(210 days)
Cell-Free DNA BCT is a direct-draw venous whole blood collection device intended for the collection, and transport of venous whole blood samples for use in conjunction with cell-free DNA next-generation sequencing liquid biopsy assays that have been cleared or approved for use with samples collected in the Cell-Free DNA BCT device.
Cell-Free DNA BCT is a sterile, single use, direct-draw blood collection tube comprised of 3 components (i.e. glass tube with rubber stopper, anticoagulant, and cell preservatives). The blood collection tube manufactured with USP Type III glass containing cerium oxide (to prevent color change associated with gamma irradiation). Each tube includes 200 uL ± 10% of liquid reagent composition includes an anticoagulant K3EDTAand a preservative.
The device is intended to be placed inside a tube holder or an adaptor that contains a needle designed to pierce the tube closure and allow blood to flow into the tube. Once the vein has been penetrated blood collection needle or a blood collection set), the tube is pushed into the holder, and the blood enters the tube. Once a tube has drawn the appropriate amount of blood (10 mL), it is disengaged from the holder and inverted 10 times to mix the blood. The specimen is then transported to the lab for plasma isolation and extraction of cfDNA.
This response describes the acceptance criteria and study details for the Cell-Free DNA BCT device, as outlined in the provided text.
Acceptance Criteria and Device Performance
The provided document does not explicitly present a consolidated table of acceptance criteria with corresponding reported device performance for all studies. Instead, acceptance is implied through successful outcomes of various analytical performance studies. The core acceptance criteria revolve around the ability of the Cell-Free DNA BCT to preserve cfDNA concentration, size, and integrity, and to maintain variant call concordance (Positive Percent Agreement - PPA and Negative Percent Agreement - NPA) in comparison to a reference or within defined variations. Specific numerical acceptance thresholds are often redacted (marked as "(b) (4)") in the provided text.
Here’s a table summarizing the reported device performance based on the described studies, with acceptance implied by the positive conclusions of the FDA.
| Study Category | Specific Study | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|---|
| Analytical Performance | |||
| Repeatability | Within-lot (between tube) variability | High Average Positive Agreement (APA) and Average Negative Agreement (ANA) for variant calls. | APA and ANA calculated, with specific numerical values redacted as (b) (4). The study concludes that variability was evaluated. |
| Reproducibility | Lot-to-lot variability | High APA and ANA between different lots. | APA and ANA calculated for lot comparisons, with specific numerical values redacted as (b) (4). |
| Shelf-life | Device performance over time (24.5 months) and temperature (2-30°C) | Maintenance of cfDNA concentration, size, and integrity. | Supports that devices stored at 2-30°C for 18.5 months prior to blood collection are able to maintain cfDNA concentration and integrity when blood specimens are stored for up to 8 days after blood collection. |
| Additional Studies | Robustification, draw volume, stopper closure, stopper pullout, stopper resealing, anticoagulant effectiveness | Study protocols, acceptance criteria, and results considered acceptable. | Protocols, acceptance criteria, and results "were provided and found to be acceptable." |
| Analytical Specificity | Preservative interference | High PPA and NPA for variant call concordance when preservative concentration is varied. | Results confirmed that increasing either component of the preservative does not interfere with the ability of the Cell-Free DNA BCT to preserve cfDNA suitable for assay performance. Specific numerical values redacted as (b) (4). |
| Incomplete Mixing (5 vs 10, 15 vs 10 inversions) | High PPA and NPA for variant call concordance compared to 10 inversions standard. | Results indicated inadequate or overmixing may result in diminished performance. Specific numerical values redacted as (b) (4). This suggests 10 inversions is the validated standard. | |
| Short Draw (underfilling the tube) | High PPA and NPA compared to full draw. | Results indicated that underfilling with less than 5 mL of blood may lead to poor product performance. A precaution has been added to labeling. Specific numerical values redacted as (b) (4). | |
| Tube Stopper Extractables | No interaction with patient specimens that interferes with cfDNA preservation. | Results support that extractables are not anticipated to interfere with device performance. | |
| Specimen Stability | cfDNA Stability (device aged 1-17 months) | High PPA and NPA between reference (youngest lot) and test conditions (older lots). | Results support that cfDNA isolated from the device is of sufficient quantity, quality, and integrity for the intended downstream application throughout the life of the device. Specific numerical values redacted as (b) (4). |
| Post-Collection Storage of Venous Whole Blood (up to 7 days) | Preservation of cfDNA specimen concentration and integrity compared to K2EDTA. | Demonstrated that the candidate device preserves cfDNA concentration and integrity better than K2EDTA tubes when stored for up to 8 days. Specific numerical values redacted as (b) (4). | |
| Pre-collection storage (2-30°C) and Post-collection storage (D1 vs D7) impacts on Guardant360 CDx assay performance | High APA and ANA between varied pre-collection storage conditions and post-collection storage durations. | Results demonstrate that storage of whole blood specimens for up to 7 days and BCTs at 2-30°C prior to collection does not impact Guardant Health Guardant360 CDx assay performance. Specific numerical values redacted as (b) (4). | |
| Comparison Studies | |||
| Method Comparison | Cell-Free DNA BCT vs. K2EDTA BCT Concordance | High PPA and NPA with K2EDTA BCTs (used in predicate device clinical studies). Acceptable delta PPA and delta NPA values. | K2EDTA tubes and Cell-Free DNA BCTs demonstrated expected levels of positive agreement, PPA (b) (4), and negative agreement, NPA (b) (4). Discordant detection was observed below LoD, with agreement above LoD being (b) (4). Delta PPA and delta NPA values were within acceptable limits. |
Study Details
2. Sample Size Used for the Test Set and Data Provenance
- Repeatability (Within-lot variability): 33 patients with advanced stage solid tumors. Each subject provided blood for 4 Cell-Free DNA BCTs from a single lot. Prospective data collection.
