High Frequency Stimulation Trials in Patients With Precision Spinal Cord Stimulator System: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for High Frequency Stimulation Trials in Patients With Precision Spinal Cord Stimulator System (NCT02265848), a randomized phase 4 study. The primary outcome is Numeric Pain Rating Scale (NPRS).

2. Clinical Question

3. Trial Design

This was a randomized, single-blind, phase 4 crossover trial with 22 enrolled participants. The study concerned people who already had a Precision Plus spinal cord stimulation system implanted for chronic axial pain. Its stated aim was to compare conventional stimulation programming with high-frequency programming and assess efficacy and preferability for back and extremity pain relief. The registry lists high-frequency and low-frequency stimulation as the interventions.

The study record describes two treatment sequences. Group A began with high-frequency stimulation, while group B began with low-frequency stimulation. Each group description refers to a 3-week initial period, followed by turning off the device and a wash-off period of 7-10 days before proceeding. The available group descriptions are incomplete, so the precise details of the later treatment period and sequence are not fully reported in the registry record. The total study duration is described as 7 weeks.

Randomization assigns participants to treatment sequences by chance; it does not mean that the treatment periods themselves are parallel comparisons. In a crossover design, participants may contribute measurements under more than one condition, and results can be affected by the order of conditions or by effects that persist after a treatment period. A wash-off period is intended to allow earlier treatment effects to diminish before the next period, but the record does not report how adequacy of wash-off was assessed.

The study was listed as completed. Its recorded start was 2014-10 and its primary completion was 2015-01. The sponsor was The Center for Clinical Research, Winston-Salem, NC. The identity of the person or persons masked, the full randomization procedure, and the detailed protocol 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: Randomization scheme was 1 to 1 ratio. Randomization assignment was generated using random number generator, and individual results were sealed in an envelope. If subject needed to be replaced, the replacement subject will receive the same randomization assignment.

Overall Study

Analysis population for the primary outcome, as defined in the registry: All study subjects were implanted with Boston Scientific's Precision Plus spinal cord stimulation system for treatment of chronic axial pain.

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.

6. Primary Endpoint

The registry lists the primary outcome as Numeric Pain Rating Scale (NPRS), measured over Baseline (visit 1), and at each follow up visits (visits 2, 3, and 4).

The primary endpoint was the Numeric Pain Rating Scale, or NPRS. The record describes a digital rating of subjective pain from 0 to 10, with higher values indicating progressively worse pain. This kind of scale gives participants a direct way to report perceived pain intensity, a symptom that cannot be measured solely by an external observer.

The planned measurements included baseline at visit 1 and follow-up visits 2, 3 and 4. Visits 2 and 4 captured measurements after treatment, with either 1000 Hz or standard stimulation depending on randomization. Visit 3 captured NPRS after the wash-off from spinal cord stimulation. The registry characterizes the endpoint using a mean and a full range, but it does not report the actual values for these visits.

Repeated measurements can help describe changes over time and differences associated with treatment periods. In a crossover study, the interpretation depends on which treatment each measurement followed, the order of the periods, and whether an earlier condition could still influence later scores. A comparison should therefore make clear how visits and treatment sequences were handled. That analysis is not reported in the registry record.

The endpoint is a measure of reported pain, not a direct measure of nerve activity, device performance, or every aspect of daily functioning. The registry lists the Oswestry Disability Index Questionnaire and Patient’s Global Impression of Change as secondary outcomes, but no results for these outcomes are reported.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several features of this trial affect what a valid statistical interpretation would require. The registry identifies the study as randomized, single-blind and crossover, and describes repeated NPRS assessments at baseline and follow-up visits. It does not report the statistical analysis plan, the model used for repeated measures, or a primary comparison. The following explains the general statistical issues raised by this design; it does not describe an analysis reported for this trial.

What does randomization contribute?

In general, randomization assigns treatment sequences by chance. It is intended to reduce systematic differences between sequence groups at the start of a study, including differences that could influence the outcome. Randomization does not guarantee that every characteristic will be balanced, particularly in a small study, and it does not remove the need to report how assignment was generated or concealed. The exact randomization procedure and allocation concealment are not reported in the registry record.

Because this is a crossover trial, the randomized assignment concerns sequence: group A began with high-frequency stimulation and group B began with low-frequency stimulation. A crossover comparison can use within-participant information, since a participant may receive both conditions. This can reduce the influence of stable differences between participants, but it makes treatment order and period relevant. The available descriptions do not fully specify the later treatment periods, so the full sequence cannot be reconstructed from the registry record.

Why do period and carryover effects matter?

In general, a period effect is a change associated with time or study period rather than with the stimulation condition itself. For example, pain ratings could shift over the course of participation for reasons unrelated to the assigned programming. A carryover effect occurs when an earlier treatment continues to affect outcomes during a later treatment period. A wash-off interval is intended to reduce such persistence, but it does not by itself demonstrate that carryover is absent. The record gives a wash-off period of 7-10 days and a visit after wash-off, but does not report an assessment of residual effects or a statistical method for handling them.

