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 Post-Approval Study of the NexStent Carotid Stent System and the FilterWire EZ Embolic Protection System: SONOMA (NCT00478673), a na phase 4 study. The primary outcome is Number of Participants Who Experienced a 30-Day Major Adverse Event (MAE).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00478673 |
| Phase | Phase 4 |
| Condition | Carotid Stenosis |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 298 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boston Scientific Corporation |
| Results posted | Yes |
2. Clinical Question
Population
The registry concerns people with carotid stenosis who were enrolled in a post-approval evaluation. Enrollment was 298. The primary outcome population is described as enrolled subjects who experienced a 30-day major adverse event and/or completed a follow-up evaluation at least 23 days after the procedure. The record does not give a separate evaluable-population count.
Intervention
The devices named in the evaluation are the NexStent Carotid Stent System, with a Monorail Delivery System, and the FilterWire EZ Embolic Protection System. The study objective was to confirm safety in routine clinical practice and identify rare or unanticipated device-related events.
Comparator
The registry describes a single-group study and does not report a comparator group. It is not a randomized comparison. The safety figures for the NexStent group therefore should not be read as a comparison against an untreated group or another device group.
Primary question
The primary endpoint counts participants with a major adverse event within 30 days after the procedure. The record defines these events as death, stroke, or myocardial infarction during days 0–30. Its stated aim is safety evaluation, not a comparison of treatment effects. The numerical primary-endpoint result is not reported in the registry record.
3. Trial Design
SONOMA is identified as a Phase 4, single-group, post-approval study of the NexStent Carotid Stent System in conjunction with the FilterWire EZ Embolic Protection System. The registry lists Boston Scientific Corporation as the sponsor. Enrollment was 298, and the condition listed is carotid stenosis. The study began in 2007-05, its primary completion date is 2009-07, and its status is terminated.
Allocation is recorded as not applicable, and masking is listed as none. This is not a randomized comparison, and the record does not describe a parallel control arm. The single-group design can describe observed events in the enrolled cohort, but by itself it does not estimate how outcomes would have differed under another device or treatment. The registry does not report a reason for termination, so the status alone does not establish why the study ended.
The stated objective was to confirm safety in routine clinical practice and identify rare or unanticipated device-related events. The two listed interventions are devices: the NexStent Carotid Stent System with Monorail Delivery System and the FilterWire EZ Embolic Protection System. The primary endpoint is a participant count for major adverse events through 30 days. The registry record lists two outcome measures but no analyses. It does not report a detailed protocol, a sample-size justification, or a statistical analysis plan.
Because the evaluation has no randomized control group, observed event counts should be interpreted descriptively. They can show what was recorded in this cohort, but cannot separate device-related events from events attributable to the underlying condition, the procedure, or other factors. The record’s stated safety objective is consistent with describing event occurrence, but it does not establish causal attribution for individual events.
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.
30-Days Post-Procedure
| Stage | NexStent Carotid Stent System |
|---|---|
| STARTED | 298 |
| COMPLETED | 288 |
| NOT COMPLETED | 10 |
Reasons for not completing this period:
| Reason | NexStent Carotid Stent System |
|---|---|
| Death | 2 |
| Withdrawal by Subject | 1 |
| Missed Visit | 7 |
12-Months Post-Procedure
| Stage | NexStent Carotid Stent System |
|---|---|
| STARTED | 295 |
| COMPLETED | 231 |
| NOT COMPLETED | 64 |
Reasons for not completing this period:
| Reason | NexStent Carotid Stent System |
|---|---|
| Death | 23 |
| Lost to Follow-up | 4 |
| Withdrawal by Subject | 6 |
| Missed Visit | 25 |
| Visit Not Required by Protocol | 6 |
Analysis population for the primary outcome, as defined in the registry: ITT Analysis: All enrolled subjects who experienced a 30-day MAE and/or completed a follow-up evaluation \>=23 days post-procedure were evaluable. Subjects who experienced more than one MAE within 30 days were counted in the number of subjects with each applicable event, but were only counted once in the number of subjects with overall 30-day MAE.
