(255 days)
The eSensor® Warfarin Sensitivity Saliva Test is an in vitro diagnostic test for the detection and genotyping of the *2 and *3 alleles of the cytochrome P450 (CYP450) 2C9 gene locus and the Vitamin K epoxide reductase C1 (VKORC1) gene promoter polymorphism (-1639G>A) from genomic DNA of human saliva samples collected using the Oragene® Dx Device, as an aid in the identification of patients at risk for increased warfarin sensitivity.
The eSensor® Warfarin Sensitivity Saliva Test is a multiplex microarray-based genotyping test system. It is based on the principles of competitive DNA hybridization using a sandwich assay format, wherein a single-stranded target binds concurrently to sequence-specific solution-phase signal probe and solid-phase electrode-bound capture probe. The test employs polymerase chain reaction amplification, exonuclease digestion and hybridization of target DNA. In the process, the double stranded PCR amplicons are digested with exonuclease to generate single stranded DNA suitable for hybridization. Hybridization occurs in the eSensor XT-8 Cartridge (described below) where the singlestranded target DNA is mixed with a hybridization solution containing labeled signal probes.
During hybridization, the target DNA binds to a complementary, single-stranded capture probe immobilized on the working electrode surface. Single-stranded signal probes (labeled with electrochemically active ferrocenes) bind to the target adjacent to the capture probe. When inserted into the eSensor XT-8 instrument (described below), simultaneous hybridization of target to signal probes and capture probe is detected by alternating current voltammetry (ACV). Each pair of working electrodes on the array contains a different capture probe, and sequential analysis of each electrode allows genotyping of multiple mutations or polymorphisms.
The Assay Cartridge (eSensor XT-8 Cartridge): The eSensor XT-8 cartridge device consists of a printed circuit board (PCB) with a multi-layer laminate and a plastic cover that forms a hybridization chamber has a volume of approximately 140 µl. The cartridge consists of a diaphragm pump and check valves (microfluidic components) that circulate the hybridization solution in the hybridization chamber when inserted into the eSensor XT-8 instrument. The PCB chip consists of an array of 72 gold-plated working electrodes, a silver/silver chloride reference electrode, and two gold-plated auxiliary electrodes. Each working electrode has a connector contact pad on the opposite side of the chip for electrical connection to the eSensor XT-8 instrument. Each electrode is modified with a multicomponent, self-assembled monolayer that includes presvnthesized oligonucleotide capture probes specific for each polymorphic site on the test panel and insulator molecules. The cartridge also contains an electrically erasable programmable read-only memory component (EEPROM) that stores information related to the cartridge (e.g., assay identifier, cartridge lot number, and expiration date).
The eSensor XT-8 Instrument (Same as cleared under K073720): The eSensor XT-8 is a clinical multiplex instrument that has a modular design consisting of a base module and one, two, or three cartridge-processing towers containing 8, 16, or 24 cartridge slots, respectively. The cartridge slots operate independently of each other. Any number of cartridges can be loaded at one time, and the remaining slots are available for use while the instrument is running. The base module controls each processing tower, provides power, and stores and analyzes data. The base module includes the user interface, and a 15-in. portrait-orientation display and touch panel. The instrument is designed to be operated solely with the touch screen interface. Entering patient accession numbers and reagent lot codes can be performed by the bar code scanner, the touch screen, or uploading a text file from a USB memory stick. Each processing tower consists of eight cartridge modules, each containing a cartridge connector, a precision-controlled heater, an air pump, and electronics. The air pumps drive the diaphragm pump and valve system in the cartridge, eliminating fluid contact between the instrument and the cartridge. The pneumatic pumping enables recirculation of the hybridization solution allowing the target DNA and the signal probes to hybridize with the complementary capture probes on the electrodes. The diaphragm pump in the cartridge is connected to a pneumatic source from the eSensor XT-8 instrument and provides unidirectional pumping of the hybridization mixture through the microfluidic channel during hybridization. Using microfluidic technology to circulate the hybridization solution minimizes the unstirred boundary layer at the electrode surface and continuously replenishes the volume above the electrode that has been depleted of complementary targets and signal probes. The XT-8 instrument provides electrochemical detection of bound signal probes by ACV and subsequent data analysis and test report generating functions. All hybridization, ACV scanning and analysis parameters are defined by a scanning protocol loaded into the XT-8 Software, and then specified for use by the EEPROM on each cartridge.
The Assay Kit: The Warfarin Sensitivity Saliva Test consists of the test cartridge and the following components: 1) PCR REAGENTS consisting of: PCR Mix [PCR buffer containing primers and dNTP mixture (dCTP, dGTP, dATP, and dUTP)], MgCl2 thermostable DNA polymerase (Taq Polymerase ); and 2 GENOTYPING REAGENTS consisting of: lambda exonuclease, signal probes and hybridization buffer ingredients (Buffer-1 and Buffer-2).
