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PF4 IgG assay is a qualitative screening assay for the detection of heparin associated IgG antibodies in human serum or plasma. The presence of heparin-associated antibodies are commonly found in patients with Heparin Induced Thrombocytopenia (HIT).

PF4 IgG assay is an enzyme linked immunosorbent assay (ELISA). The PF4 IgG ELISA is intended to detect IgG antibodies in human serum or plasma that react with Platelet Factor 4 (PF4) when it is complexed to heparin or other polyanionic compounds. The PF4 IgG kit contains all of the reagents necessary to perform the assay.

The Immucor GTI Diagnostics, Inc. PF4 IgG assay is a qualitative screening assay for the detection of heparin-associated IgG antibodies in human serum or plasma, commonly found in patients with Heparin Induced Thrombocytopenia (HIT). The device is a Class II medical device, product code LCO.

This 510(k) submission is for modifications to a previously cleared device (K071781) and includes: a change in the Positive Serum Control raw material, the addition of plasma as a sample type, and a change in the Stopping Solution.

1. Table of acceptance criteria and reported device performance:

2. Sample size used for the test set and the data provenance:

• Positive Serum Control Raw Material Change (Precision Study):
  • No specific "test set" sample size for patient samples is provided. The study focused on the performance of the new positive serum control material within the assay.
  • The study used a single lot of the PF4 IgG kit and three validation lots of the Positive Serum Control.
  • Data provenance is internal, generated as part of process validation.
• Addition of Plasma as a Sample Type:
  • Test set size: 174 frozen serum and plasma samples.
  • Data provenance: Samples obtained from Florida Hospital for an internal study. Retrospective, as samples were frozen.
  • Sub-study for ACD/Sodium Citrate vs. Serum: Blood collected from 24 individuals. Origin not specified beyond "internal study." Retrospective.
• Stopping Solution Change:
  • Test set size: No patient samples explicitly mentioned in the summary for the Stopping Solution evaluation itself. The testing involved comparing the performance of the new Stopping Solution with the predicate using various assay components and a QC panel.
  • QC Panel: 21 positive samples and 24 negative samples.
  • Data provenance: Internal, generated as part of lot-to-lot comparison and process validation.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

The document does not provide information on the number or qualifications of experts used to establish ground truth for the test sets. For the plasma sample type study, it states 174 frozen serum and plasma samples were used, and for the ACD/Sodium Citrate comparison, blood was collected from 24 individuals "known to be PF4: heparin antibody negative." How this "known" status was established (e.g., by experts, by a predicate device, by clinical diagnosis) is not detailed. The ground truth for the QC panel used in the stopping solution study is based on "expected qualitative result," implying pre-characterized samples, not expert consensus at the time of the study.

4. Adjudication method for the test set:

The document does not describe any adjudication method for establishing ground truth for the test sets. The studies appear to rely on the inherent reactivity of the samples (e.g., "known to be PF4: heparin antibody negative," "high level reacting anti:PF4 heparin antibody sample," "expected qualitative result" for QC panels).

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:

This device is an in vitro diagnostic (IVD) assay, specifically an ELISA. It is not an AI-assisted diagnostic tool that involves human readers interpreting images or data. Therefore, an MRMC comparative effectiveness study involving human readers and AI assistance is not applicable and was not performed.

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

The device is an IVD assay, not an algorithm. Its performance is evaluated biochemically based on optical density measurements, which are then interpreted qualitatively (positive/negative) according to the assay's cut-offs. The studies described are standalone performance evaluations of the modified assay components and sample compatibility.

7. The type of ground truth used:

• For the plasma sample type comparison, the ground truth appears to be based on the qualitative results obtained from the serum sample, as the goal was to demonstrate equivalence between serum and plasma samples. For the sub-study on ACD/Sodium Citrate, it refers to individuals "known to be PF4: heparin antibody negative" and "high level reacting anti:PF4 heparin antibody sample," indicating pre-characterized samples.
• For the stopping solution change, the ground truth for the QC panel was based on "expected qualitative result," implying pre-defined and characterized positive and negative samples.
• The primary ground truth for the assay itself (predicate and candidate) would typically be established against either clinical diagnosis of HIT (outcome data) or a well-established reference method, but this is not explicitly detailed for these specific modification studies. The studies focus on demonstrating that the modifications do not adversely affect the device's performance compared to its previous state.

8. The sample size for the training set:

The document does not describe a training set as this is not an algorithm requiring machine learning. The studies are performance and validation studies for changes to an IVD assay.

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

Not applicable, as there is no training set for this type of device.

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