This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Measuring Dysphagia After ACDF Surgery Through A Novel Wearable Sensor (NCT04921800), a na na study. The primary outcome is Vibrational Frequency of Vocalization Following Surgery.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04921800 |
| Phase | NA |
| Condition | Cervical Spine Fusion |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 11 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Northwestern University |
| Results posted | Yes |
2. Clinical Question
Population
Participants undergoing anterior cervical discectomy and fusion (ACDF) for cervical spine fusion. The registry record lists an enrollment of 11 and describes post-operative monitoring in this patient population.
Intervention
Application of the ADAM mechanoacoustic skin sensor. The arm description says the sensor would be placed in the sternal notch to record anatomical data during the post-surgical period for up to 14 days.
Comparator
There is no separate control group in the registry record. This is a single-group study, and the record does not describe a like-for-like comparison between participants with and without the sensor.
Primary question
The study asks whether the wearable sensor can detect mechanoacoustic output related to motion and vocalization after surgery. The stated primary measure is vibrational frequency of vocalization in hertz during 0 to 24 hours post operative. The registry record says investigators did not collect this variable.
The broader study purpose was to assess the function and reliability of a noninvasive, skin-like electronic sensor in post-operative patients. The brief summary describes intended monitoring of heart rate, respiratory rate, swallow count, talking time, energy expenditure, neck specific motion, and body orientation. Those aims describe what the investigators sought to monitor; they do not establish that each signal was successfully recorded or evaluated.
3. Trial Design
This was a completed, single-group study sponsored by Northwestern University. The registry record lists an enrollment of 11, an allocation of NA, masking of NONE, and phase of NA. It describes ACDF as the procedure and application of the ADAM mechanoacoustic skin sensor as the device intervention. There is no randomized comparison, and the study arms should not be read as like-for-like treatment groups.
The sensor arm description says that the device would be placed at the sternal notch and used to record anatomical data during the post-surgical period for up to 14 days. The study was intended as a feasibility assessment of sensor function and reliability, rather than a comparison of clinical outcomes between different treatment strategies. The registry record does not report a separate control condition or a masking procedure.
The listed study start was 2021-03-15, and the primary completion date was 2021-12-23. The status is COMPLETED. The primary outcome was specified as vibrational frequency of vocalization following surgery, with a timeframe of 0 to 24 hours post operative. However, the registry record states that investigators did not collect this variable. It lists four outcome measures and zero analyses. Those entries do not provide outcome estimates or a statistical comparison.
The record does not report a protocol-level sample-size justification, a detailed analysis plan, or a basis for selecting the enrollment target. The sample-size assumptions associated with planning illustrations are not evidence about the original design or the precision achieved in this study.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Wearable Sensor Applied |
|---|---|
| STARTED | 11 |
| COMPLETED | 11 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Investigators did not collect this variable.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Wearable Sensor Applied |
|---|---|---|
| Participants analysed | 11 | |
| Age, Continuous | years | 57 (SD 11) |
| Sex: Female, Male: Female | Participants | 7 |
| Sex: Female, Male: Male | Participants | 4 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United States | participants | 11 |
6. Primary Endpoint
The registry lists the primary outcome as Vibrational Frequency of Vocalization Following Surgery, measured over 0 to 24 hours post operative.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The stated primary endpoint is vibrational frequency of vocalization following surgery. It is described as the sensitivity of the device to mechanoacoustic output from motion and vocalization, measured in hertz, with a timeframe of 0 to 24 hours post operative. In practical terms, the intended measure concerns whether the sensor can register vibration patterns associated with vocal activity and movement in the post-operative setting.
Such a measure can be relevant to a feasibility study because it focuses on whether a wearable device detects a physiological signal of interest. General statistical context: a device’s sensitivity to a signal is a measurement property, not by itself evidence that monitoring changes patient outcomes. Establishing that a signal can be captured and interpreted would require recorded measurements and a clear account of how those measurements are assessed.
