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 Performance Comparison Between Masimo W1™ and Apple Watch Series 8 (NCT05968079), a na phase not stated study. The primary outcome is Accuracy of Masimo W1™ and Apple Watch Series 8 in Determining SpO2 (Oxygen Saturation) Values in Subjects During Desaturation.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05968079 |
| Phase | Phase not stated |
| Condition | Healthy Volunteers |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 20 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Masimo Corporation |
| Results posted | Yes |
2. Clinical Question
Population
Healthy volunteers enrolled in a study with a recorded enrollment of 20. The registry description says measurements were collected during desaturation, but does not report further participant characteristics or the desaturation protocol.
Intervention
Participants in the test group received the noninvasive Masimo W1™ and Apple Watch Series 8 devices. The registry record describes both devices as being used to obtain oxygen-saturation measurements.
Comparator
Measurements from each device were compared with measurements from an FDA-cleared pulse oximetry device. The registry record does not identify that reference device by name. It also describes a performance comparison between Masimo W1™ and Apple Watch Series 8, but does not report a separate randomized control group.
Primary question
How accurately do Masimo W1™ and Apple Watch Series 8 determine SpO2 during desaturation, when their readings are compared with the FDA-cleared pulse oximetry reference? The primary outcome description specifies calculation of an arithmetic root mean square value, or ARMS, from paired measurements. Numerical ARMS findings are not reported in the registry record.
This question concerns agreement of device measurements with a reference, rather than a comparison of clinical outcomes between treatment groups. The registry record lists a timeframe of 1-6 hours for the primary outcome. It does not report numerical results for the primary endpoint, or the detailed measurement protocol needed to understand how desaturation was induced and assessed.
3. Trial Design
The registry record describes a completed, single-group device study with an enrollment of 20. Its recorded start date is 2023-09-06 and its primary completion date is 2023-10-11. The study population is listed as healthy volunteers. Each enrolled participant who took part in data collection received both Masimo W1™ and Apple Watch Series 8, according to the arm description.
The design is not described as randomized, and the registry lists allocation as NA and masking as NONE. The record therefore does not describe a blinded, randomized comparison between device groups. Its central comparisons are paired measurement comparisons: readings from the devices are evaluated against readings from an FDA-cleared pulse oximetry device. The primary outcome description also refers to paired SpO2 timing measurements from the reference sensor, Masimo W1, and Apple Watch. This pairing matters because readings are linked by measurement timing, rather than being observations from unrelated groups.
The study summary says that device performance was to be compared against FDA-cleared hospital-grade pulse oximetry technology under desaturation conditions. The identity of the reference device, participant-level procedures, and details of the desaturation conditions are not reported in the registry record. Although the record lists three outcome measures, it provides a detailed description only for the primary outcome in the information available for this analysis.
The registry marks the study as COMPLETED, but completion does not itself establish that numerical findings are available. The record lists 0 analyses. Numerical estimates for the primary outcome and details of any analysis population are not reported in the registry record. The design should therefore be read as a device-measurement study with a reference comparison, not as evidence from a randomized clinical-outcome trial.
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 | Masimo W1™ and Apple Watch Series 8 |
|---|---|
| STARTED | 20 |
| COMPLETED | 20 |
| NOT COMPLETED | 0 |
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.
Population: A total of 20 subjects were enrolled for the study
| Characteristic | Unit | Masimo W1™ and Apple Watch Series 8 |
|---|---|---|
| Participants analysed | 20 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 20 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 9 |
| Sex: Female, Male: Male | Participants | 11 |
| Race/Ethnicity, Customized: African American | Participants | 4 |
| Race/Ethnicity, Customized: Asian or Pacific Islander | Participants | 7 |
| Race/Ethnicity, Customized: Hispanic | Participants | 3 |
| Race/Ethnicity, Customized: White | Participants | 6 |
6. Primary Endpoint
The registry lists the primary outcome as Accuracy of Masimo W1™ and Apple Watch Series 8 in Determining SpO2 (Oxygen Saturation) Values in Subjects During Desaturation, measured over 1-6 hours.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Percent of oxygen saturated hemoglobin |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is accuracy of Masimo W1™ and Apple Watch Series 8 in determining SpO2, or oxygen saturation, during desaturation. The stated unit is percent of oxygen saturated hemoglobin, and the timeframe is 1-6 hours. The outcome description says accuracy is assessed by comparing each device’s SpO2 measurements with measurements from an FDA-cleared pulse oximetry device, then calculating the arithmetic root mean square value (ARMS). It also notes that the pairwise samples consist of timed measurements from the reference sensor and both devices.
