Comparison of Electrotherapies for Chronic Low Back Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Electrotherapies for Chronic Low Back Pain (NCT01658735), a randomized na study. The primary outcome is Change From Baseline in Oswestry Disability Index at 1 Week.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group trial with triple masking and records its status as completed. Its official title describes a 12-week double-blinded randomized controlled trial, while the registry masking entry says triple. The record does not explain the difference between those descriptions or identify which trial roles were masked. The brief summary also describes the intended study as double-blinded.

The three device groups were H-Wave with usual care, TENS with usual care, and sham device with usual care. The registry lists enrollment of 113. For the primary outcome, the posted group sizes are 39 for H-Wave, 36 for TENS and 38 for sham electrotherapy. These are the reported counts for that outcome; the record does not describe participant flow or explain whether any enrolled participants were excluded from this analysis.

The primary endpoint was change from baseline in ODI at 1 week. The registry also lists changes in VAS pain score at 1 week, 4 weeks, 8 weeks and 12 weeks as secondary outcomes. The official title identifies a 12-week trial, but the primary outcome is an early measurement rather than the final listed follow-up.

The registry gives a start date of 2012-07 and primary completion date of 2013-10. It identifies the University of Utah as sponsor. A detailed protocol, the rationale for the planned enrollment, and the full operational description of the masking and randomization procedures 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.

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 Change From Baseline in Oswestry Disability Index at 1 Week, measured over 1 week.

The primary endpoint is mean change from baseline in the Oswestry Disability Index after 1 week of treatment. The ODI is a self-administered questionnaire intended to measure limitations in activities of daily living for people with low back pain. It has ten sections, each scored on a scale from 0 to 5, with 5 representing the greatest disability. The summed score is divided by the total possible score and expressed as a percentage on a scale from 0 to 100. Higher scores represent higher reported disability.

Using change from baseline describes how the score shifted during the first week, rather than relying only on the score measured at follow-up. A negative mean change indicates that the group’s average score was lower at follow-up than at baseline; in the context of this instrument, that direction corresponds to lower reported disability. It does not, by itself, show that a change was caused by the assigned device or that one group changed more than another.

The ODI is used as a patient-reported measure of disability related to low back pain. This endpoint captures reported functional limitations, which are distinct from pain intensity. The registry lists VAS pain changes as secondary outcomes, but those results are not included in the primary endpoint estimates.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: ODI change is expressed as units on a scale, and the registry reports a mean for each arm. A mean summarizes the group’s average observed change. It can be informative about the overall direction and size of change in a group, but it does not show the range of individual responses or how many participants improved, worsened or remained unchanged. Those details are not reported in the registry record.

What the confidence intervals express

Each arm’s mean is accompanied by a 95% confidence interval. In general, a confidence interval gives a range of values compatible with the data under the statistical method used and communicates uncertainty around an estimate. A narrower interval indicates greater precision under that method; a wider interval indicates less precision. A confidence interval is not a guarantee that the true value lies within that particular calculated range, and it does not describe where most individual participants’ changes fell.

For H-Wave, the interval runs from -4.56 to -0.45 around the mean change of -2.507. For TENS, it runs from -6.94 to -2.51 around -4.725. For sham electrotherapy, it runs from -6.94 to -2.56 around -4.752. The reported intervals are arm-specific. They are not confidence intervals for differences between arms, and they cannot be used alone to recover the trial’s intended comparison or its analysis method.

Why a direct group comparison matters

A randomized trial’s comparative question is generally addressed by estimating a contrast between assigned groups, with uncertainty around that contrast. The contrast could be defined in different ways depending on the prespecified analysis, such as a difference in mean change. This is a general explanation, not a claim about the model used in this trial. The registry record does not report a contrast estimate, a test statistic or a p-value for the primary outcome. The posted arm means therefore support description of each group’s change but not a definitive statistical conclusion about differences among the groups.

Separate intervals may overlap or appear separated, but that visual relationship is not itself the formal test of a treatment contrast. A direct comparison uses the uncertainty of the contrast, which depends on the variation and dependence structure in the data and on the analysis model. Details about those components are not reported in the registry record. No recalculated pairwise estimate is available in the listed results.