The registry record explicitly says investigators did not collect this variable. Therefore, no frequency values, variability estimates, or evaluation of sensor sensitivity for this endpoint are reported in the registry record. The endpoint’s stated purpose should not be confused with an observed result. The brief summary names additional physiological signals that the investigators intended to monitor, but the record does not give outcome estimates for those signals either.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a feasibility study of a wearable sensor in patients after ACDF, with a single group and an enrollment of 11. Its primary outcome was intended to assess device sensitivity to mechanoacoustic output from motion and vocalization. The central interpretive limitation is that the record says this primary variable was not collected. There is consequently no posted primary-outcome estimate to interpret, and no basis in the record for describing the sensor’s performance on that endpoint.
The study’s stated aims include monitoring heart rate, respiratory rate, swallow count, talking time, energy expenditure, neck specific motion, and body orientation. These are intended signal categories, not evidence of successful capture, completeness, or measurement quality. The registry record does not provide results for them. It lists four outcome measures but zero analyses; those counts do not replace the missing measurements or provide evidence about device reliability.
There is no randomized control group or treatment comparison. As a result, this record cannot support a comparative estimate between sensor and non-sensor care, nor can it isolate an effect of the device from other influences. The study’s design is directed toward sensor feasibility and monitoring rather than a controlled clinical-effect comparison. General statistical context: without a comparison group, observed changes over time cannot by themselves establish what would have happened in the absence of the device or procedure.
The safety entries list 11 participants at risk for serious adverse events, with 0 affected, and 11 at risk for other adverse events, with 5 affected. Deaths are listed as 0. These counts are descriptive registry entries; they do not establish that the device is free of risk. The record does not give detailed event descriptions, attribution, or a safety analysis.
The information supports a cautious account of the study’s design and intended use, but not a conclusion about primary endpoint performance, signal reliability, or clinical benefit. The key distinction is between a planned measurement and a recorded result. Here, the registry identifies the planned endpoint and expressly indicates that it was not collected.
9. Statistical Methods Explained
What does a single-group design allow?
The registry record identifies the study model as single group and gives allocation as NA. That means the record does not describe randomized assignment to distinct comparison groups. The participants were monitored in the context of ACDF and application of the wearable sensor. This design can be used to examine feasibility questions, such as whether a device is used in the intended setting or whether signals are recorded. It does not, on its own, provide a randomized estimate of how outcomes differ with versus without the sensor.
General statistical context: a comparison group helps distinguish an intervention-associated difference from background variation, changes over time, or other influences. In a single-group study, those competing explanations are not separated by randomization. This matters especially when interpreting clinical changes; it does not negate the value of descriptive feasibility observations, but it limits claims that can be made from them.
What is the role of the primary endpoint?
The primary endpoint is named as vibrational frequency of vocalization following surgery. Its description focuses on device sensitivity to mechanoacoustic output from motion and vocalization, in hertz, during 0 to 24 hours post operative. Specifying an endpoint identifies the intended measurement and its timeframe. It does not mean the measurement was obtained. The registry record says investigators did not collect this variable, so no endpoint result or uncertainty estimate is available in the record.
General statistical context: a numerical estimate describes the observed data, while a confidence interval, when reported, communicates uncertainty around an estimate under the assumptions of the analysis. Neither can be interpreted when the relevant outcome values are absent. No confidence interval, p-value, or primary-outcome estimate is reported in the registry record.
What do the analysis entries tell readers?
The record lists four outcome measures and zero analyses. This indicates that outcome measures are listed but no analyses are listed in the registry record. It does not reveal why the primary variable was not collected, whether other measurements were available outside the record, or whether an analysis was conducted but not registered. Those explanations are not reported in the registry record.
General statistical context: an analysis plan ordinarily explains how outcomes are summarized, how missing observations are handled, and which population is included. Without that information, readers cannot assess prespecification, analytic choices, or whether any reported result follows a planned method. A detailed statistical analysis plan is not reported in the registry record.
How should planning illustrations be distinguished from results?
Any sample-size figures associated with planning illustrations should be understood as hypothetical planning quantities, not as measurements from this trial or as observed power. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect defined as a stated fraction of the observed effect. The record also says that time-to-event illustrations give total events, while other illustrations give participants per arm.
