Safety and Effectiveness of the Ultrasonic Propulsion of Kidney Stones: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Effectiveness of the Ultrasonic Propulsion of Kidney Stones (NCT02028559), a non-randomized na study. The primary outcome is Measurement of Stone Motion Caused by Ultrasound.

2. Clinical Question

The study’s stated aims vary by participant group. In some groups, the intended purpose is to move fragments within the kidney to facilitate passage; in obstructing-stone groups, the stated aim includes moving a symptomatic stone to relieve symptoms and facilitate passage. These are study aims, not findings. The primary endpoint is narrower: it concerns whether motion was observed, not whether participants experienced fewer symptoms, avoided retreatment, or passed a stone. Results for those clinical outcomes are not reported in the registry record.

3. Trial Design

The registry identifies this as a nonrandomized, single-group study with single masking and phase listed as not applicable. The listed enrollment is 172. The sponsor is the University of Washington. The study status is active, not recruiting; the registry lists a start date of 2013-12-17 and a primary completion date of 2025-08-01. These record details describe the study’s registration and status, not the number of participants included in any particular endpoint analysis.

The study is organized into multiple population groups rather than one uniform clinical setting. The descriptions include an initial feasibility group, participants with small stones under observation, people receiving ultrasonic propulsion concurrently with ureteroscopy and laser lithotripsy, participants with obstructing stones, and participants with residual fragments after lithotripsy. The obstructing-stone descriptions distinguish pushing only from dislodging plus pushing. The interventions list Propulse 1 with a C5-2 probe and Propulse 1 with an SC-X probe.

The residual-fragment descriptions name treatment and control groups, and one description calls this a randomized control trial. However, the overall design fields classify the study as nonrandomized and single-group, and the registry explicitly cautions that the arms are not a like-for-like control comparison. The record does not explain how participants were allocated across all groups, or clarify the relationship between the residual-fragment labels and the overall design classification. Therefore, those group labels should not be read as establishing a randomized comparison for the whole study.

The masking field says single, but who was masked and how masking was implemented are not reported in the registry record. Further protocol details, including the rationale for the listed enrollment and any planned interim analyses, are not reported in the registry record.

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.

Before assignment: 172 subjects are considered enrolled in this study for one of the groups defined below. 249 subjects were consented for the study. 77 subjects screen failed after consent but before undergoing any ultrasonic propulsion procedure. Since these subjects did not qualify for the study and were not assigned to an arm/group, they are not considered enrolled or included in the data provided below. The start of the study is defined as receiving at least one ultrasonic propulsion therapy pulse.

Only the first 6 of 7 groups are shown.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All subjects who were exposed to at least one ultrasonic propulsion burst.

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.

Only the first 6 of 8 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Measurement of Stone Motion Caused by Ultrasound, measured over At the time of the procedure. To be evaluated with each therapy pulse over an approximately 1-hour study. Confirmed with post-procedure review of the study video..

The primary endpoint is titled “Measurement of Stone Motion Caused by Ultrasound.” It is defined as the percentage of study participants for whom stone motion was observed on real-time ultrasound images. Its stated population is all subjects exposed to at least one ultrasonic propulsion burst. The timing is during the procedure, with evaluation after each therapy pulse over an approximately 1-hour study and confirmation by reviewing the procedure video afterward.

This endpoint captures an observable response to the device: whether stone motion was seen. It is therefore a measure of movement, not a direct measure of stone passage, pain relief, avoidance of retreatment, or prevention of later symptomatic events. Those outcomes are mentioned as possible goals in the study summary, but their results are not reported in the registry record.

General statistical context: A percentage endpoint expresses the number of participants meeting a defined condition relative to a specified participant group. For it to be interpreted, readers need both the result and the denominator used in the analysis, along with information about how observations were classified and how missing assessments were handled. The registry describes the intended endpoint and population, but does not report the observed percentage, the number assessed, or a confidence interval. Consequently, the precision of the primary endpoint estimate cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical context: The primary endpoint is binary at the participant level: each exposed participant either had stone motion observed or did not, according to the endpoint definition. A group percentage would summarize the share meeting the endpoint. Interpreting that percentage requires knowing how many participants were assessed and how many met the definition. Neither the observed result nor its analysis denominator is reported in the registry record.