What would affect precision

In general, precision depends on the amount of information in the data and the variability of the outcome. Larger analysis groups can often estimate a mean more precisely when other conditions are similar, while more variable outcomes can make estimates less precise. The registry gives the number of participants contributing to the posted primary outcome for each arm, but it does not report the standard deviation or another measure of outcome variability. The confidence intervals provide the posted summary of precision without exposing the underlying variance estimate or calculation.

The sample-size assumptions recorded for planning illustrations are not the trial’s own design justification. They describe an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation and an effect set as a stated fraction of the observed effect. Such illustrations are hypothetical planning calculations, not observed trial outcomes or observed power. The registry record does not report the trial’s original sample-size justification or the assumptions used by investigators when planning enrollment.

Why over-dispersion can matter in count outcomes

Over-dispersion is a general issue for count data, where observed variability exceeds what a simple count model assumes. It can make uncertainty estimates too small if the model does not account for the extra variability. This is not the form of the primary endpoint: the primary outcome is a continuous mean change. The registry record does not report a count-based primary analysis or provide details suggesting that over-dispersion was relevant to the posted ODI result.

Although the registry labels the endpoint as a mean with a 95% confidence interval, it does not identify the exact statistical procedure used to construct the intervals. It also does not report whether the analysis adjusted for baseline ODI, used an intention-to-treat population, or handled repeated observations with a model. Those methods should not be inferred from the arm summaries alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary ODI change at 1 week and four secondary VAS pain change outcomes at 1 week, 4 weeks, 8 weeks and 12 weeks. It also records eight outcome measures in total, but provides only four secondary outcome names in the listed secondary outcome entry. The registry records zero analyses. It does not report a prespecified testing hierarchy, a multiplicity adjustment, or an explanation of how conclusions across outcomes and time points were to be controlled. When multiple endpoints or time points are examined, the chance of at least one apparently unusual result can increase; as a general statistical matter, the analysis plan determines how that issue is addressed.

The registry record does not report how missing primary outcome data were handled, how many participants had missing values, or whether the posted analysis included all randomized participants. The arm-specific primary outcome counts are 39, 36 and 38, but those counts alone do not establish the analysis population or explain losses between randomization and analysis. No imputation method, sensitivity analysis or missing-data assumption is reported.

The registry record also does not report whether analyses followed an intention-to-treat principle, whether participants were analyzed according to assigned group, or whether any per-protocol population was used. These details matter because exclusions or missing measurements can affect the balance created by randomization. The posted group summaries cannot resolve those questions.

Accordingly, the estimates should be read as the outcome summaries recorded for the stated arm counts, without assuming a particular multiplicity strategy, missing-data procedure or analysis population. The registry record does not report these elements of the statistical plan.

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.

Most frequent non-serious adverse event terms

For serious adverse events, the registry lists zero affected participants in each of the three groups: H-Wave, TENS and sham electrotherapy. The reported numbers at risk are 39 for H-Wave, 36 for TENS and 38 for sham electrotherapy. These are the recorded serious-event figures for the groups and should be read as registry summaries, not as proof that no serious events occurred outside the information captured in the record. No serious adverse event terms are listed.

The registry also records other adverse events affecting 2 participants in the H-Wave group, 2 in the TENS group and 1 in the sham group. The types of these events are not identified in the listed safety information. Death counts are not reported in the registry record.

These counts do not establish whether groups differ in safety, because the record does not provide a formal comparative analysis, detailed event descriptions, or the timing and severity of the other events. A count of affected participants is also distinct from a count of total events if one participant could have experienced more than one event; the registry record does not clarify that distinction. The figures describe what was posted, not a complete account of all possible harms.

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

The primary results show the average ODI change from baseline at 1 week in each assigned group. The group means were negative, and each arm’s 95% confidence interval was also on the negative side of zero. Because higher ODI scores indicate greater reported disability, this direction corresponds to lower average reported disability scores at that measurement. These are descriptive results for the groups and do not, by themselves, identify the cause of the changes.

The trial included H-Wave with usual care, TENS with usual care and sham electrotherapy with usual care. The central comparative question is whether the groups’ outcomes differed, but the registry record does not provide a direct between-group estimate or statistical test for the primary endpoint. The arm-level means should therefore not be treated as proof that one device outperformed another or that the groups were equivalent. A lack of a posted comparison is not evidence that no difference exists.