In general, an agreement measure is useful when the question is whether a measurement device produces readings close to a reference. ARMS expresses the typical size of measurement error by combining the signed deviations after squaring them, averaging them, and taking a square root. Because squaring removes the direction of errors, ARMS reflects both systematic offset and scatter; it does not, by itself, show whether readings tend to be higher or lower than the reference. The outcome description says that bias and precision values are also in units of percent, but numerical bias, precision, or ARMS results are not reported in the registry record.
The reference comparison provides a basis for assessing measurement agreement under the stated study conditions. It does not establish performance in populations or settings not described in the record. The name of the reference device and additional endpoint specifications are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study question and the planned form of the primary comparison, but it does not provide numerical accuracy findings. It describes paired SpO2 measurements from Masimo W1™, Apple Watch Series 8, and an FDA-cleared pulse oximetry reference, with ARMS as the primary accuracy measure. Since the numerical ARMS, bias, and precision values are not reported in the registry record, the magnitude and direction of measurement discrepancies cannot be evaluated from the posted results.
The design has one test group: participants received both devices. This supports a within-participant, paired-measurement framing, but it is not a randomized comparison of device-assigned groups. The record lists allocation as NA and masking as NONE. Results from a paired device comparison would need to be interpreted as agreement with the reference in the studied setting, not as evidence that one device improves a clinical outcome or is superior in every population or use context.
The primary outcome description specifies an ARMS value and says that bias and precision values are presented in percent units. These measures answer related but distinct questions. Bias describes average directional deviation from the reference, while precision describes the spread of deviations. ARMS combines error magnitude without retaining its direction. As a general statistical point, a single aggregate accuracy measure can conceal patterns that matter, such as differences across the range of measured oxygen saturation or across participants. Whether such patterns were examined is not reported in the registry record.
The record lists enrollment of 20 and a primary outcome timeframe of 1-6 hours. These registry entries describe the recorded study size and measurement window, but do not establish how many paired readings contributed to each analysis. The number of usable paired observations, any exclusions, and the handling of repeated measurements are not reported in the registry record. Those details are important because a participant count alone does not describe the amount or distribution of measurement data used to estimate agreement.
The study is marked COMPLETED, while the registry lists 0 analyses and does not report numerical primary outcome results. Therefore, no conclusion about the observed accuracy of either device can be drawn from the registry information. The absence of numerical results is not evidence that the devices had similar or different performance; it leaves the size and precision of any observed differences unknown.
The sample-size material associated with the study is described as a planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such an illustration is not the trial’s own design or an observed-power calculation. In particular, the actual study is recorded as a single-group device study, and numerical illustration results are not reported in the registry record. The sponsor’s own analysis, if reported, would take precedence over any simple recalculation from summary statistics; numerical sponsor analysis results are not reported in the registry record.
9. Statistical Methods Explained
What does a paired measurement comparison mean?
In general, paired measurements are observations linked to the same unit or measurement occasion. The registry describes paired SpO2 timing measurements from the FDA-cleared reference sensor, Masimo W1, and Apple Watch. Pairing can make a comparison more informative than treating every device reading as unrelated, because readings taken at corresponding times share the same measurement context. The record does not describe the timing rules in detail, how many pairs were available, or how repeated readings within participants were handled.
A paired comparison is not the same as randomizing participants to device groups. The record describes one group in which participants received both devices, with allocation listed as NA and masking listed as NONE. Thus, the measurement comparison should be understood as an agreement assessment against a reference, not as a randomized trial of clinical effects.
What does ARMS convey?
In general, ARMS is the square root of the average squared difference between a test device reading and a reference reading. Squaring makes larger errors contribute more strongly and removes the direction of the discrepancy. The resulting measure expresses error magnitude in the same units as the underlying measurements. The registry names ARMS as the primary accuracy calculation and specifies percent units for SpO2-related bias, precision, and ARMS.
ARMS combines elements of bias and precision. Bias describes whether readings tend on average to lie on one side of the reference. Precision concerns how tightly readings cluster around their average deviation. Two devices can have similar ARMS values while having different combinations of directional offset and variability. For that reason, the separate bias and precision results can add context to an aggregate ARMS measure. Their numerical values are not reported in the registry record.
Why does the reference matter?
Accuracy in this study is defined relative to measurements from an FDA-cleared pulse oximetry device. A reference provides the comparator needed to quantify agreement; it does not make the reference error-free. General measurement science distinguishes agreement with a chosen reference from absolute truth. The registry record does not name the reference device or report its own measurement uncertainty, so those aspects cannot be assessed from the record.