Here's a breakdown of the acceptance criteria and the study details for the eSensor® Warfarin Sensitivity Saliva Test, based on the provided document:
Acceptance Criteria and Device Performance
The acceptance criteria are implied by the comparison to DNA sequencing, which is considered the gold standard for genotyping. The device performance is reported as agreement percentages with DNA sequencing.
| Characteristic | Acceptance Criteria (Implied) | Reported Device Performance (After Retest) |
|---|---|---|
| *CYP450 2C9 2 Allele Genotyping | High agreement with DNA sequencing | |
| 2C9 wt/wt Agreement | - | 100.0% (95% LCB: 98.7%) |
| 2C9 wt/*2 Agreement | - | 98.6% (95% LCB: 93.4%) |
| 2C9 *2/*2 Agreement | - | 100.0% (95% LCB: 71.7%) |
| *CYP450 2C9 3 Allele Genotyping | High agreement with DNA sequencing | |
| 2C9 wt/wt Agreement | - | 99.3% (95% LCB: 97.8%) |
| 2C9 wt/*3 Agreement | - | 100.0% (95% LCB: 91.6%) |
| 2C9 *3/*3 Agreement | - | 100.0% (95% LCB: 36.8%) |
| VKORC1 Genotyping | High agreement with DNA sequencing | |
| VKORC1 G/G Agreement | - | 100.0% (95% LCB: 97.6%) |
| VKORC1 G/A Agreement | - | 100.0% (95% LCB: 97.8%) |
| VKORC1 A/A Agreement | - | 100.0% (95% LCB: 95.3%) |
| Interference Study | 100% agreement with DNA sequencing | |
| Endogenous Interfering Substances (Control, Amylase, Hemoglobin, IgA, Total Protein) | 100% agreement | 100% agreement for all substances |
| Exogenous Interfering Substances (Eating, Drinking, Chewing Gum, Mouthwash, Smoking) | 100% agreement | 100% agreement for all activities |
Note: The document implies acceptance criteria by comparing the device's performance to DNA sequencing, which is implicitly considered the standard for accuracy. Specific numeric thresholds for "acceptance" are not explicitly stated, but the high agreement percentages (mostly 100%) and the lower bounds of the 95% confidence intervals (LCB) suggest a requirement for high concordance.
Study Information
2. Sample Size Used for the Test Set and Data Provenance:
- Sample Size: A total of 316 gDNA samples were extracted from saliva specimens for the method comparison study.
- Data Provenance: The document does not explicitly state the country of origin or if the data was retrospective or prospective. It uses "saliva specimen" without further context on donor recruitment or source.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts:
- Experts: Not applicable. The "ground truth" for the genotyping results was established by DNA sequencing, not by human experts.
- Qualifications: Not applicable.
4. Adjudication Method for the Test Set:
- Adjudication Method: Not applicable in the traditional sense of human consensus. The reference method (ground truth) was DNA sequencing. The study reports "No-Calls" and "Miscalls" by the eSensor® device when compared to DNA sequencing. The "After Retest" results suggest that initial "No-Calls" were re-evaluated and resolved, leading to higher agreement.
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:
- MRMC Study: No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This device is an in-vitro diagnostic (IVD) for genotyping, which is an automated process, not an imaging device requiring human interpretation alongside AI.
6. If a Standalone (i.e. algorithm only without human-in-the loop performance) was done:
- Standalone Performance: Yes, the performance reported is essentially a standalone (algorithm only) performance. The eSensor® Warfarin Sensitivity Saliva Test is an automated system that generates results which are then compared to DNA sequencing, without human-in-the-loop interpretation being part of the primary performance evaluation.
7. The Type of Ground Truth Used:
- Ground Truth Type: DNA sequencing (referred to as "bidirectional DNA sequencing" or "DNA Sequencing Result"). This is considered a gold standard for genetic polymorphism detection.
8. The Sample Size for the Training Set:
- Training Set Sample Size: The document does not specify a separate training set. For IVD devices, especially those based on established molecular biology principles, the "training" (development) often involves optimizing reagents and protocols, rather than machine learning algorithm training with distinct datasets. The method comparison study appears to be the primary validation of the device's performance against a reference method.
9. How the Ground Truth for the Training Set was Established:
- Training Set Ground Truth: As no explicit training set is mentioned in the context of machine learning, this question is not directly applicable. For the performance validation, as stated above, DNA sequencing was used as the ground truth.
§ 862.2570 Instrumentation for clinical multiplex test systems.
(a)
Identification. Instrumentation for clinical multiplex test systems is a device intended to measure and sort multiple signals generated by an assay from a clinical sample. This instrumentation is used with a specific assay to measure multiple similar analytes that establish a single indicator to aid in diagnosis. Such instrumentation may be compatible with more than one specific assay. The device includes a signal reader unit, and may also integrate reagent handling, hybridization, washing, dedicated instrument control, and other hardware components, as well as raw data storage mechanisms, data acquisition software, and software to process detected signals.(b)
Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 862.9. The special control is FDA's guidance document entitled “Class II Special Controls Guidance Document: Instrumentation for Clinical Multiplex Test Systems.” See § 862.1(d) for the availability of this guidance document.