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 | NexStent Carotid Stent System |
|---|---|---|
| Participants analysed | 298 | |
| Age Continuous | Years | 72.2 (SD 9.6) |
| Sex: Female, Male: Female | Participants | 119 |
| Sex: Female, Male: Male | Participants | 179 |
| Race/Ethnicity, Customized: Hispanic or Latino | Participants | 15 |
| Race/Ethnicity, Customized: Caucasian | Participants | 258 |
| Race/Ethnicity, Customized: Asian | Participants | 2 |
| Race/Ethnicity, Customized: Black, of African Heritage | Participants | 20 |
| Race/Ethnicity, Customized: Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race/Ethnicity, Customized: American Indian or Alaska Native | Participants | 1 |
| Race/Ethnicity, Customized: Other | Participants | 2 |
| Region of Enrollment: United States | Participants | 298 |
| Current Carotid Bruit: Current Carotid Bruit | Participants | 175 |
| Current Carotid Bruit: No Current Carotid Bruit | Participants | 82 |
| Current Carotid Bruit: Unknown | Participants | 41 |
| History of Carotid Atherosclerosis: History of Carotid Atherosclerosis | Participants | 187 |
| History of Carotid Atherosclerosis: No History of Carotid Atherosclerosis | Participants | 101 |
| History of Carotid Atherosclerosis: Unknown | Participants | 10 |
| History of Transient Ischemic Attack (TIA): History of TIA | Participants | 77 |
| History of Transient Ischemic Attack (TIA): No History of TIA | Participants | 207 |
| History of Transient Ischemic Attack (TIA): Unknown | Participants | 14 |
| History of Cerebrovascular Accident (CVA): History of CVA | Participants | 62 |
| History of Cerebrovascular Accident (CVA): No History of CVA | Participants | 233 |
| History of Cerebrovascular Accident (CVA): Unknown | Participants | 3 |
| History of Vertebrobasilar Occlusive Disease: History of Vertebrobasilar Occlusive Disease | Participants | 11 |
| History of Vertebrobasilar Occlusive Disease: No History of Vertebrobasilar Occlusive Disease | Participants | 267 |
| History of Vertebrobasilar Occlusive Disease: Unknown | Participants | 20 |
| History of Seizure: History of Seizure | Participants | 5 |
| History of Seizure: No History of Seizure | Participants | 290 |
| History of Seizure: Unknown | Participants | 3 |
| History of Carotid Endarterectomy (CEA): History of CEA | Participants | 74 |
| History of Carotid Endarterectomy (CEA): No History of CEA | Participants | 223 |
| History of Carotid Endarterectomy (CEA): Unknown | Participants | 1 |
| History of Percutaneous Transluminal Angioplasty (PTA): History of PTA | Participants | 15 |
| History of Percutaneous Transluminal Angioplasty (PTA): No History of PTA | Participants | 282 |
| History of Percutaneous Transluminal Angioplasty (PTA): Unknown | Participants | 1 |
| History of Carotid Restenosis: History of Carotid Restenosis | Participants | 49 |
| History of Carotid Restenosis: No History of Carotid Restenosis | Participants | 246 |
| History of Carotid Restenosis: Unknown | Participants | 3 |
| History of Upper Extremity Fibromuscular Dysplasia (FMD): History of Upper Extremity FMD | Participants | 1 |
| History of Upper Extremity Fibromuscular Dysplasia (FMD): No History of Upper Extremity FMD | Participants | 292 |
| History of Upper Extremity Fibromuscular Dysplasia (FMD): Unknown | Participants | 5 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Who Experienced a 30-Day Major Adverse Event (MAE), measured over 30 Days.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants who experienced a 30-day major adverse event. The registry defines a major adverse event as any death, stroke, or myocardial infarction occurring from 0–30 days after the procedure. This is a composite safety outcome: it combines several clinically important event types into a single endpoint, while the registry’s definition retains those component event categories.
A participant count is useful for expressing how many people in the evaluated group met the endpoint definition. It is different from an event count: if a participant has more than one type of event, the record says that person is included for each applicable event category. The description also says participants with more than one major adverse event within 30 days were counted in the number of subjects with each applicable event, while counted only once in a truncated final clause. Since that clause is incomplete in the registry record, its full counting instruction is not reported.
The endpoint is used to assess safety during a defined period after a procedure. Combining death, stroke, and myocardial infarction gives a broad summary, but the combined count does not show the frequency or clinical circumstances of each component unless those are reported separately. The numerical primary-endpoint result is not reported in the registry record, so the endpoint definition can be described but its observed result cannot be interpreted.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary outcome and its timeframe, but does not report a numerical result for the number of participants with a 30-day major adverse event. Consequently, the primary endpoint cannot be quantified from the information recorded. There is no basis in the registry record for describing the observed primary-event frequency, its precision, or how the event categories contributed to the composite outcome.
