Effect of Pulse Width With Spinal Cord Stimulation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Pulse Width With Spinal Cord Stimulation (NCT00399516), a non-randomized phase 4 study. The primary outcome is Pain Severity, as Measured on the 11-point (0-10) Numerical Rating Scale (NRS).

2. Clinical Question

The study asked whether varying pulse width during suprathreshold dorsal column stimulation was associated with a change in pain severity in people with low back pain. Its stated primary objective was to assess the effects of varying pulse width. The registry record identifies the study as a single-group, non-randomized study, rather than a randomized comparison of different pulse-width strategies.

The primary measure uses the 11-point Numerical Rating Scale, whose endpoints are described as 0 for “no pain” and 10 for “worst pain imaginable.” The outcome is specified as a mean percent change in pain rating, with standard deviation as the measure of dispersion. The registry record does not report the observed mean, its standard deviation, or a confidence interval. It therefore does not provide a numerical estimate with which to answer the primary question.

3. Trial Design

The registry record describes a Phase 4, completed, non-randomized, unmasked, single-group study sponsored by Boston Scientific Corporation. The intervention is the Precision spinal cord stimulation device. The enrollment is 21. The recorded start is 2006-11, and the primary completion is 2007-10. These details describe the registered study structure; they do not establish how participants were assigned to particular programming settings or how long each setting was used.

The brief summary states that the primary objective was to assess the effects of varying pulse width in suprathreshold dorsal column stimulation in patients with low back pain. However, the design fields specify a single group and non-randomized allocation. No randomized parallel control group is identified, and the registry record does not describe a separate comparator. The listed design therefore cannot be treated as a randomized between-group trial of pulse-width settings. Any interpretation of variation across settings would depend on procedural details that are not reported in the registry record.

Masking is listed as none. The record does not describe whether outcome collection, data processing, or any other study procedures were blinded. Specific participant characteristics, eligibility criteria, the number or sequence of programming settings, and the timing of pain assessments beyond the stated outcome timeframe are not reported in the registry record. Neither the protocol details nor the rationale for the enrollment target are reported in the registry record.

The primary outcome is pain severity measured on the Numerical Rating Scale and reported as percent change in pain rating within 6 months post-implantation. The measure is continuous, and its summary is specified as a mean with standard deviation. One primary outcome measure is listed, but the registry record reports no analysis results. The study status is completed; completion status alone does not provide an estimate of the outcome or establish what the findings were.

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

Reasons for not completing this period:

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 Pain Severity, as Measured on the 11-point (0-10) Numerical Rating Scale (NRS), measured over Within 6 months post-implantation.

The primary endpoint is pain severity measured with the 11-point Numerical Rating Scale. The registry description defines 0 as “no pain” and 10 as “worst pain imaginable.” The listed outcome unit is percent change in pain rating, summarized as a mean with standard deviation, with a timeframe of within 6 months post-implantation. The registry record does not report the observed percent change or its variability.

General explanation: a numerical rating scale turns a person's reported symptom intensity into an ordered numerical response. Repeated ratings can be summarized to describe the direction and size of change over time. Expressing change as a percentage is intended to relate the change to a reference rating, but interpreting that quantity requires knowing how the reference and follow-up values were defined and handled. Those calculation details are not reported in the registry record.

A mean describes the average outcome across the observations included in an analysis. Standard deviation describes how spread out those observations are around the mean; it is not the same as the uncertainty around the mean. A confidence interval, if reported, would describe uncertainty in an estimated quantity under the assumptions of the statistical method. No confidence interval is reported in the registry record.

Pain ratings are used as patient-reported measures because pain severity is an experience reported by the person experiencing it. The registry description gives the scale endpoints, but does not report additional measurement properties, the assessment schedule, or the analysis population. The listed timeframe also does not establish the exact assessment visit or whether all participants contributed a measurement in that interval.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a continuous measure summarized by its mean and standard deviation. It does not report the analysis itself. The explanations below describe general statistical concepts; they are not claims about unreported methods used in this study.

What does a mean summarize?

General explanation: the mean is the arithmetic average of the observations included in an analysis. For a continuous outcome such as a numerical pain rating or a change derived from ratings, it gives a central summary across the analyzed observations. Its interpretation depends on what was measured, when it was measured, and which participants contributed data. The registry record identifies percent change in pain rating as the outcome, but does not give the formula used to calculate that percent change or specify the analysis population.

A mean can be affected by unusually high or low observations. It also does not show whether individual observations cluster closely around the average or vary widely. The standard deviation provides a summary of that spread. It describes dispersion among observations, not the precision of the mean estimate. The registry record lists standard deviation as the dispersion measure but does not report its value.

How is uncertainty different from variability?

General explanation: variability concerns how different the observed outcomes are from one another. Uncertainty concerns how precisely a sample-based estimate represents the quantity being estimated. A confidence interval is one way of expressing uncertainty around an estimate under specified statistical assumptions. A narrow interval indicates greater precision than a wide interval, but neither width nor the interval's position alone establishes that a result is clinically important. No confidence interval or other uncertainty interval is reported in the registry record.