What does the confidence interval describe?

General statistical context: A confidence interval gives a range of values compatible with an estimate under the method used to construct it. For a participant percentage, it can convey how much uncertainty remains because the estimate is based on a finite set of observations. A narrow interval indicates greater precision than a wide interval, but an interval does not by itself establish clinical importance or eliminate concerns about study design. No confidence interval for the primary endpoint is reported in the registry record.

What would a comparison require?

General statistical context: A comparative estimate asks how an outcome differs between groups. Its interpretation depends on how participants entered those groups, whether the groups are comparable, which outcome and time point were selected, and how the analysis addressed differences in baseline characteristics or follow-up. In randomized studies, random allocation can support a causal comparison when appropriately implemented and analyzed. In nonrandomized settings, group differences may also reflect why participants received one approach rather than another. Here, the registry classifies the overall study as nonrandomized and explicitly warns that the arms are not a like-for-like control comparison. No comparative analysis is reported.

Why does the outcome definition matter?

General statistical context: A measure should be interpreted according to the event it actually records. Observed stone motion on an ultrasound image is not equivalent to successful passage, symptom improvement, or avoidance of additional treatment. Those may be relevant clinical outcomes, but they are distinct from the stated primary endpoint. The record’s summary describes potential goals for different groups; it does not report results for those goals. Video review is named as a way to confirm motion observations, but details of adjudication, disagreement resolution, or quality control are not reported in the registry record.

How should the planning assumptions be read?

The registry describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is specified as a fraction of the observed effect. These are assumptions for planning illustrations, not reported characteristics of the study’s original design. The record does not report the observed effect or the resulting planning values.

General statistical context: Sample-size planning estimates the number of observations needed under chosen assumptions about effect size, variability, significance level, and desired power. Changing those assumptions can change the planned sample size. A calculation based on an observed effect is retrospective and can be unstable, especially when that effect is uncertain. Such a calculation should not be described as observed power, and it does not show that an enrolled study was adequately powered. Planning counts are not clinical outcomes and do not replace estimates with uncertainty intervals.

What can be inferred from the posted analyses?

The registry lists four outcome measures and zero analyses. No inferential method, effect estimate, confidence interval, or hypothesis-test result is posted for the primary endpoint. The statistical analysis plan, including any adjustments, subgroup analyses, or interim analyses, is not reported in the registry record. The absence of a posted analysis means the primary endpoint cannot be statistically interpreted from the registry information; it does not establish that no analysis was conducted outside the registry.

General statistical context: Over-dispersion matters when variation in observed outcomes is greater than a chosen model expects. A model that underestimates variation can produce confidence intervals that are too narrow and tests that are too optimistic. Whether over-dispersion is relevant depends on the outcome structure and statistical model. The registry record does not report a model for the primary endpoint, so no claim about over-dispersion or a particular adjustment can be made for this study.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("First in Human (FIH)", "De Novo Small Stone", "Concurrent With URS", "Obstructing Stone - Pushing Only", "Obstructing Stone - Dislodging + Pushing", "Residual Fragment (Treatment Group)")
n      <- c(15, 2, 18, 16, 13, 54)
events <- c(14, 1, 15, 11, 8, 41)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  First in Human (FIH)  15  14  93.3  68.1  99.8  70.2  98.8  69.8  98.4
ARM  De Novo Small Stone  2  1  50.0  1.3  98.7  9.5  90.5  9.4  90.6
ARM  Concurrent With URS  18  15  83.3  58.6  96.4  60.8  94.2  60.4  93.9
ARM  Obstructing Stone - Pushing Only  16  11  68.8  41.3  89.0  44.4  85.8  44.0  85.8
ARM  Obstructing Stone - Dislodging + Pushing  13  8  61.5  31.6  86.1  35.5  82.3  35.1  82.3
ARM  Residual Fragment (Treatment Group)  54  41  75.9  62.4  86.5  63.1  85.4  63.0  85.3

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and zero analyses. It does not report a statistical analysis plan identifying a primary testing hierarchy, adjustment for multiple comparisons, or the handling of multiple outcomes or participant groups. The registry does name a primary endpoint, but the multiplicity strategy is not reported in the registry record. Without a posted plan and results, it is not possible to determine whether any statistical adjustment was intended or applied.