The safety objective was to evaluate the devices in routine clinical practice and identify rare or unanticipated device-related events. The record does list adverse-event figures for the NexStent group: 298 at risk, 150 with serious adverse events, and 72 with other adverse events. These are descriptive figures for the reported group, not a comparison between treatment arms. No causal conclusion about the devices follows from these counts alone. The adverse-event listings also do not substitute for the missing numerical result for the prespecified primary endpoint.
The record gives serious-event terms with percentages, including hypotension at 6.7%, carotid artery stenosis at 5.4%, anaemia at 4.7%, cardiac failure congestive at 4.0%, non-cardiac chest pain at 4.0%, and chronic obstructive pulmonary disease at 3.4%. These are listed terms, not a complete account of all events or their clinical context. The record does not specify in this listing whether each percentage refers to participants, episodes, or another denominator. The percentages should therefore be read as registry-reported values rather than independently reconstructed rates.
The study is single-group, with allocation recorded as not applicable and masking recorded as none. These design features matter because observed events cannot be contrasted with a concurrently randomized control group, and the registry does not support a treatment-effect estimate. A comparison with an external or historical benchmark is also not reported. The findings can describe the enrolled cohort as recorded, but cannot establish what would have occurred under an alternative approach.
The sample-size material is described as a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It is not the study’s own design justification. The stated information does not give the resulting planning values or the underlying observed effect, so those quantities cannot be interpreted from the registry record. Such planning illustrations would not be observed power and would not repair the absence of a reported primary outcome value.
9. Statistical Methods Explained
The registry characterizes the primary outcome as a binary participant outcome reported as a number: whether a participant experienced a major adverse event within the defined period. The event definition includes death, stroke, or myocardial infarction from 0–30 days after the procedure. In a binary endpoint, each participant is classified according to whether the endpoint occurred under the stated rule. The published count is meaningful only alongside a clearly defined analysis population and denominator.
What does a participant count represent?
A count of participants is not necessarily the same as a count of events. If a participant experiences more than one component event, a composite endpoint may count that participant once for the overall endpoint while separately recording component events. The registry’s population description says subjects with more than one major adverse event were counted in the number of subjects with each applicable event, but its final counting clause is truncated. The complete rule for combining or deduplicating component events is therefore not reported in the registry record.
The primary outcome population is labelled ITT Analysis. The description says enrolled subjects who experienced a 30-day major adverse event and/or completed a follow-up evaluation at least 23 days after the procedure were evaluable. This wording does not provide the number evaluable, explain how early withdrawals or unavailable follow-up were handled, or state whether every enrolled subject contributed to the endpoint denominator. A numerical endpoint count without a corresponding, clearly defined denominator would not establish an event rate.
Why does study design affect interpretation?
A single-group study describes outcomes observed among participants exposed to the study devices. It does not provide a randomized comparison against another device or a control intervention. Random allocation, when used, helps balance measured and unmeasured baseline differences across groups. Since allocation is listed as not applicable and the study model is single group, there is no randomized control comparison from which to estimate a relative treatment effect. The study can still record safety events, but causal attribution requires information beyond a group-level count.
Masking is listed as none. In general, masking can limit the influence of knowledge about treatment on assessment or reporting, depending on who is masked and how outcomes are evaluated. The registry does not describe masked assessment procedures. The record also does not report a detailed protocol or statistical analysis plan, so the endpoint adjudication process and prespecified analysis choices cannot be assessed from this information.
What can uncertainty measures add?
In general, a confidence interval expresses the range of values reasonably compatible with data under a specified statistical model and sampling assumptions. For an event proportion, it communicates precision in addition to the observed estimate. A narrow interval generally indicates greater precision than a wide interval, while neither interval width nor the point estimate alone establishes causality. The registry record does not report a confidence interval for the primary outcome, and it does not report the numerical primary endpoint result needed to interpret one.
For binary outcomes, a simple binomial model is a common general framework when participants contribute independent outcome classifications and the event definition and observation period are consistent. The registry record does not state a model for the primary endpoint. It would therefore be inappropriate to attribute a particular method, adjustment, or variance assumption to the sponsor. If observations were clustered or event counts showed over-dispersion relative to a chosen model, general methods would need to account for that extra variability; the record does not report such an analysis or whether these issues arose.
How should the planning illustration be read?
The registry’s planning description specifies a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and target effects expressed as fractions of an observed effect. It explicitly characterizes the sample-size work as a planning illustration computed from the observed effect, rather than the trial’s own design. The stated results do not include the observed effect or numerical planning values. No number of participants per arm for 80% power or for any other target should be inferred from the assumptions alone.
