(231 days)
The microlNR System measures prothrombin time (PT) expressed in International Normalized Ratio (INR), for monitoring oral anticoagulant therapy with warfarin.
The microINR System consists of a microINR Meter and microINR Chip and uses fresh capillary whole blood from a fingerstick.
The microINR System is intended for patient self-testing use as well as for healthcare professionals at Point of Care settings.
The microlNR System is intended for use in patients 18 years old or older. Patients must be stable on warfarin medication for at least 6 weeks before starting to use the microINR System.
For Self-testing use: The System is intended for properly trained users under specific prescription of a physician. Caution: The microINR System is not in patients who are transitioning from heparin treatment to VKA therapy. The microINR System is not intended to be used for screening purposes.
The microINR® System is comprised of a portable measuring device (microINR® Meter) and test strips (microINR® Chips) in which the capillary blood sample flows through capillary action.
The microINR® Chip contains a reagent in dried form which consists of thromboplastin, and contains two symmetrical regions, the measuring channel and a control channel. The microINR® Meter measures International Normalized Ratio (INR) based on a Prothrombin Time (PT) assay carried out in the microINR® Chip based on microfluidic technology with machine vision detection.
The microINR® System has a multi-level On-board Quality Control. Multiple key functions and elements of the system are checked and if deviations are detected, error messages are displayed and test results are not reported.
Here's a summary of the acceptance criteria and study detailed in the provided document for the microINR System:
1. Table of Acceptance Criteria and Reported Device Performance
The FDA 510(k) summary does not explicitly list "acceptance criteria" for the self-testing use case in a table format with pass/fail thresholds. Instead, it describes clinical studies and their outcomes designed to demonstrate that the device performs equivalently for patient self-testers as for healthcare professionals, particularly in terms of accuracy and precision. The success of the study itself serves as the demonstration of meeting the required performance for the new intended use.
Here's a breakdown of the key performance metrics reported, framed against the implicit acceptance criterion of equivalence to healthcare professional (HCP) results and a laboratory reference:
| Performance Characteristic | Acceptance Criteria (Implicit) | Reported Device Performance (Patient Self-Testers vs. HCPs/Laboratory) |
|---|---|---|
| Accuracy (PST vs. HCP) | INR test results from PST should be equivalent to HCP results. | N = 225, Slope = 1.00, Intercept = 0.00, Correlation Coefficient (r) = 0.932. Shows equivalence. |
| Accuracy (PST vs. Lab) | INR test results from PST should be accurate compared to reference laboratory system. | N = 112, Slope = 0.95, Intercept = 0.12, Correlation Coefficient (r) = 0.922. Shows accuracy. |
| Precision (PST) | Demonstrate acceptable precision for self-testing. | N = 110 (paired results), Mean = 2.61, SD = 0.13, CV (%) = 5.0. |
2. Sample Size Used for the Test Set and Data Provenance
- Accuracy (PST vs. HCP): N = 225 patients. The study was conducted at "four clinical sites" and involved patients self-testing in a "home setting for up to 2 weeks" with "2 scheduled visits to their study site." This indicates a prospective study design. The country of origin of the data is not specified.
- Accuracy (PST vs. Laboratory System): N = 112 patients. Data collected at the second visit by PSTs was compared to a laboratory system. As part of the same study as above, this is also prospective, and the country of origin is not specified.
- Precision (PST): N = 110 patients (paired results). Data collected by patient self-testers at the second visit to the clinical sites. This is also prospective, and the country of origin is not specified.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
For the ground truth comparison:
- Healthcare Professionals (HCPs): The study compares patient self-tester results to "healthcare professionals using the microINR® System." While the exact number of HCPs is not stated, it implies multiple professionals across the four clinical sites. Their specific qualifications (e.g., radiologist with 10 years of experience) are not provided, beyond being "healthcare professionals."
- Laboratory System: The "ACL TOP 500" is cited as the reference laboratory system. This is an automated coagulation analyzer, implying the ground truth was established by a validated laboratory method rather than individual expert consensus.
4. Adjudication Method for the Test Set
The document does not describe an explicit adjudication method (like 2+1 or 3+1) for resolving discrepancies in the test set. Instead, it's a direct comparison of the microINR results from patient self-testers against the microINR results from healthcare professionals and against a reference laboratory system.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance
This is not applicable. The microINR System is a diagnostic medical device for measuring prothrombin time (PT) expressed as INR, not an AI-assisted diagnostic tool for interpretation by human readers. Therefore, an MRMC comparative effectiveness study where human readers improve with AI assistance is not relevant to this device.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, in a way. The device itself, the microINR System, is the "standalone algorithm" that measures INR. The studies evaluate its performance (accuracy, precision) in the hands of two different user groups (patient self-testers and healthcare professionals) and against a laboratory reference, effectively assessing its standalone performance for each user group.
7. The Type of Ground Truth Used
The ground truth used for the clinical studies was a combination of:
- Clinical Reference (HCP results): INR results obtained by trained healthcare professionals using the microINR System. This serves as a "human expert" benchmark for the device's performance when operated by trained professionals.
- Laboratory Reference Method: INR results obtained from a standard "laboratory system (ACL TOP 500)." This is an established independent gold standard for PT/INR measurement.
8. The Sample Size for the Training Set
The document does not explicitly state a "training set" sample size for the new intended use (patient self-testing). The microINR System was previously cleared, meaning its core algorithm for INR measurement was already established. The studies for this 510(k) are focused on validating its performance in the hands of self-testers, rather than "training" a new algorithm. The document mentions that "following training, the patients self-tested." This implies the patients themselves received training on how to use the device, not that their data was used to train the device's internal algorithm.
9. How the Ground Truth for the Training Set Was Established
Given that this 510(k) primarily addresses a new user population for an already cleared device, there isn't a "training set" in the sense of machine learning algorithm development. The core measurement principle and validation were established under the previous clearance (K180780), which would have involved its own validation studies against established reference methods. For the current submission, the focus is on demonstrating that trained patients can achieve equivalent results, with ground truth established as described in point 7.
§ 864.7750 Prothrombin time test.
(a)
Identification. A prothrombin time test is a device used as a general screening procedure for the detection of possible clotting factor deficiencies in the extrinsic coagulation pathway, which involves the reaction between coagulation factors III and VII, and to monitor patients receiving coumarin therapy (the administration of one of the coumarin anticoagulants in the treatment of venous thrombosis or pulmonary embolism).(b)
Classification. Class II (performance standards).