When a confidence interval is available, its interpretation relies on the design, analysis method, and assumptions used to calculate it. For a single-group study, an interval around the mean change would describe uncertainty in that group's estimated change, not the effect relative to a randomized control group. A within-group estimate and a between-group treatment contrast answer different questions.

Why does the design affect interpretation?

General explanation: random assignment can help create comparable groups by distributing known and unknown factors across treatment conditions. A non-randomized, single-group design does not provide that protection through randomized allocation. If outcomes are compared across measurements or programming conditions within one group, the interpretation may depend on order, timing, carryover, and other aspects of the procedure. These are general considerations, not a description of what occurred in this trial. Specific details about setting sequence, duration, and analysis are not reported in the registry record.

Masking can also affect the measurement process or the conduct of a study, depending on who is masked and to what. The registry lists masking as none, but does not describe how pain ratings were collected or whether anyone involved in data handling was masked. It would be inappropriate to infer additional procedures from the masking field alone.

What do the planning assumptions mean?

General explanation: sample-size planning uses assumptions about the effect to be detected, outcome variability, significance level, allocation, and statistical method. The registry record describes planning illustrations based on an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the target effect is a stated fraction of the observed effect. The illustrations are planning quantities, not measurements from participants and not observed power.

The assumptions refer to a two-arm planning framework, whereas the registered study is described as single-group and non-randomized. They should therefore not be taken as a description of the study's actual design. The observed effect used as a planning input is not reported in the registry record, and no planning output should be read as a study result.

What information is needed to assess the analysis?

General explanation: a complete assessment of an outcome analysis typically requires the estimate, its uncertainty, the number of observations contributing to it, and a clear account of the analysis population and missing-data handling. The registry record does not report those outcome details. It also does not report the statistical model, any covariate adjustment, assumptions checks, or an analysis plan. No inference should be made about these methods from the listed mean and standard deviation alone.

The record lists zero analyses and no numerical primary outcome result. Consequently, there is no posted inferential analysis to interpret for the primary endpoint. The design and endpoint definitions can be described, but they cannot substitute for the missing estimate and its uncertainty.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Spinal Cord Stimulation Programming Parameters")
n   <- c(19)
m   <- c(-56.1)
sp  <- c(25.8)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Spinal Cord Stimulation Programming Parameters  19  -56.100  25.800  -68.535  -43.665

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure: mean percent change in pain rating on the Numerical Rating Scale within 6 months post-implantation. It does not report a statistical analysis result for that outcome. Although one primary measure is listed, the record does not describe whether additional outcomes or exploratory analyses were planned, or how any multiple testing would have been handled. A multiplicity strategy is not reported in the registry record.

General explanation: multiplicity arises when several hypotheses or outcomes are tested. Testing many hypotheses can increase the chance of at least one apparently notable result by chance. Statistical approaches can address this concern, but the appropriate approach depends on which analyses were planned and how they relate to one another. No such approach can be inferred from the registry information.

The analysis population is not reported in the registry record. The enrollment is 21, but the record does not state how many participants contributed outcome observations, whether any participants were excluded from analysis, or what rules defined inclusion. Missing-data amounts and reasons, methods for handling missing observations, and sensitivity analyses are also not reported in the registry record.

General explanation: missing outcome data can affect both the precision and the interpretation of an estimate, particularly if the likelihood of a missing measurement relates to the outcome. Statistical methods make different assumptions about missingness. Without information on observed data, missingness, and analysis choices, readers cannot determine which assumptions would be relevant or how robust a result might be.

The registry record does not report an interim-analysis plan, stopping rules, or a prespecified statistical analysis plan. These omissions do not establish that such procedures were absent; their details are not reported in the registry record. The posted record therefore does not permit an assessment of multiplicity control, missing-data handling, or the population used for the endpoint analysis.

12. 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.

Most frequent non-serious adverse event terms

The registry lists a group titled “Spinal Cord Stimulation Programming Parameters,” with 21 participants at risk for the serious adverse event field and 0 affected. For other adverse events, it lists 21 at risk and 2 affected. The record does not provide serious adverse-event terms; no top serious terms are listed. A death count is not reported in the registry record.

These figures should be read as registry counts, not as a complete account of the nature, timing, severity, or relatedness of events. The record does not describe the events affecting participants, whether events were assessed as related to the device or procedure, or how long safety was monitored. It also does not provide event-level details or a narrative explaining the group label.

General explanation: “at risk” denotes the recorded group used as the denominator for an adverse-event field, while “affected” is a count of participants recorded with an event in that field. These counts do not, by themselves, establish the probability of an event under other conditions or permit comparison with a control group. Because the study is listed as single-group and non-randomized, the adverse-event figures do not provide a randomized comparative safety estimate. The registry record does not report additional detail needed to interpret the counts beyond their recorded fields.

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

The registry record establishes that NCT00399516 was a completed, Phase 4 study of spinal cord stimulation programming for chronic low back pain. Its objective concerned varying pulse width in suprathreshold dorsal column stimulation, and its primary endpoint was mean percent change in pain rating on the Numerical Rating Scale within 6 months post-implantation. It also identifies the study as non-randomized and single-group.