In general, a planning calculation asks how much information a proposed future comparison might require under specified assumptions. It does not establish the probability that the completed study found a true effect, and it is not observed power. The description distinguishes total events for time-to-event calculations from participants per arm for other calculations. The endpoint discussed in SONOMA is a participant-count safety outcome, and the planning description is not evidence that SONOMA itself used a two-arm design.
The record lists no analyses. It does not report hypothesis tests, confidence intervals, adjusted estimates, interim analyses, or a multiplicity procedure. General explanations of those methods cannot be treated as descriptions of what was done in SONOMA. The sponsor’s analysis, if any, and its interpretation are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists two outcome measures and identifies the 30-day major adverse event count as the primary outcome. It lists no analyses. A statistical analysis plan, including any hypothesis-testing strategy or multiplicity adjustment, is not reported in the registry record. It is therefore not possible to determine whether multiple outcomes were tested, whether a hierarchy was prespecified, or how any family of comparisons was handled.
Missing-data handling is also not described in sufficient detail to assess its effect on the primary endpoint. The population description says enrolled subjects who experienced a major adverse event and/or completed follow-up at least 23 days after the procedure were evaluable. It does not report the evaluable count, the completeness of follow-up, the treatment of participants without sufficient follow-up, or any imputation or sensitivity analysis. These details matter because incomplete outcome ascertainment can affect both the numerator and denominator used to describe an event rate.
The primary endpoint result itself is not reported in the registry record, so the effect of missing data on that result cannot be assessed. Nor does the record describe whether an independent committee reviewed or adjudicated events. These omissions do not prove that procedures were absent; they mean their use is not reported in the registry record.
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 |
|---|---|---|---|
| NexStent Carotid Stent System | 150 | 298 | 50.3% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5.0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| NexStent Carotid Stent System | 72 of 298 |
Most frequent serious adverse event terms
| Event term | Organ system | NexStent Carotid Stent System |
|---|---|---|
| Hypotension | Vascular disorders | 20 of 298 |
| Carotid artery stenosis | Nervous system disorders | 16 of 298 |
| Anaemia | Blood and lymphatic system disorders | 14 of 298 |
| Cardiac failure congestive | Cardiac disorders | 12 of 298 |
| Non-cardiac chest pain | General disorders | 12 of 298 |
| Chronic obstructive pulmonary disease | Respiratory, thoracic and mediastinal disorders | 10 of 298 |
| Myocardial infarction | Cardiac disorders | 8 of 298 |
| Pneumonia | Infections and infestations | 8 of 298 |
| Transient ischaemic attack | Nervous system disorders | 8 of 298 |
| Angina pectoris | Cardiac disorders | 7 of 298 |
Most frequent non-serious adverse event terms
| Event term | Organ system | NexStent Carotid Stent System |
|---|---|---|
| Carotid artery stenosis | Nervous system disorders | 53 of 298 |
| Hypotension | Vascular disorders | 24 of 298 |
Serious events with the highest arm-level rate: hypotension (6.7%), carotid artery stenosis (5.4%), anaemia (4.7%), cardiac failure congestive (4.0%), non-cardiac chest pain (4.0%).
The NexStent group’s adverse-event listing reports 298 at risk, 150 with serious adverse events, and 72 with other adverse events. These are registry-recorded figures for the study group, not comparative treatment effects. The serious-event terms listed include hypotension (6.7%), carotid artery stenosis (5.4%), anaemia (4.7%), cardiac failure congestive (4.0%), non-cardiac chest pain (4.0%), and chronic obstructive pulmonary disease (3.4%).
The term percentages should be read as they appear in the registry record. The listing does not specify whether they describe participants with each term or event episodes, and it does not give further detail about severity, timing, relatedness, recurrence, or clinical adjudication. It also does not establish that a listed event was caused by either device. Serious adverse events and the primary 30-day composite endpoint are not interchangeable: the primary definition is limited to death, stroke, or myocardial infarction during 0–30 days after the procedure. The numerical result for that endpoint is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The record establishes that SONOMA was a post-approval, single-group evaluation intended to assess safety in routine clinical practice and identify rare or unanticipated device-related events. It also provides a definition and timeframe for its primary safety endpoint. The primary endpoint is not a broad count of every adverse event: it is limited to death, stroke, or myocardial infarction within 30 days after the procedure.
