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The NightWatch+ US is a prescription only device that is indicated for use as an adjunct to seizure monitoring of children age 4 till 16 diagnosed with epilepsy having Nocturnal Epileptic Major Motor Seizures which includes tonic-clonic (TC), tonic (if clustered or prolonged >30 seconds), hyperkinetic and TC-like seizures, in home or residential facilities during periods of rest. The Sensor of the device is worn on the upper arm and measures heart rate and motion data to detect patterns that may be associated with nocturnal epileptic motor seizures in patients with epilepsy. When a seizure event is detected by the Sensor of the NightWatch+ US, it sends a command to the paired wireless alarm station of the NightWatch+ US that is programmed to initiate an alarm to a designated caregiver. The system records and stores data from seizure events. The data can be viewed by the user in a cloud based data portal. The NightWatch+ US is not intended to diagnose specific seizure types.

NightWatch+ US consists of a sensor worn during sleep on the biceps of the upper arm and an alarm station. The sensor consists of a heart rate sensor using PPG (photoplethysmography), a ACC (Accelerometry) movement sensor, and a microprocessor. The microprocessor processes the data from the sensors using a detection algorithm which detects if the sensor readings match pre-programmed parameters that are associated with nocturnal epileptic major motor seizures. When a nocturnal epileptic major motor seizures is detected, the seizure alarm is triggered and transferred from the sensor to the accompanying alarm station which alarms the caregiver by a sound and a blinking LED light. The seizure alarms data can be transferred from the alarm station, using an ethernet connection, to a database in the cloud to be viewed a web-based interface called NightWatch Portal to be able to monitor seizure frequency overtime.

The provided text describes the acceptance criteria and a study proving the device meets these criteria. However, it explicitly states that "performance goals or acceptance criteria for other endpoints were not defined" beyond an 80% sensitivity estimate for the study itself. This means that while the study evaluated performance metrics like sensitivity and false alarm rates, these were reported as results of the study, not as pre-defined acceptance criteria the device needed to meet for regulatory clearance. The document focuses on demonstrating substantial equivalence to a predicate device, arguing that the reported performance is comparable.

Therefore, the table of "Acceptance Criteria" will reflect the reported performance values from the study, as these are the figures the FDA appears to have accepted for clearance based on the substantial equivalence argument, rather than explicitly stated pre-market acceptance thresholds.

Acceptance Criteria and Device Performance

Study Details

1. Sample Size and Data Provenance:

   • Test Set Sample Size: 53 children aged 4-16 years.
   • Data Provenance: The study by van Westrhenen et al. 2023 was a "phase 4, multicenter, prospective, video-controlled, in-home study." The specific country of origin is not explicitly stated, but the company (LivAssured BV) is based in the Netherlands, and the lead author's affiliation (van Westrhenen) is often associated with Dutch institutions, suggesting data primarily from Europe.

2. Number of Experts and Qualifications for Ground Truth:

   • Number of Experts: Two principal investigators (R.D.T. and R.H.C.L.) consulted for final decisions in case of discrepancies or doubt in video annotations. Their specific qualifications (e.g., years of experience, direct specialty) are not detailed beyond being "principal investigators" in a study focused on epilepsy, implying clinical expertise in neurology/epileptology.
   • Other Reviewers: "Trained trial nurses" annotated events and retrospectively analyzed video tracings.

3. Adjudication Method for the Test Set:

   • The primary method involved "Trained trial nurses" annotating all events (NightWatch alarms, video alarms, and caregivers' seizure diary) while blinded to alarm type and sensor data.
   • Adjudication Process: In cases of discrepancies between nurses' annotations or doubt, the trial nurses consulted one of the two principal investigators for a final decision.
   • Quality Control: The principal investigators double-checked a random sample of 5% of the annotations. Additionally, trained trial nurses fully screened the video of 5% of all nights for missed seizures.

4. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:

   • No, a formal MRMC comparative effectiveness study was explicitly mentioned or described wherein human readers' performance with AI assistance was compared to their performance without AI assistance. The study focuses on evaluating the device's standalone performance and demonstrating its functionality as an adjunct to seizure monitoring.

5. Standalone Performance:

   • Yes, the study primarily assessed the standalone performance of the NightWatch+ US algorithm in detecting nocturnal epileptic major motor seizures. The reported sensitivity and false alarm rates reflect the algorithm's performance in detecting events based on physiological signals (heart rate and motion data) and alerting caregivers.

6. Type of Ground Truth Used:

   • Video Monitoring / Expert Consensus: The ground truth was established through extensive video monitoring of patients. Trained trial nurses annotated events from these video recordings. In cases of disagreement or doubt, principal investigators provided a final decision, effectively establishing an expert consensus based on video evidence. The document states, "Video is an equally robust reference standard to Video-EEG provided the whole dataset is reviewed for inferring the reference standard as recognized by the International League Against Epilepsy (ILAE)."
   • Caregiver Diaries: Caregivers' seizure diaries were also part of the input scrutinized alongside video, but video was the definitive reference.

7. Sample Size for Training Set:

   • The provided 510(k) summary does not specify the sample size or characteristics of the training set used for the NightWatch+ US algorithm. It states that the "seizure detection method, algorithms and components used for seizure detection are identical" to the predecessor NightWatch and NightWatch+, implying development and training occurred prior to this specific clearance study, but details about that initial training data are not found in this document.

8. How Ground Truth for Training Set Was Established:

   • As the training set details are not provided in this regulatory document, the method for establishing ground truth for any potential training data is also not described. It's implied that similar clinical data (possibly from the predecessor device's accumulated experience and studies) would have been used for algorithm development and refinement, which typically involves expert review of clinical events.

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