The record says the comparison takes place under desaturation conditions. Measurement performance can depend on the conditions under which readings are collected. The detailed protocol, the range and progression of desaturation, and the number of measurements across conditions are not reported in the registry record. Consequently, the stated setting should not be assumed to represent conditions beyond those documented.
How should uncertainty be considered?
In general, a confidence interval describes the range of estimates compatible with the observed data under a specified statistical procedure. It helps communicate precision: a narrower interval indicates less statistical uncertainty than a wider interval, while neither interval alone establishes practical importance. The registry information described for this analysis does not report a primary-outcome estimate or confidence interval. Precision of the estimated device agreement therefore cannot be judged from the posted numerical results.
Repeated observations can create dependence: measurements from the same participant may be more alike than measurements from different participants. General statistical methods account for the structure of the data when estimating uncertainty. The registry record does not state whether readings were aggregated by participant, analyzed as individual pairs, or handled with a method that accounts for within-participant dependence. No particular procedure should be assumed.
What do planning illustrations represent?
In general, a sample-size planning calculation estimates how much information a hypothetical design might need to detect a specified effect under chosen assumptions. The record describes an illustration based on the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also says that the effect to detect is a stated fraction of the observed effect. The record’s description of the illustration does not make those assumptions part of the actual study protocol.
The actual study is described as single-group and uses paired device measurements. Equal allocation between two arms is therefore a hypothetical planning setup, not a description of this study’s enrollment or allocation. Planning estimates are not observed power, and an illustration based on an observed effect should not be mistaken for a prospective sample-size justification. The protocol’s sample-size rationale is not reported in the registry record. Numerical planning estimates are not reported in the registry record.
Any simple recalculation from posted summary statistics would be unadjusted, and the sponsor’s own analysis takes precedence if the two differ. The registry information described for this analysis does not report numerical estimates that would permit such a recalculation.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures, but detailed information for the other outcome measures is not reported in the registry record. It lists 0 analyses and does not provide a set of numerical outcome estimates for review. The record does not describe a multiplicity adjustment, a hierarchy among outcomes beyond identifying the primary outcome, or a plan for controlling false-positive findings across multiple analyses. These items are not reported in the registry record, so the handling of multiple outcomes or comparisons cannot be evaluated.
Missing-data procedures are also not reported in the registry record. In a device study with paired readings, a pair may be unavailable if one device or the reference does not produce a usable measurement at a particular time. General statistical practice requires clarity about which pairs are included and how missing readings are handled, since complete-pair analyses can differ from analyses using other strategies. The registry record does not state whether missing or unusable readings occurred, how they were classified, or whether any sensitivity analyses were performed.
The record does not identify a detailed analysis population, such as the criteria for inclusion in the primary accuracy calculation. It also does not report the number of paired measurements analyzed or how multiple readings from one participant were treated. Enrollment is recorded as 20, but enrollment alone does not disclose the analysis denominator for a measurement-level endpoint. These omissions limit assessment of selection, missingness, and the precision of the reported comparison.
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 |
|---|---|---|---|
| Masimo W1™ and Apple Watch Series 8 | 0 | 20 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Masimo W1™ and Apple Watch Series 8 | 0 of 20 |
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 |
|---|---|
| Masimo W1™ and Apple Watch Series 8 | 0 of 20 |
The adverse-event record lists the combined Masimo W1™ and Apple Watch Series 8 group, with 20 participants at risk for serious adverse events and 0 affected. It also lists 20 at risk for other adverse events and 0 affected, with 0 deaths. These are the counts recorded for this study group; they do not describe an event rate beyond the recorded participants and do not establish that no unrecorded events occurred.
Zero recorded events should be interpreted as a count in this registry record, not as proof that an event is impossible or that risk is absent. The record does not provide additional detail about event definitions, collection procedures, follow-up completeness, or whether any events were judged related to either device. Those details are not reported in the registry record. The adverse-event counts also do not substitute for the primary measurement-accuracy results, which are not reported numerically.
12. What the Result Does, and Does Not, Mean
This study addresses a specific measurement question: how Masimo W1™ and Apple Watch Series 8 SpO2 readings compare with an FDA-cleared pulse oximetry reference during desaturation in healthy volunteers. Its single-group setup and paired measurements are appropriate to describe the stated device-agreement question, as opposed to comparing randomized clinical treatment groups. The record reports enrollment of 20 and a primary outcome timeframe of 1-6 hours.