The record does not report the numerical primary-endpoint result. Therefore, it cannot establish from the posted information how many participants experienced the defined outcome, what proportion of the evaluable group that count represents, or how precisely the event frequency was estimated. The listed serious and other adverse-event figures provide additional descriptive safety information, but they do not supply the missing primary result or answer the same clinical question.
The design also limits what can be concluded. With a single group and no randomized comparator, the record cannot estimate the difference in outcomes versus another device or treatment. Observed events in a post-approval cohort may be relevant to describing experience in that cohort, but a group-level record cannot by itself determine whether a particular event was caused by the device or procedure. No causal conclusion or comparative treatment benefit should be inferred.
The registry status is terminated, but a reason for termination is not reported in the registry record. The record does not report the sponsor’s full statistical analysis, endpoint confidence intervals, a detailed missing-data approach, or a sample-size justification. Those omissions leave uncertainty about analysis choices and outcome precision. They should be distinguished from evidence that an analysis or procedure was not performed; the registry record simply does not report it.
13. Why This Trial Matters Statistically
Post-approval safety studies address questions that may not be answered by a tightly controlled trial alone. SONOMA’s stated aim was to evaluate the NexStent Carotid Stent System and FilterWire EZ Embolic Protection System in routine clinical practice and to identify rare or unanticipated device-related events. The registry’s focus on safety, together with its 30-day composite endpoint, makes clear why event definitions and follow-up completeness are central to interpretation.
The record also illustrates the distinction between a study objective and a reported result. A detailed definition of death, stroke, and myocardial infarction does not itself show how often those outcomes occurred. The numerical primary-endpoint result is not reported in the registry record, and there is no accompanying interval estimate to communicate precision. Transparent outcome counts, evaluable denominators, and follow-up information are necessary for readers to assess what the data support.
Its single-group design is important statistically. A cohort can document observed safety events, but without a randomized comparison it cannot establish how those events differ from outcomes under another approach. This distinction is especially important when a study’s purpose includes identifying events that might be related to a device: event observation is not equivalent to proof of causation.
Finally, the registry’s planning description should be separated from the completed study’s design. Its assumptions describe an illustrative calculation for a two-arm comparison, while SONOMA is recorded as single group. Planning calculations can support future study design, but do not substitute for observed outcomes, and are not evidence of observed power. The record demonstrates why statistical interpretation depends on the match between design, outcome reporting, and the question being asked.
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 for interpretation is that the registry record does not report a numerical result for the primary endpoint. Although the endpoint definition, timeframe, and analysis-population wording are available, the count of participants meeting the definition and the corresponding denominator are not. The registry therefore does not support an estimate of the primary event frequency or its precision.
The single-group design provides no randomized control comparison. Consequently, event counts cannot establish relative safety versus another device or treatment, and they cannot isolate device effects from the procedure, underlying carotid stenosis, or other influences. Masking is listed as none; further information about outcome assessment or event adjudication is not reported.
The primary population description is incomplete at its end and does not state the evaluable count or full handling of participants with incomplete follow-up. The record does not report a missing-data analysis, sensitivity analysis, confidence interval, hypothesis test, multiplicity approach, interim analysis, or detailed statistical plan. It also does not provide the reason for the terminated status. The adverse-event term listing gives percentages but does not specify their denominator or clarify whether they refer to participants or event episodes.
Finally, the planning calculation is explicitly an illustration, not the study’s own design justification. Its numeric results and the observed effect on which it is based are not reported in the registry record for interpretation. These limitations define what can be concluded from the registry record; they do not establish that unreported procedures were not undertaken.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Post-Approval Study of the NexStent Carotid Stent System and the FilterWire EZ Embolic Protection System: SONOMA — NCT00478673.
- Registry record last updated 2012-08-07; status last verified 2012-07.
- Results first posted 2012-08-07.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
SONOMA (NCT00478673) is a Phase 4, post-approval, single-group study sponsored by Boston Scientific Corporation. It evaluated the NexStent Carotid Stent System with the FilterWire EZ Embolic Protection System in people with carotid stenosis. Enrollment was 298. The registry lists the study as terminated, with start in 2007-05 and primary completion in 2009-07.
The primary outcome is the number of participants with death, stroke, or myocardial infarction within 30 days after the procedure. The record states a safety objective focused on routine clinical practice and identifying rare or unanticipated device-related events. However, the numerical primary-endpoint result, its denominator, and its precision are not reported in the registry record. The study has no randomized comparator, and the available adverse-event figures are descriptive rather than comparative.