" and "24 plasma pairs" (for antibody positive plasma spiked into different matrices).
  • Data Provenance: Normal plasma samples were purchased as whole blood or collected from GTI employees. Antibody-positive samples were, by inference, either existing positive samples or spiked for the experiment.
• Interfering Substances Study:
  • Sample Size: 3 samples (1 negative, 1 with medium reactivity, 1 with high reactivity)
  • Data Provenance: Internal study at GTI.
• Lot-to-Lot Reproducibility Study:
  • Sample Size: 12 samples (7 known negative, 5 known positive)
  • Data Provenance: Not explicitly stated, likely internal.
• Shelf-life Study:
  • Sample Size:
    • Accelerated microwell stability: "no time points constituted a failed assay" (implies multiple tests).
    • Real-time kit stability: 3 kit lots tested with "known negative sample" and "known positive samples" (number of samples not specified, but at least two: one negative, one positive).
  • Data Provenance: Internal testing at GTI.

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

The document does not specify the number of experts or their qualifications for establishing ground truth.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method for the test set. Ground truth was established by comparison to existing assays (Factor VIII Inhibitor Assay and Bethesda assay).

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No multi-reader multi-case (MRMC) comparative effectiveness study was mentioned. The device is an in vitro diagnostic (IVD) ELISA test, not an imaging or interpretation device that would typically involve human readers.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

Yes, the studies described are for the standalone performance of the Factor VIII Antibody Screen kit as an in vitro diagnostic device. There is no human-in-the-loop component mentioned for the interpretation of the optical density (OD) values, which are converted to positive/negative based on a predefined cutoff relative to a kit control.

7. Type of Ground Truth Used

• Comparator Assays:
  • For Accuracy studies: The primary ground truth was established by comparison to the GTI Factor VIII Inhibitor Assay (predicate device) and the Bethesda assay. The Bethesda assay is explicitly stated as the "gold standard for detection and quantitation of inhibitory antibodies to Factor VIII."
  • For the method comparison, samples were categorized as "hemophiliac donors without Factor VIII antibodies (negative Bethesda titers or a negative Bethesda Screen)" and "hemophiliac donors with Factor VIII antibodies (positive Bethesda titers)."
• Internal Standards:
  • For Precision, Sample Type Qualification, Interfering Substances, and Lot-to-Lot Reproducibility studies, ground truth relied on "known negative samples" and "known positive samples" or spiked samples, implying prior characterization or experimental manipulation.
  • The kit control itself is based on a "diluted serum known to contain antibodies to Factor VII."

8. Sample Size for the Training Set

The document does not explicitly describe a "training set" in the context of an algorithm or machine learning model. However, the Factor VIII Antibody Screen Assay Cutoff study involved determining the appropriate value for the kit control. This process can be seen as analogous to establishing a threshold or "training" the cutoff for optimal discrimination.

• Cutoff Determination Study (analogous to training set):
  • Sample Size: 78 different serum samples from normal, healthy, non-hemophilic donors and 3 known positive samples with low reactivity.

9. How Ground Truth for the Training Set Was Established

For the Cutoff Determination Study:

• Normal Samples: "normal, healthy, non-hemophiliacs." The average OD value for these 78 normal samples was calculated.
• Positive Samples: "3 known positive samples with low reactivity."
• Method: A target cutoff value for the kit control was chosen to be three times (3x) the average OD value of the normal samples. A specific dilution of a FVIII antibody positive serum was then selected to match this target OD, with the additional constraint that the 3 known positive samples with low reactivity must be positive and >98% of the normal samples must be negative. This iterative process established the "ground truth" for setting the kit's operational cutoff.

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