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The HealthTEST® Heparin/Platelet Factor 4 Antibody Assay is an in vitro diagnostic device designed for the detection of antibodies to Platelet Factor 4 complexed to polyanionic compounds such as polystyrene. These antibodies are found in some patients undergoing heparin therapy.

The HEALTHTEST® Heparin/Platelet Factor 4 Antibody Assay is a qualitative in vitro diagnostic device designed for the detection of antibodies to the Platelet Factor 4 complexed to polyanionic compounds such as polystyrene. These antibodies are found in some patients undergoing heparin therapy.

The risk of heparin induced thrombocytopenia (HIT) is greatly increased in patients with recent exposure to heparin. The presence of heparin/PF-4 antibody is associated with patients arisk. for HIT, and is rapidly becoming a standard of care in hematology and cardinlogy. The need for a rapid test to detect these antibodies from serum or plasma in less than 5 minutes is highly desired. This rapid manual assay should be easily performed when STAT results are required,

The HealthTEST® Heparin/Platelet Factor 4 Antibody Assay consists of two components: a Mini-reactor device containing a membrane filtration system and a results window, and a dispenser containing reaction reagents.

The Mini-reactor contains a reaction well that allows the sample to react with the reagents. The sample is added to the reaction well followed by the reagents contained in the reagent dispenser. The reagents contain microparticles coated with purified PF-4 protein as well as additional enhancing agents designed to promote rapid agglutination of the particles in the presence of specific antibodies in the test sample.

Once the reagents have reacted with the sample in the reaction well, the reaction mixture automatically collects over the membrane filtration system. This system acts to filter agglutinated particles, while allowing non-agglutinated particles to pass through. Thus, an agglutinated, reactive sample will be trapped within the membrane. Since the dyed particles are trapped by this filter, no particles and hence no color, are able to migrate past the positive/negative line on the results window. Conversely, a nonagglutinated, non-reactive sample will pass through the membrane filter and into the wicking layers, and no color will migrate past the positive/negative line.

Here's a breakdown of the acceptance criteria and study information for the HealthTEST® Heparin/Platelet Factor 4 Antibody Assay:

1. Table of Acceptance Criteria and Reported Device Performance

Note: The acceptance criteria are "implied" because they are not explicitly stated as numerical targets. Instead, the submission demonstrates "substantial equivalence" to the predicate device by showing comparable or superior performance, particularly in specificity. The lower sensitivity in both plasma and serum for the HealthTEST® device compared to the predicate's serum sensitivity is noted but not deemed to raise new issues of safety and effectiveness.

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

• Study #1 (Plasma):
  • Total Samples: 175
  • Data Provenance: Fresh samples originating from "field sources." No specific country of origin is mentioned. The study is retrospective in that samples were collected and then tested, but the "fresh samples" suggest they were not archival.
• Study #2 (Serum):
  • Total Samples: 179
  • Data Provenance: Fresh samples originating from "field sources." No specific country of origin is mentioned. The study is retrospective in that samples were collected and then tested, but the "fresh samples" suggest they were not archival.

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

The ground truth was established by comparing the HealthTEST® device's results to a "commercially available, standard laboratory method" which is identified as the GTI PF4 Elisa Assay (K983379). It is implicit that the results from this predicate ELISA assay were considered the reference standard or "ground truth" for the comparison studies. No individual experts were used for adjudication of the test results themselves; the ELISA outcome was the benchmark.

4. Adjudication Method for the Test Set

No explicit human adjudication method (e.g., 2+1, 3+1) was used for the test set. The HealthTEST® device's results were directly compared against the results of a single reference method, the GTI PF4 Elisa Assay.

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

No MRMC comparative effectiveness study was described. This device is an in vitro diagnostic assay, where the output is directly generated by the device based on a chemical reaction, rather than being interpreted by human readers.

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

Yes, the described studies are standalone performance evaluations. The specificity and sensitivity percentages are for the device (HealthTEST® Heparin/Platelet Factor 4 Antibody Assay) itself, without human interpretation of the results beyond reading the positive/negative line on the device.

7. Type of Ground Truth Used

The ground truth used was based on the results from a predicate laboratory assay (GTI PF4 Elisa Assay). This is a form of comparative gold standard where a well-established and legally marketed diagnostic device's results are used as the benchmark.

8. Sample Size for the Training Set

The document does not provide information on a specific "training set" for the HealthTEST® Heparin/Platelet Factor 4 Antibody Assay. Diagnostic assays like this often undergo an extensive development and optimization phase, but the presented data focuses on performance verification (test set) against a predicate, rather than a separate training and validation split as might be seen with AI/machine learning models.

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

As no explicit training set is mentioned for the HealthTEST® device itself (it's a chemical assay rather than a predictive algorithm in the modern AI sense), the concept of "ground truth for the training set" as it applies to AI models is not directly applicable here. The development of such assays typically involves iterative formulation and testing, where the "ground truth" in development would stem from clinical diagnosis or an accepted reference method, guiding the optimization of the assay's reagents and detection mechanism.

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