Missing-data methods are also not reported in the registry record. The primary endpoint applies to participants exposed to at least one ultrasonic propulsion burst, but the number exposed, the number with evaluable imaging, and the number with missing or unclassifiable assessments are not posted. The record does not say how incomplete procedures, absent video confirmation, or uncertain motion observations would be treated. These details affect the denominator and interpretation of a participant percentage.

The record does not report whether analyses followed an intention-to-treat, per-protocol, or other analysis-population definition. Because the primary population is described by exposure to at least one burst, it is not possible to determine whether other enrolled participants were excluded from the endpoint population or how such exclusions were handled. Planned interim analyses and the statistical approach to subgroup results are not reported in the registry record.

General statistical context: Testing several outcomes or groups can increase the chance of at least one apparently notable result when each is assessed separately. A prespecified hierarchy or adjustment can address some multiplicity concerns, but the appropriate approach depends on the questions and design. Missing observations can also affect the result if they are related to the chance of meeting the endpoint. These are general considerations; the registry does not report enough analysis detail to determine how they apply to the posted study results.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: atrial fibrillation (6.2%).

The registry reports serious adverse events, other adverse events, and deaths separately for seven named groups. For serious adverse events, the listed at-risk and affected counts are: First in Human (FIH), 15 and 0; De Novo Small Stone, 2 and 0; Concurrent With URS, 18 and 1; Obstructing Stone - Pushing Only, 16 and 1; Obstructing Stone - Dislodging + Pushing, 13 and 0; Residual Fragment (Treatment Group), 54 and 0; and Residual Fragment (Control Group), 54 and 0. Deaths are listed as 0, 0, 0, 0, 0, 1, and 3, respectively. These are group-specific counts as recorded, not comparative effect estimates.

For other adverse events, the at-risk and affected counts are, in the same group order, 15 and 3; 2 and 0; 18 and 2; 16 and 1; 13 and 6; 54 and 31; and 54 and 20. The registry lists atrial fibrillation at 6.2% among the top serious terms. It does not report the denominator or additional context for that percentage.

General statistical context: Counts of affected participants describe how many people were recorded with an event; they do not describe event severity beyond the category assigned, timing, duration, or causal relation to the intervention. Group counts should not be compared as if the groups were randomized and otherwise equivalent. The registry’s overall design classification is nonrandomized, and it cautions against treating the arms as a like-for-like control comparison. Further event-level details and adjusted safety analyses are not reported in the registry record.

13. What the Result Does, and Does Not, Mean

The registry record establishes the study’s question and intended measurement: whether stone motion was visible on real-time ultrasound after exposure to ultrasonic propulsion. It also describes several participant settings and reports group-level adverse-event counts. It does not report the observed primary endpoint result, its denominator, or an uncertainty interval. The record therefore does not quantify how often motion was observed or how precisely that frequency was estimated.

The endpoint is evidence of observed movement, not a direct measure of whether a stone passed, symptoms changed, retreatment was avoided, or later symptomatic events were reduced. Those possibilities appear as aims in the study description, but results for them are not reported in the registry record. The distinction matters because a device can be evaluated on a process measure without that measure alone establishing a downstream clinical outcome.

The study’s overall nonrandomized, single-group classification also limits what can be concluded about comparative effects. The registry specifically says the arms are not a like-for-like control comparison. Counts in the residual-fragment treatment and control groups should not be treated as a reliable causal contrast on the basis of their labels alone. No comparative analysis is posted.

General statistical context: An observed outcome, its precision, and its causal interpretation are separate questions. A result can be estimated imprecisely, or measured in a design that does not support a strong comparison. Conversely, absence of a result in a registry record is not evidence that the outcome did or did not occur. Here, no primary result is posted, so neither the magnitude nor precision of the endpoint can be assessed.

The safety counts describe events recorded in each group, but do not by themselves establish whether an event was caused by the intervention. The record does not supply the event-level timing or attribution details needed for that assessment. Overall, the available information supports a description of the study design, endpoint definition, and listed safety figures, but not a conclusion about efficacy, comparative benefit, or causal safety effects.

