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Puritan PurSafe Plus Collection and Transport System is an enclosed system intended for the collection, inactivation, and preservation of human upper respiratory specimens suspected of containing SARS-CoV-2. Puritan PurSafe Plus Collection and Transport System can be used for collection, transport, and storage of specimens at 2-4°C and 25-30°C. Specimens collected and stored in the PurSafe Plus Collection and Transport System are suitable for use with legally marketed molecular diagnostic devices.

Device Description

Puritan PurSafe Plus Collection and Transport System is comprised of a peel pouch containing a sterile polyester flock swab applicator for collecting clinical specimens and a polypropylene vial containing 1mL PurSafe Plus buffer. PurSafe Plus MK buffer ensures stability of Sars Cov-2 during sample transport/storage at refrigerated to ambient temperature (4-30°C) and is intended to inactivate Sars Cov-2.

AI/ML Overview

Acceptance Criteria and Device Performance Study for Puritan PurSafe Plus Collection and Transport System

This document outlines the acceptance criteria and reports on the study that demonstrates the Puritan PurSafe Plus Collection and Transport System meets these criteria, based on the provided FDA 510(k) clearance letter.

1. Table of Acceptance Criteria and Reported Device Performance

Acceptance Criteria Category	Specific Criteria	Puritan PurSafe Plus Performance
Limit of Detection (LOD)	The device should not adversely affect the stated detection limits of the downstream molecular diagnostic device for SARS-CoV-2 viral RNA. Specifically, it should achieve positive detection at an estimated concentration of 64 genome copies/mL when used with the Cepheid GeneXpert® IV system (Xpert Xpress Cov-2/Flu/RSV).	Met. The study indicated positive detection of viral RNA at an estimated concentration of 64 genome copies/mL using the Cepheid GeneXpert® IV system. Quantitative droplet digital PCR showed no significant loss of detection for samples stored in Nasal + PurSafe Plus compared to just nasal matrix alone. No significant differences in SARS-CoV-2 RNA positive detection were observed among PurSafe lots and the predicate Zymo product. Additionally, 20 replicates at the LOD concentration (64 genome copies/mL) over six days yielded positive detection for all replicates, with Ct values within 2 units.
SARS-CoV-2 RNA Stability	The device should preserve SARS-CoV-2 RNA for up to 28 days at temperatures of 4°C and 30°C, demonstrating no significant loss in the ability to positively detect SARS-CoV-2 using the Cepheid GeneXpert® IV system.	Met. For all three Puritan lots and the Zymo lot, samples stored at 4°C and 30°C for up to 28 days showed no significant loss in the ability to positively detect SARS-CoV-2. Mean Ct values for all samples across all time points and temperatures were less than 3 Ct units from baseline. All Puritan lots were found to be equivalent to the Zymo product in preservation of SARS-CoV-2 RNA.
Viral Inactivation	The device's buffer should be able to inactivate SARS-CoV-2 virus after exposure.	Met. SARS-CoV-2 virus was inactivated after exposure to three different lots of Puritan PurSafe Plus buffer (at 1:0 dilution) after a minimum of 1 minute of exposure. Cytotoxicity was observed at a 1/10 dilution of the buffer but not at 1/60, informing subsequent inactivation study dilutions.

2. Sample Size and Data Provenance

Test Set Sample Size:
- LOD Study: N=24 for the initial assessment (6 concentrations x 2 replicates x 2 lots). N=20 for the confirmatory LOD (20 replicates at 64 genome copies/mL).
- Stability Study: N=72 (4 lots x 5 time points x 2 incubation temperatures x 2 replicates).
Data Provenance: The data was generated using heat-inactivated SARS-CoV-2 virus (BEI Resources; ATCC # VR-1986HK) spiked into clinically negative human nasal matrix (Lee Biosolutions, Maryland Heights, MO). This suggests retrospective analysis on a prepared sample matrix rather than prospective patient samples. The country of origin of the data is not explicitly stated, but the vendors for the virus and nasal matrix are US-based.

3. Number of Experts and Qualifications for Ground Truth

The document does not mention the use of human experts to establish ground truth for the performance studies.
The ground truth for the studies was based on the known concentration of spiked heat-inactivated SARS-CoV-2 virus and the analytical performance of the Cepheid GeneXpert® IV system and droplet digital PCR.

4. Adjudication Method for the Test Set

No adjudication method is described. The studies rely on quantitative measurements of viral RNA detection using laboratory instruments (Cepheid GeneXpert® IV and ddPCR) and direct observation of viral inactivation.

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

No MRMC comparative effectiveness study was done. This device is a collection and transport system, not an interpretive diagnostic AI algorithm that would typically involve human readers. Therefore, the effect size of human readers improving with or without AI assistance is not applicable.

6. Standalone Algorithm Performance Study

A standalone performance study was done. The studies described (LOD, Stability, Inactivation) assess the performance of the Puritan PurSafe Plus Collection and Transport System (the "device" or "algorithm" in this context) directly, without human interpretation or intervention in the diagnostic process beyond laboratory procedures. The system's ability to preserve and inactivate the virus, and not interfere with downstream molecular detection, is evaluated independently.

7. Type of Ground Truth Used

The type of ground truth used was analytical ground truth and virological ground truth.
- Analytical Ground Truth: For the LOD and Stability studies, known concentrations of heat-inactivated SARS-CoV-2 (quantified in genome copies/mL) were spiked into confirmed clinically negative nasal matrix. The expected outcome was the detection of this known concentration by the downstream molecular diagnostic device.
- Virological Ground Truth: For the Inactivation study, the presence or absence of viable SARS-CoV-2 virus after exposure to the buffer was the ground truth, assessed by exposing VeroE6 cells to the treated virus.

8. Sample Size for the Training Set

The document does not specify a training set sample size. This is because the device is a physical collection and transport system, not an AI or machine learning model that typically requires a separate training set. The performance studies described are for validation, not model training.

9. How Ground Truth for the Training Set Was Established

As there is no explicit training set for an AI/ML model, the concept of establishing ground truth for a training set is not applicable to this device. The ground truth described in point 7 is for the validation of the device's functional performance.

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