The outcome is an average change on a self-reported disability measure, not a direct measure of pain intensity, health care use or a participant’s individual experience. VAS pain outcomes are listed separately as secondary measures. The record does not give a threshold defining a clinically important ODI change, so the practical importance of the numerical mean changes cannot be established from the posted summaries alone.

The primary result concerns 1 week. It does not establish the pattern of ODI change across the full 12-week period, and the listed later outcomes concern VAS pain rather than later ODI. The registry record does not report the analysis details needed to assess adjustments, missing data or the exact construction of the confidence intervals.

The most defensible reading is limited to the posted descriptive evidence: the mean ODI score decreased from baseline in all three groups at the early measurement, with the stated uncertainty around each group mean. Claims about comparative effectiveness, durable change, individual benefit or clinical importance go beyond what the registry results establish.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between within-group change and a randomized comparison. Each arm has a mean change from baseline, but the trial’s comparative question requires an estimate of how those changes differ across assigned groups. A collection of arm-specific means and confidence intervals does not itself supply that contrast. Keeping the estimand clear helps prevent descriptive change from being mistaken for a treatment effect.

The study also illustrates why uncertainty should be reported alongside a point estimate. The means indicate the direction and average magnitude of change, while the 95% confidence intervals show that those estimates have uncertainty. The intervals apply to the group means, not to individual outcomes and not to between-group differences. Their interpretation depends on the statistical procedure, which is not described in the registry record.

The primary endpoint is an early disability measurement, while the study title and secondary outcome schedule concern a longer treatment period and pain scores at multiple follow-up times. Distinguishing outcome domains and measurement times is essential: a result for ODI at 1 week does not automatically answer a later pain question or a longer-term disability question.

Finally, the record’s lack of posted analyses, a detailed missing-data account and a multiplicity plan limits what can be concluded from the summaries. These gaps do not change the numerical estimates, but they constrain interpretation of their comparative and inferential meaning. Statistical reporting is most useful when it connects estimates to the prespecified question, analysis population and uncertainty method.

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 registry record offers limited detail about the design and analysis beyond the randomized, parallel and triple-masked entries. The official title and brief summary describe a double-blinded trial, whereas the masking entry says triple. The record does not explain this difference, identify who was masked, or describe how masking was maintained. Randomization methods and allocation concealment are not reported.

The posted primary endpoint is mean change at 1 week, with no reported direct comparison among the three arms. No p-value, contrast estimate or adjusted analysis is listed, and the registry records zero analyses. The confidence intervals describe arm means, not treatment contrasts. The record does not state how the intervals were calculated or whether baseline ODI was incorporated into the analysis.

Information about outcome variability, missing measurements, participant flow and the analysis population is not reported in the registry record. Although arm counts are listed for the primary outcome, the record does not explain whether these include all randomized participants or how missing data were addressed. The original sample-size rationale is also not reported.

The outcome schedule lists one primary ODI measurement and VAS pain outcomes at several follow-up times, but the registry does not report a multiplicity strategy. It does not provide later ODI results among the listed secondary outcomes. The primary result therefore cannot describe longer-term disability change.

Safety information is limited to counts of affected participants. Serious adverse event counts are posted as zero for each arm, but event descriptions are absent and death counts are not reported. Other adverse event types and a detailed safety analysis are not reported in the registry record. These limitations leave important aspects of outcome interpretation and trial conduct unresolved.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Electrotherapies for Chronic Low Back Pain — NCT01658735.
• Registry record last updated 2015-03-09; status last verified 2015-02.
• Results first posted 2015-03-09.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT01658735 is a completed randomized parallel-group trial sponsored by the University of Utah. It enrolled 113 participants with non-specific chronic low back pain and compared H-Wave with usual care, TENS with usual care, and sham electrotherapy with usual care. The registry lists triple masking, while the official title describes a double-blinded trial.

The primary outcome was change from baseline in ODI at 1 week. The posted means were -2.507 for H-Wave, -4.725 for TENS and -4.752 for sham electrotherapy, each with an arm-specific 95% confidence interval. The record does not post a direct comparison among arms or a statistical test for this endpoint. Four VAS pain outcomes at follow-up times through 12 weeks are listed as secondary outcomes.

Serious adverse event counts are recorded as zero in all groups. Additional detail about the statistical plan, missing data, analysis populations and comparative results is not reported in the registry record.