14. Why This Trial Matters Statistically

Statistically, this study illustrates the difference between a clearly stated measurement and a reported result. The registry defines a participant-level endpoint based on observed stone motion and specifies the intended assessment timing and confirmation method. Yet it posts no primary endpoint estimate or analysis. A careful reading must keep the protocol question separate from evidence answering that question.

The study also spans several clinical settings, from small stones under observation to obstructing stones and residual fragments. This breadth makes the context of each group important: the participants, intended goals, and procedures differ. A pooled summary, if one were reported, would require careful interpretation because it could combine distinct settings. The registry does not report an analysis explaining how these groups were handled or whether subgroup results were planned.

The design classification is another important statistical feature. Although some group descriptions use treatment and control labels, the overall record identifies a nonrandomized, single-group study and warns against treating the arms as a like-for-like comparison. This is a reminder that group labels do not establish exchangeability or eliminate confounding. The allocation process and comparative analysis needed to evaluate group differences are not reported in the registry record.

General statistical context: Statistical reporting is most informative when it connects a prespecified question to the analysis population, estimate, uncertainty, missing-data handling, and design limitations. Counts and percentages can be useful descriptive evidence, but they do not automatically support a causal claim. Planning calculations are also distinct from observed outcomes and should be understood through their assumptions.

This record is therefore instructive about endpoint interpretation, design classification, and the limits of registry-level safety counts. It shows why statistical conclusions depend not only on the question a study asks, but also on what results and analysis details are made available.

15. 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 endpoint result is not reported in the registry record, and no analysis is listed. The number of participants assessed for stone motion, the endpoint denominator, and any estimate of uncertainty are also not reported. The listed enrollment of 172 does not establish how many participants contributed to the primary endpoint.

The overall design is classified as nonrandomized and single-group. The registry cautions that the arms are not a like-for-like control comparison, despite treatment and control labels in the residual-fragment descriptions. The record does not explain the allocation process across all groups or provide a comparative analysis. Accordingly, the group labels alone cannot support a causal interpretation.

The study includes multiple population groups with different clinical contexts and stated aims. The registry does not report how results were to be combined across these groups, whether subgroup analyses were planned, or how differences in group composition were addressed. The masking field says single, but the identity of the masked parties and practical details of masking are not reported.

The primary endpoint depends on observing motion on real-time images and confirming it by video review. Procedures for classifying ambiguous observations, resolving disagreement, or handling missing video are not reported in the registry record. The statistical plan, multiplicity approach, missing-data methods, analysis-population definitions, interim analyses, and sample-size justification are also not reported. The listed planning assumptions are described as illustrations based on the observed effect, rather than as the study’s own design plan.

Safety information is presented as group-level counts, without the event-level details, timing, or attribution needed for a fuller interpretation. The context and denominator for the listed atrial fibrillation percentage are not reported. These limits constrain interpretation of both the primary question and the safety record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety and Effectiveness of the Ultrasonic Propulsion of Kidney Stones — NCT02028559.
• Registry record last updated 2026-06-01; status last verified 2026-03.
• Results first posted 2026-06-01.
• 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.

19. Record Summary

The registry describes NCT02028559, “Safety and Effectiveness of the Ultrasonic Propulsion of Kidney Stones,” sponsored by the University of Washington. It lists enrollment of 172, phase as not applicable, nonrandomized allocation, a single-group model, and single masking. The status is active, not recruiting; the listed start date is 2013-12-17 and the primary completion date is 2025-08-01.

The study includes several participant groups and lists Propulse 1 with C5-2 and SC-X probes. Its primary endpoint is the percentage of exposed participants for whom stone motion is observed on real-time ultrasound images, with video review intended for confirmation. The record lists four outcome measures and zero analyses. The primary endpoint result and its analysis denominator are not reported in the registry record.

Group-level serious and other adverse-event counts and deaths are listed. The overall design is nonrandomized, and the registry cautions that the arms are not a like-for-like control comparison. The statistical analysis plan, missing-data methods, multiplicity approach, and comparative results are not reported.