Those assumptions do not describe the actual single-group design, which has no two-arm randomized comparison in the registry record. They are not a record of the trial’s original sample-size justification. Such a justification is not reported in the registry record. General statistical context: sample-size planning depends on an outcome, a target effect, variability assumptions, and a design. A planning illustration can show how assumptions relate to a hypothetical design, but it cannot recover missing outcome data or establish the study’s achieved precision.
Over-dispersion is a general concern when count outcomes vary more than a model’s assumed distribution permits. If present and ignored, uncertainty can be understated. The registry record does not report a count-outcome model or an assessment of over-dispersion, so no such issue can be evaluated for this study from the record.
What cannot be inferred?
The record does not report an endpoint estimate, a variability estimate, a confidence interval, a hypothesis test, or an adjusted or unadjusted analysis for the primary outcome. It also does not report the detailed methods needed to determine how sensor readings would be processed or how reliability would be quantified. General statistical context: a measurement device may be assessed through properties such as repeatability or agreement, but those properties require an operational definition and relevant data. Neither is available for interpretation of the stated primary endpoint in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists four outcome measures, but it does not report a multiplicity strategy. It is therefore not possible to determine whether any outcomes were designated as secondary or exploratory for inferential testing, whether tests were planned, or whether an adjustment for multiple comparisons was intended. The primary outcome is named, but its variable was not collected, and zero analyses are listed.
General statistical context: when several outcomes are tested, the chance of at least one apparently unusual result can increase if each test is interpreted independently. A prespecified hierarchy, adjustment method, or clear distinction between confirmatory and exploratory analyses can help readers understand that risk. No such plan is reported in the registry record, and no outcome analyses are listed from which to assess multiplicity in practice.
Missing-data methods are also not reported. For the primary endpoint, the record does not describe a set of collected values with some missing observations; it states that investigators did not collect the variable. The reason for not collecting it, any attempts to obtain it, and any consequences for the other outcomes are not reported in the registry record. It would be inappropriate to treat the absent primary measurement as an estimated value or to assume a particular imputation method.
The analysis populations are not defined in the registry record. It does not say whether analyses were intended to include all enrolled participants, only participants with usable sensor recordings, or another population. Because no analyses are listed, there is no reported accounting of participants included in outcome analyses or of exclusions from them. These gaps limit assessment of selection, missingness, and the relationship between enrollment and analysis.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Wearable Sensor Applied | 0 | 11 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Wearable Sensor Applied | 0 of 11 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Wearable Sensor Applied | 5 of 11 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Wearable Sensor Applied |
|---|---|---|
| Pain | Musculoskeletal and connective tissue disorders | 5 of 11 |
The registry record lists 11 participants at risk for serious adverse events and 0 affected. It lists 11 participants at risk for other adverse events and 5 affected. Deaths are listed as 0, and no top serious-event terms are listed. These are descriptive counts recorded for the Wearable Sensor Applied group.
The serious-event entry means that no participants are listed as affected by a serious adverse event in this record. It does not establish that no event occurred outside the registry’s reporting scope, and it does not establish that the sensor or procedure is risk-free. The other-adverse-event entry records 5 affected participants, but the registry record does not provide event terms, severity details, attribution, or a breakdown by type.
General statistical context: safety counts are interpreted in light of how events were defined, how long participants were monitored, how events were solicited, and whether they were judged related to an intervention. Those details are not reported in the registry record. The sensor description allows recording for up to 14 days, but the record does not specify the adverse-event observation window. The counts should therefore be read as the posted registry entries, not as a complete characterization of safety.
12. What the Result Does, and Does Not, Mean
The record describes a small, single-group feasibility assessment of a noninvasive wearable sensor following ACDF. It specifies a primary measure related to vocalization frequency and describes broader intended monitoring of physiological signals. The record also states that the primary variable was not collected. Thus, the registry provides context about the study question and device use, but no primary outcome result on which to judge sensor sensitivity.
The study’s design is suited to describing a feasibility effort, but it does not provide a randomized comparison of the device against a control condition. No comparative treatment effect is reported. The record also lists zero analyses, so there are no posted inferential results to interpret. Intended monitoring should not be mistaken for confirmation that all signals were successfully captured, or that they were reliable or clinically meaningful.