- Reproducibility (Lot-to-lot variability): 30 patients with advanced stage solid tumors. Blood was drawn into Cell-Free DNA BCTs representing 3 different lots. Prospective data collection.
- Shelf-life: 30 healthy subjects. Blood collected into tubes tested at various timepoints (T0, T8.5, T12.5, T18.5, T24.5 months) and pre-collection storage temperatures (2, 22, or 30°C). Prospective data collection.
- Preservative interference: 12 subjects with advanced stage solid tumors. Three venous whole blood specimens collected into candidate devices (reference, 2x Preservative A, 2x Preservative B). Prospective data collection.
- Incomplete Mixing: Patients with advanced stage solid tumors (specific number not given, but likely similar to other studies, potentially 12 from context of preservative study). Three Cell-Free DNA BCTs per subject (10, 5, or 15 inversions). Prospective data collection.
- Short Draw: 15 subjects with advanced stage solid tumors. Three Cell-Free DNA BCTs per subject, reflecting normal, 2x Reagent (5mL blood), or (b)(4) Reagent ((b)(4) blood) fill volumes. Prospective data collection.
- cfDNA Stability (device aged): Patients with advanced stage solid tumors (specific number not given). Four Cell-Free DNA BCTs per patient (two reference from youngest lot, one from 8 months, one from 17 months post-manufacture). Prospective data collection.
- Post-Collection Storage of Venous Whole Blood: 30 healthy subjects. Eight tubes per donor (4 K2EDTA, 4 Cell-Free DNA BCTs) tested under various storage conditions (Day 0 immediate, Day 7 at (b)(4) or (b)(4)). Prospective data collection.
- Pre-collection storage and Post-collection storage impacts on Guardant360 CDx assay performance: Whole blood specimens from patients with advanced stage solid tumors (specific number not given). Cell-Free DNA BCTs manufactured at various time points (T0, T3.2, T7.2, T12.2, T18.2, T24.2 months) and BCTs stored at extreme temperatures before collection. Plasma isolated after 1 or 7 days post-collection. Prospective data collection.
- Cell-Free DNA BCT vs. K2EDTA BCT Concordance: 59 patients (non-small cell lung cancer Stage III or IV, pre-screened for CDx variants). Two K2EDTA BCTs and two Cell-Free DNA BCTs collected per patient. Three tubes were processed for the study (one K2EDTA, two Cell-Free DNA BCTs). Prospective data collection. All data appears to be US (country of origin for Guardant Health) and primarily prospective, involving clinical subjects or healthy donors for specific studies.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not explicitly state the number or qualifications of experts used to establish ground truth. For studies involving variant call concordance, the "ground truth" for the performance metrics (PPA, NPA, APA, ANA) would be derived from the Guardant360 CDx assay (P200010), which is a cleared/approved next-generation sequencing liquid biopsy assay. The internal analysis of these assay results would be performed by qualified laboratory personnel at Guardant Health, but "experts" in the sense of independent clinical reviewers for ground truth are not mentioned as part of these specific analytical studies. The ground truth is the molecular profile determined by the Guardant360 CDx assay itself.
4. Adjudication Method for the Test Set
Adjudication methods for establishing ground truth from multiple readers/methods are not applicable (N/A) in this context. The "ground truth" for each specific experiment is defined by the results obtained from the reference condition or the established Guardant360 CDx assay. Variant call agreements (PPA, NPA, APA, ANA) are calculated by comparing results from different conditions to each other or to a pre-defined reference condition within the study design, not by external expert adjudication of conflicting results.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was described. This device is a blood collection tube, and the studies focus on its analytical performance and impact on downstream assay results, not on human reader interpretation of diagnostic images or data. The impact is assessed on the molecular analysis carried out by the Guardant360 CDx assay.