The record does not report the primary outcome estimate, its standard deviation, a confidence interval, or a statistical test. It therefore does not show the direction or magnitude of pain-rating change, how variable the observations were, or how precisely any average change was estimated. A reader cannot determine from this record whether pain ratings increased, decreased, or remained similar over the stated timeframe.

The design also limits what can be concluded even if a within-group change were available. General explanation: observing a change within one group does not establish that the intervention caused that change. A comparator can help distinguish change associated with a treatment strategy from change that may occur for other reasons. The registry record does not identify a randomized comparator or provide a like-for-like control comparison.

The absence of a posted analysis does not mean that no analysis was conducted; it means that analysis results are not reported in the registry record. Likewise, the completed status does not supply an outcome estimate. The enrollment figure is not a substitute for the number analyzed, and the analysis population is not reported in the registry record.

The adverse-event fields record 0 participants affected in the serious-event field and 2 affected in the other-event field, each with 21 at risk. The registry does not report event descriptions, relatedness, or a death count. These figures are limited safety information, not a comparative assessment.

The defensible conclusion is narrow: the record describes the study question, design, endpoint, and selected adverse-event counts, but does not provide the outcome analysis needed to characterize the primary result. No conclusion about the magnitude, precision, or causal interpretation of a pain-rating change can be drawn from the registry record.

14. Why This Trial Matters Statistically

This trial matters statistically because its stated objective concerns changes in programming settings, while the registered design is non-randomized and single-group. That distinction is central to interpreting evidence. A study can measure an outcome and describe change, but the design determines which comparisons are supported and what causal interpretation is justified.

The endpoint also illustrates the difference between a scale's definition and an analysis result. The registry identifies the Numerical Rating Scale endpoints and specifies percent change as the outcome unit. Yet without the calculation details, outcome estimate, and variability, the clinical question cannot be answered quantitatively. A defined endpoint is necessary for interpretation, but it is not itself evidence about the observed result.

Another statistical lesson is the distinction between outcome spread and estimate precision. The registry specifies standard deviation, which would describe variation in participant measurements. It does not report a confidence interval or the analysis population. Even a reported average and standard deviation would require context about the number analyzed and the method before precision could be evaluated.

The record's sample-size assumptions also demonstrate why planning calculations should be separated from trial findings. Those assumptions describe a two-arm planning illustration based on an observed effect, while the trial design is listed as single-group. Planning illustrations are not observed power, and they do not provide evidence that the primary outcome changed. Their interpretation also depends on inputs that are not reported as outcome results in the registry record.

Finally, the sparse reporting underscores the importance of analysis details. Without results, missing-data information, and a description of the analysis population, readers cannot evaluate the primary endpoint statistically. The registry information supports a careful account of what was intended and how the study was classified, while also making clear the boundary between design information and evidence about outcomes.

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 central limitation of the registry record for interpreting this study is that it does not report the primary outcome result. There is no posted mean percent change in pain rating, standard deviation, confidence interval, or test result. The outcome's direction, magnitude, and precision therefore cannot be assessed.

The study is listed as non-randomized and single-group, with no masking. No randomized control group is identified. This limits the ability to attribute any within-group change to pulse-width variation rather than other influences. The registry record does not explain how different programming settings were ordered, how long settings were used, or whether outcomes were compared across settings.

Important population and analysis details are not reported in the registry record. These include eligibility criteria, participant characteristics, the number contributing outcome measurements, the analysis population, and how missing observations were handled. The record also does not specify the calculation used for percent change, the exact pain-assessment schedule, or whether the assessment was completed at a common time for participants.

The registry lists one primary outcome measure and zero analyses, but does not provide a statistical analysis plan, model, adjustment strategy, or multiplicity approach. The sample-size assumptions describe a two-arm planning illustration and do not establish the study's own design rationale. The protocol rationale for enrollment is not reported in the registry record.

Safety reporting is limited to counts of affected participants in serious and other adverse-event fields. Event descriptions, relatedness, monitoring details, and a death count are not reported in the registry record. These gaps prevent a fuller interpretation of either the primary endpoint or the adverse-event information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Effect of Pulse Width With Spinal Cord Stimulation — NCT00399516.
• Registry record last updated 2012-04-04; status last verified 2012-03.
• Results first posted 2012-04-04.
• 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

NCT00399516, “Effect of Pulse Width With Spinal Cord Stimulation,” is registered as a completed Phase 4, non-randomized, unmasked, single-group study sponsored by Boston Scientific Corporation. Its recorded start is 2006-11 and its primary completion is 2007-10. Enrollment is 21.

The study objective was to assess varying pulse width in suprathreshold dorsal column stimulation among patients with low back pain. The listed intervention is the Precision device. The primary outcome is mean percent change in pain severity on the 11-point Numerical Rating Scale within 6 months post-implantation, with standard deviation specified for dispersion.

The registry record does not report a primary outcome estimate or analysis. It lists 0 affected in the serious adverse-event field and 2 affected in the other adverse-event field, each with 21 at risk. Event descriptions and a death count are not reported in the registry record. The design does not identify a randomized control group, so the record does not support a like-for-like treatment comparison.