Repeated NPRS observations also require an analysis that recognizes that measurements from the same participant are related. In general, treating every visit as if it came from a different person can misrepresent uncertainty. Depending on the prespecified question and data structure, an analysis might compare treatment-period scores or changes, or model repeated measurements while accounting for participant-level dependence, time and sequence. The registry does not report which approach, if any, was used. No unreported model should be inferred from the endpoint description.

What would an estimate and confidence interval mean?

In general, an estimated treatment contrast expresses the observed difference between conditions on the chosen outcome scale. A confidence interval describes the uncertainty around that estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but interpretation also depends on the scale and the size of differences that are important to the research question. Here, the registry reports neither a contrast nor an interval. It is therefore not possible to describe the magnitude or precision of a comparative NPRS result.

A p-value, if reported, would address how compatible the observed data are with a specified statistical model and null hypothesis. It would not quantify the size or clinical importance of a difference. No p-value or testing procedure is reported. In particular, the absence of a reported p-value is not a result of no difference; it is an absence of a reported test.

How should the planning illustrations be understood?

In general, a sample-size planning illustration asks how many participants per arm would be needed under stated assumptions to detect a selected effect with a chosen power and significance level. Such an illustration is not a description of the trial’s observed results and is not observed power. The registry record says that its planning illustration is based on the observed effect, uses a two-sided significance level of 0.05 and equal allocation, and applies a normal approximation. It also states that the effect to detect is a selected fraction of the observed effect. Those assumptions describe an illustrative calculation, not the trial’s own design justification; the trial’s sample-size justification is not reported in the registry record. No particular planning value is interpreted.

In general, a calculation based on an observed effect can be sensitive to uncertainty in that effect, especially when the original study is small. It should not be read as proof that the study had adequate power or that a non-significant result would show equivalence. The registry’s stated planning method does not supply an outcome analysis or repair the absence of one.

What does the reported dispersion describe?

The primary endpoint is described as a mean with a full range. In general, the mean summarizes a set of values, while the range identifies the lowest and highest observed values. A range can be strongly influenced by extreme observations and does not communicate how values are distributed between its endpoints. Neither statistic alone establishes the uncertainty in a treatment contrast. The registry does not provide the endpoint values, so the variation in NPRS scores cannot be evaluated.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome assessed at baseline and several follow-up visits, and notes that the outcome has multiple categories or time points rather than a single reduced comparison. It also lists the Oswestry Disability Index Questionnaire and Patient’s Global Impression of Change as secondary outcomes. When multiple visits, outcomes or comparisons are examined, the chance of at least one apparently notable result can increase. In general, a prespecified primary contrast and a plan for handling multiple tests help readers distinguish the main question from exploratory comparisons. Any multiplicity adjustment or hierarchy of outcomes is not reported in the registry record.

The number of outcome measures is listed as four, while the number of analyses is listed as zero. This does not establish that no analysis was conducted outside the registry; it means that no analysis is recorded in the results details. The registry does not report test statistics, effect estimates or confidence intervals for the primary or secondary outcomes.

Missing-data handling is also not reported. The record gives the total enrollment and safety denominators, but does not state how many NPRS assessments were available at each visit, whether participants withdrew, or how incomplete measurements were handled. It does not identify an intention-to-treat, per-protocol or other analysis population. In general, missing outcomes can affect both the precision and the interpretation of estimates, and the implications depend on why measurements are missing and on the method used. Those details cannot be inferred from enrollment alone.

The registry record does not report interim analyses, stopping rules, imputation methods, sensitivity analyses, or a detailed statistical plan. These absences limit assessment of prespecification and robustness; they do not show that a particular analysis decision was made.

11. Safety Results

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

Other (non-serious) adverse events

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

The adverse-event group listings report 0 serious adverse events among 11 participants at risk in treatment group A and 0 among 11 at risk in treatment group B. The listings also report 0 other adverse events among 11 at risk in each group. No serious adverse-event terms are listed.

These figures describe the registry’s reported counts for the groups and denominators shown. They do not establish that no adverse events occurred outside the categories or recording period represented by these fields, and a count of 0 does not prove that an event is impossible. The registry does not report the adverse-event observation window, event definitions, severity assessment process, or whether participants contributed to both treatment periods in a way relevant to these group summaries.

The deaths field is not populated with a numerical count. A death total is therefore not reported in the registry record; it should not be read as a reported count of 0. The available figures are a limited safety summary and do not provide enough detail to characterize event timing, causes, relatedness, or differences between stimulation conditions.