6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study
Yes, all presented performance studies are "standalone" in the sense that they evaluate the analytical performance of the device (Cell-Free DNA BCT) in preserving cfDNA and enabling accurate results from the Guardant360 CDx assay. The performance metrics (PPA, NPA, APA, ANA, cfDNA concentration, integrity) are objective measurements derived from the molecular assay, not contingent on human interpretation in the loop with the device itself. The Guardant360 CDx assay itself is an "algorithm only" type of test in that its result is a molecular profile.
7. Type of Ground Truth Used
The primary type of "ground truth" used across these studies is the molecular profile/variant calls generated by the Guardant360 CDx assay (P200010).
- For repeatability and reproducibility, variant calls from replicate tubes serve as a comparison point.
- For preservative, mixing, and short draw interference studies, variant calls from a reference condition (e.g., normal preservative, 10 inversions, full draw) serve as the ground truth against which experimental conditions are compared using PPA and NPA.
- For shelf-life and cfDNA stability studies, cfDNA concentration, size, integrity, and variant call concordance (PPA/NPA) against a Day 0 or youngest-lot reference are used.
- For method comparison, concordance is established against the K2EDTA BCT, which was used to acquire samples for the clinical studies supporting Guardant360 CDx. This implies K2EDTA's performance is currently accepted, making it a de-facto reference.
8. The Sample Size for the Training Set
The document describes performance evaluation studies and does not mention "training sets" as it would for a typical AI/ML algorithm development. This device is a blood collection tube with specific chemical and physical properties aimed at sample preservation, not a diagnostic algorithm that requires training. Therefore, N/A for training set sample size.
Given that the performance is assessed using the Guardant360 CDx assay, it can be inferred that the assay itself would have its own extensive training and validation datasets, but these are not for the Cell-Free DNA BCT device specifically.
9. How the Ground Truth for the Training Set Was Established
As noted above, there is no "training set" for the Cell-Free DNA BCT device. The performance is based on analytical studies. N/A.
§ 862.1676 Blood collection device for cell-free nucleic acids.
(a)
Identification. A blood collection device for cell-free nucleic acids is a device intended for medical purposes to collect, store, transport, and handle blood specimens and to stabilize and isolate cell-free nucleic acid components prior to further testing.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Design verification and validation documentation must include appropriate design inputs and design outputs that are essential for the proper functioning of the device for its intended use, including all of its indications for use, and must include the following:
(i) Documentation demonstrating that appropriate, as determined by FDA, measures are in place (
e.g., validated device design features and specifications) to ensure that users of blood collection device for cell-free nucleic acids devices are not exposed to undue risk of bloodborne pathogen exposure and operator injury during use of the device, including blood collection, transportation, and centrifugation processes.(ii) Documentation demonstrating that appropriate, as determined by FDA, measures are in place (
e.g., validated device design features and specifications) to ensure that the device reproducibly and reliably collects, transports, stabilizes, and isolates cell-free nucleic acids of sufficient yield and quality suitable for downstream applications as appropriate for its intended use. At a minimum, these measures must include:(A) Data demonstrating that blood samples collected in the device have reproducible cell-free nucleic acid yields that are suitable, as determined by FDA, for downstream testing as appropriate for the intended use, including estimates of within-lot, within-device, and lot-to-lot variability;
(B) Data demonstrating that cell-free nucleic acid yields isolated from blood specimens collected into the device do not add clinically significant bias to test results obtained using the downstream application(s) described in the intended use. For devices indicated for use with multiple downstream applications, data demonstrating acceptable performance for each type of claimed use or, alternatively, an appropriate, as determined by FDA, clinical justification for why such data are not needed;
(C) Data demonstrating that the device appropriately stabilizes cell-free nucleic acids after sample collection, during storage, and during transport over the claimed shelf life of the device;
(D) Data demonstrating that samples collected in the device have minimal levels of contamination with other types of nucleic acids present in cells or cellular components, and that these levels of contamination do not interfere with downstream testing;
(E) Data from analytical or clinical studies that demonstrate that, when used as intended, the device consistently draws a blood sample volume that is within the indicated fill range;
(F) Data from analytical or clinical studies that demonstrate that, when used as intended, cell-free nucleic acid yield, stability, and quality are not significantly impacted by interference due to other parts of the device (such as reduced or excess active ingredient) or specimen collection and processing procedures (such as hemolysis, centrifugation, or mixing of blood with anticoagulant or additives); and
(G) Data from analytical studies that demonstrate that the device is suitable for its intended use across all storage and sample handling conditions described in the device labeling, including device shelf life and shipping conditions (
e.g., temperature, humidity, duration).(iii) A protocol, reviewed and determined acceptable by FDA, that specifies the verification and validation activities that will be performed for anticipated device modifications to reevaluate performance claims or performance specifications. This protocol must include a process for assessing whether a modification to technology, engineering, performance, materials, specifications, or indications for use, or any combination thereof, could significantly affect the safety or effectiveness of the device. The protocol must include assessment metrics, acceptance criteria, and analytical methods for the performance testing of changes.