The registry record does not report numerical ARMS, bias, or precision results. It therefore does not establish the observed size of measurement error, whether one device tended to read above or below the reference, or how variable readings were. It also does not report confidence intervals or the number of paired readings analyzed. These missing results prevent an assessment of statistical precision and prevent a numerical comparison between the devices.
Even if numerical agreement estimates were available, their interpretation would be tied to the study population, measurement conditions, reference device, and analysis procedures. The registry record identifies healthy volunteers and desaturation conditions but does not provide detailed protocol information or name the reference device. Extrapolation to other populations, devices, or settings cannot be justified from the information recorded.
The record marks the study COMPLETED, but completion is distinct from reporting results. It lists 0 analyses, and numerical primary findings are not reported in the registry record. That lack of numerical results is not evidence of no difference, equivalence, or poor performance. It means the direction, size, and uncertainty of the measured agreement cannot be determined from the posted information.
The serious and other adverse-event counts are recorded as zero affected, with zero deaths, among the listed group. Those counts describe what the registry reports and should not be read as a guarantee of safety or as a substitute for complete event-collection details. The study’s statistical contribution, based on the available record, is chiefly its design and clearly stated measurement target; its empirical accuracy findings remain unavailable in the registry record.
13. Why This Trial Matters Statistically
Device comparison studies raise a statistical question different from conventional treatment trials. The central issue is often how closely measurements agree with a reference, not whether participants assigned to one arm have better clinical outcomes than participants assigned to another. This study’s record reflects that distinction: participants received both devices, and the primary outcome is based on paired SpO2 measurement comparisons with an FDA-cleared pulse oximetry device.
That design makes the structure of the observations important. Readings from the same participant and measurement time are related, so the comparison depends on how pairs are defined and how repeated readings are incorporated. The registry identifies paired timing measurements but does not report the detailed analysis procedures or the number of pairs. Recognizing those details helps readers distinguish a participant count from the amount of measurement information available.
The endpoint also illustrates why aggregate accuracy measures need context. ARMS captures the magnitude of deviations, while bias and precision help describe direction and variability. Reporting them together can make agreement easier to interpret than relying on a single measure alone. Here, the registry describes these measures but does not report numerical results, so the statistical question is clear while the empirical answer is not.
Finally, a completed registry status and a specified endpoint do not replace transparent numerical reporting. Estimates, uncertainty intervals, analysis denominators, and missing-data methods are needed to assess the strength and limitations of a device comparison. This record allows readers to identify the intended reference-based question and the broad design, while leaving those result-level assessments unresolved.
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 main limitation for interpreting this record is that numerical primary outcome results are not reported in the registry record. Without ARMS, bias, or precision estimates, the magnitude and direction of device-reference differences cannot be evaluated. No confidence interval or other uncertainty estimate is reported, so the statistical precision of any comparison is also unknown.
The study is described as a single-group comparison without masking. Participants received both devices, and the registry lists allocation as NA. This is not a randomized, blinded comparison between separate device groups. The record does not describe procedures to reduce measurement or observer bias, and no such procedures should be assumed.
The recorded enrollment is 20, but the number of paired measurements used in the endpoint analysis is not reported. The registry does not specify how repeated readings were analyzed, whether all participants contributed usable pairs, or how missing and unusable measurements were handled. These omissions make it difficult to assess the effective information available for the accuracy estimates.
The population is listed as healthy volunteers and the study summary refers to desaturation conditions. Further participant characteristics, the desaturation protocol, and the reference device’s identity are not reported in the registry record. The scope of inference is therefore limited by the sparse description of the population and testing conditions. Additional outcome details, multiplicity procedures, and the protocol’s sample-size justification are also not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Performance Comparison Between Masimo W1™ and Apple Watch Series 8 — NCT05968079.
- Registry record last updated 2025-04-09; status last verified 2025-04.
- Results first posted 2025-04-09.
- 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
NCT05968079 is a completed, single-group device study sponsored by Masimo Corporation. The record lists an enrollment of 20 healthy volunteers, a start date of 2023-09-06, and a primary completion date of 2023-10-11. Participants in the test group received Masimo W1™ and Apple Watch Series 8.
The primary outcome concerns SpO2 accuracy during desaturation over a timeframe of 1-6 hours. It is defined through paired comparisons with an FDA-cleared pulse oximetry device and calculation of ARMS; the record also refers to bias and precision. Numerical accuracy results, detailed analysis procedures, and the identity of the reference device are not reported in the registry record. The adverse-event record lists 0 serious events, 0 other events, and 0 deaths.