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

The registry record describes a randomized crossover comparison of high-frequency and low-frequency spinal cord stimulation programming in 22 enrolled participants who already had a spinal cord stimulator. It identifies NPRS as the primary endpoint and gives the intended assessment visits and direction of the scale. It also reports group-level adverse-event counts. These details establish what the study was designed to examine and what measurements were recorded in the registry.

The record does not report an NPRS treatment estimate, its uncertainty, or a statistical test. Therefore, it cannot establish whether the pain ratings differed between conditions, the size of any difference, or whether the data were consistent with a range of possible effects. The lack of a reported comparison is not evidence that the treatments were equivalent, and it is not evidence that either condition improved pain. The stated study objective is not itself a result.

The crossover design means that participants were assigned to treatment sequences. Interpretation of a comparative result would depend on the treatment-period data, visit timing, order of treatment and handling of possible carryover. Those analysis details are not reported. The missing information also includes the number of outcome observations available at each visit and the analysis population, so the completeness of the pain data cannot be assessed.

The registry lists disability and global impression of change as secondary outcomes, but their results are not reported. It likewise does not describe a result for treatment preferability despite that being part of the official study title. The adverse-event counts should be read as the recorded counts for the listed groups, not as proof of an absence of risk.

In short, the available record supports a description of trial design, outcome measurement and limited safety counts. It does not support a conclusion about comparative efficacy, equivalence, patient preference or the precision of any treatment effect.

13. Why This Trial Matters Statistically

This trial is statistically notable because it uses a crossover structure to compare stimulation programming in participants who already had an implanted device. In general, crossover designs can make within-participant comparisons possible, which may be useful when stable differences between individuals influence the outcome. They also require careful attention to treatment order, period effects and whether an earlier condition continues to affect later measurements.

The registry describes a wash-off period and repeated pain ratings, making the timing of each observation central to interpretation. The presence of several visits does not by itself identify a single treatment contrast. A clearly specified analysis is needed to distinguish post-treatment measurements from the wash-off assessment and to account for the sequence each participant received. Those details are not reported in the registry record.

The trial also illustrates why a completed status and a stated endpoint are not substitutes for posted statistical results. Without estimates and uncertainty measures, readers cannot judge the magnitude or precision of a comparative effect. Without reported missing-data and analysis-population details, they also cannot assess how well the analyzed observations represent enrolled participants.

Finally, the record’s planning illustration is distinct from observed trial evidence. In general, planning calculations describe assumptions about a future or hypothetical detectable effect; they do not establish that a completed trial demonstrated an effect, nor do they provide observed power. Separating design, analysis and interpretation is especially important when the registry documents a clinical question but does not report an outcome comparison.

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 statistical interpretation is that the registry does not report numerical primary-outcome results or an analysis. The endpoint is identified as NPRS, but there are no visit-level summaries or treatment contrasts, and the record explicitly notes that the multiple time points were not reduced to one comparison. There is consequently no estimate of effect or precision to interpret.

The crossover sequence descriptions are incomplete. They identify the initial stimulation condition for each group and a wash-off period, but the later-period details are truncated. The full sequence, analysis of period and order, and assessment of possible carryover are not reported in the registry record. A wash-off interval is described, but its success in limiting residual treatment effects is not documented.

Although enrollment is 22, the number of participants with NPRS data at each visit is not reported. Withdrawals, missing assessments, analysis populations and methods for handling missing data are also not reported. The registry does not identify who was masked or provide sufficient detail to assess the implementation of blinding. A sample-size justification for the trial is not reported; the record’s planning illustration is described as based on the observed effect and is not the trial’s own design justification.

Results for the listed secondary outcomes and treatment preference are not reported. Safety counts have limited detail, including no populated numerical deaths count and no reported event observation window. These omissions restrict assessment of outcome robustness and safety context. They do not establish that any unreported procedure or analysis was absent, only that it is not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: High Frequency Stimulation Trials in Patients With Precision Spinal Cord Stimulator System — NCT02265848.
• Registry record last updated 2016-10-25; status last verified 2016-09.
• Results first posted 2015-11-11.
• 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.

18. Record Summary

The registry identifies NCT02265848 as a completed, randomized, single-blind, phase 4 crossover study of high-frequency and low-frequency spinal cord stimulation programming. It enrolled 22 participants with an implanted Precision Plus system for chronic axial pain. The recorded start was 2014-10, with primary completion in 2015-01.

The primary outcome was NPRS, assessed at baseline and follow-up visits. Secondary outcomes included the Oswestry Disability Index Questionnaire and Patient’s Global Impression of Change. The record describes treatment sequences and a wash-off period, but the available sequence details are incomplete.

No primary or secondary outcome analysis is reported. Serious and other adverse-event counts are listed as 0 in each group, with 11 participants at risk per group; a numerical death count is not reported. The registry record therefore documents the study design and selected safety counts, but not a comparative outcome estimate.