General statistical context: feasibility, measurement performance, and clinical effectiveness are distinct questions. Evidence that a device can be used or can record a signal would not by itself establish that the signal improves decisions or outcomes. Conversely, the absence of the primary endpoint from this registry record is not proof that the device cannot measure the signal; it means the record does not contain the measurement needed to assess that question.
The safety entries report 0 participants affected by serious adverse events, 5 affected by other adverse events, and 0 deaths. Those figures are limited by the absence of detailed event descriptions and reporting methods. They should not be used to make a broad safety conclusion.
Overall, the registry record supports a description of the study’s intent, design, and recorded safety counts. It does not establish sensor reliability, performance on the primary endpoint, or a clinical benefit. Any stronger interpretation would require outcome data and analytic details that are not reported in the registry record.
13. Why This Trial Matters Statistically
This study raises a useful statistical distinction between collecting a signal and establishing what that signal means. A wearable device may be designed to capture physiological information continuously or noninvasively, but a feasibility question still requires usable observations and clearly defined criteria for evaluating them. The primary outcome was intended to assess sensitivity to mechanoacoustic output from motion and vocalization. Because the registry record says this variable was not collected, that measurement question remains unanswered in the posted results.
The study also illustrates why registry descriptions of intended outcomes should be separated from outcome findings. The brief summary names several signals that the sensor was intended to monitor, while the record gives no estimates for those signals. Distinguishing aims from results prevents a device’s intended capabilities from being read as demonstrated performance.
General statistical context: measurement studies benefit from explicit definitions of the signal, the conditions under which it is recorded, and the methods used to assess reliability or agreement. These choices affect how uncertainty and device performance are interpreted. The registry record does not provide such analytic details, so readers cannot evaluate those measurement properties from the posted information.
The single-group design also clarifies the boundary between feasibility and comparison. It can describe a monitoring effort in the post-operative setting, but it cannot supply a randomized estimate comparing sensor use with a control condition. That distinction is important when a study’s purpose includes both technology assessment and a broader clinical context. The record supports the former as an aim, but does not report results sufficient to assess sensor performance or clinical consequences.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary limitation is explicit: investigators did not collect the stated primary variable, vibrational frequency of vocalization following surgery. Accordingly, there is no posted result for the endpoint, despite its defined timeframe of 0 to 24 hours post operative. The registry record does not explain why it was not collected or whether a substitute measure was used.
The study is single group, with allocation listed as NA and masking listed as NONE. No control group is described, so the record does not support a controlled comparison. Enrollment was 11, and the registry lists zero analyses. The small enrollment and lack of outcome analyses leave no reported basis for estimating the precision of sensor-performance measures.
The sensor was described as being placed in the sternal notch for recording during the post-surgical period for up to 14 days. The registry record does not report whether the planned monitoring duration was achieved, how much sensor data were usable, or how recording interruptions and unusable readings were handled. It also does not describe operational methods for assessing reliability, signal quality, or agreement with another measurement.
The record names several intended physiological signals but does not provide their results. It does not report a detailed statistical analysis plan, analysis populations, missing-data methods, multiplicity procedures, or a sample-size justification for the study design. These limitations are specific to what the registry record reports and prevent assessment of the planned measurement aims beyond their description.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Measuring Dysphagia After ACDF Surgery Through A Novel Wearable Sensor — NCT04921800.
- Registry record last updated 2025-05-09; status last verified 2024-03.
- Results first posted 2024-04-10.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT04921800 is a completed, single-group feasibility assessment sponsored by Northwestern University. It enrolled 11 participants undergoing ACDF and describes application of the ADAM mechanoacoustic skin sensor at the sternal notch for post-surgical monitoring for up to 14 days. The primary outcome was vibrational frequency of vocalization following surgery, intended to assess device sensitivity to motion- and vocalization-related mechanoacoustic output during 0 to 24 hours post operative.
The registry record states that investigators did not collect the primary variable and lists zero analyses. It describes additional intended signals, including heart rate, respiratory rate, swallow count, talking time, energy expenditure, neck specific motion, and body orientation, but reports no estimates for them. Safety entries list 0 participants affected by serious adverse events, 5 affected by other adverse events, and 0 deaths. The record does not describe a randomized control group or provide results that establish sensor performance.