Effect of the Temperature Used in Thermal Radiofrequency Ablation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of the Temperature Used in Thermal Radiofrequency Ablation (NCT02148003), a randomized na study. The primary outcome is Visual Analog Scale (VAS) Pain Score 30-day After Procedure.

2. Clinical Question

The trial record describes a randomized, triple-masked, parallel study of thermal radiofrequency ablation. Its stated objective was to determine whether ablation at 90 degrees Celsius provides more overall pain relief, expressed as percent improvement, than ablation at 80 degrees Celsius without additional adverse events. The posted primary outcome, however, is the Visual Analog Scale pain score at the 30-day follow-up visit. The registry record does not report a posted primary result expressed as percent improvement.

The primary outcome data give a mean score of 50.4 for the 90-degree group and 47.2 for the 80-degree group. The reported comparison is framed as the 80-degree group minus the 90-degree group. These are group averages at follow-up, not a reported comparison of each participant’s improvement from a baseline score. The registry record does not report baseline scores in the posted outcome, so the change in score over time cannot be established from these figures.

The statistical question is therefore narrower than whether either procedure is beneficial: it concerns the observed difference between group mean pain scores at 30 days and the uncertainty around that estimate. Lower scores correspond to less pain on the described scale, but the posted means alone do not establish what caused the scores or whether a difference is clinically important. The record does not report a threshold for clinical importance.

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group trial comparing two temperatures for lumbar facet medial branch radiofrequency ablation. One arm received ablation at 90 degrees Celsius and the other at 80 degrees Celsius. The study status is terminated. The registry record reports enrollment of 199, but does not explain how that enrollment relates to the participants contributing to the posted primary outcome.

The posted outcome summaries list 59 participants for the 90-degree group and 58 for the 80-degree group. These are the group counts attached to the reported outcome summaries; they should not be taken as a complete account of enrollment, randomization, follow-up, or the analysis population. The record does not report a participant-flow description or explain why the outcome counts differ from the enrollment figure.

Triple masking is reported, but the registry record does not identify which people were masked or describe how masking was maintained. It also does not report details of sequence generation, allocation concealment, the procedure beyond the listed temperature and device, or adherence to assigned treatment. Those details cannot be inferred from the design labels.

The registry lists one outcome measure and no posted analyses. The primary outcome is the Visual Analog Scale pain score at the 30-day follow-up visit. The outcome description says participants marked a position on a strip and that the mark was translated to a score from 0, indicating no pain, to 100, indicating the worst imaginable pain. The registry record does not report the trial’s original statistical analysis plan, the rationale for its planned enrollment, or the reasons for termination. The presence of posted arm summaries and a comparison does not provide those missing design details.

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.

Population: 58 patients received RFA at 80°C and 59 patients received RFA at 90°C.

6. Primary Endpoint

The registry lists the primary outcome as Visual Analog Scale (VAS) Pain Score 30-day After Procedure, measured over 30 days after the procedure.

The primary endpoint is the Visual Analog Scale pain score 30 days after the procedure. Participants marked a position on a strip to indicate pain intensity; the mark was translated to a score from 0 to 100. A score of 0 represents no pain and 100 represents the worst imaginable pain. The registry describes the outcome as a continuous measure and reports its mean and standard deviation in each group.

A pain scale gives a structured way to record a subjective experience. The numeric score supports summaries across participants and a comparison of group averages. The mean describes the average score in a group, while the standard deviation describes how spread out individual scores are around that average. The endpoint is assessed at a stated follow-up time, which makes the comparison specific to the 30-day visit rather than to pain at all times.

As a general statistical point, a score measured at follow-up does not by itself quantify change from before treatment. A comparison of follow-up means and a comparison of changes from baseline are different analyses. The registry record does not report baseline values or a primary outcome analysis based on change. It also does not report a threshold for what size of difference would be clinically important. Consequently, the endpoint helps describe pain scores at follow-up, but the posted record alone cannot establish the clinical meaning of a particular difference or the course of pain over time.

7. Results Posted in the Registry

• RFA at 80 Degrees Celsius: mean 47.20 versus 50.40 on control; difference -3.20 (95% CI -14.42 to 8.02), standardized effect d = -0.10; z-test p = 0.576.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s pain intensity is represented by a numeric score, and the registry reports a group mean and standard deviation. The mean is the arithmetic average of the scores represented in that group summary. The standard deviation describes the typical spread of scores around the mean; it is not the uncertainty in the mean itself. In these results, the standard deviations are 31.4 in the 90-degree group and 30.5 in the 80-degree group.

The comparison is a mean difference, defined in the posted result as the 80-degree group’s mean minus the 90-degree group’s mean. The reported estimate of -3.2 therefore means the observed 80-degree group average is lower than the observed 90-degree group average by that amount on the score scale. The sign depends on the order of subtraction. Reversing the order would reverse the sign, while the substantive comparison of the same two averages would be unchanged. The point estimate is an estimate from the observed outcome summaries, not a statement that every participant experienced a change of that size.

A confidence interval describes the range of values for the group difference that are reasonably compatible with the estimate under the statistical model and its assumptions. The reported interval extends from -14.42 to 8.016. Because it covers zero, values compatible with the interval include no mean difference as well as differences in either direction. The interval is more informative than the point estimate alone because it communicates the uncertainty in the estimated contrast. It does not give the probability that a particular treatment effect is true, and it does not guarantee that the true value lies within the interval.

The reported unadjusted p-value is 0.576. As a general statistical explanation, a p-value measures how unusual results at least as incompatible with a specified null hypothesis would be if that hypothesis and the test assumptions held. It is not the probability that the null hypothesis is true, nor a measure of the size or importance of a difference. “Unadjusted” indicates that the posted p-value has not been adjusted for multiple comparisons. The registry record reports one outcome measure and no posted analyses, but does not report a complete multiplicity plan or a prespecified analysis hierarchy.

Standard errors describe the estimated sampling uncertainty of each group mean. The posted standard errors are 4.088 for the 90-degree group and 4.005 for the 80-degree group. A standard error is distinct from a standard deviation: the standard deviation describes variation among observed scores, whereas the standard error describes uncertainty in an estimate of the mean. The registry’s comparison also reports a pooled standard deviation of 30.96. A pooled standard deviation combines group variability for a standardized comparison under the calculation used; it is not an additional clinical outcome.

As a general statistical point, combining variability across groups can be reasonable when the analysis assumptions support treating the group variances as comparable. If variability differs substantially, a method that does not impose equal variances may be preferable. The registry record does not report its full analysis plan or enough methodological detail to determine which assumptions were prespecified for the sponsor’s analysis. The statistical comparison should therefore be read as the result posted in the registry, not as a complete description of the analysis method.

Random allocation is intended, in general, to make treatment groups comparable on average with respect to measured and unmeasured factors, subject to how allocation was implemented and to chance. A randomized label alone does not establish that allocation was concealed, that all assigned participants were analyzed, or that follow-up was complete. The record reports randomization and triple masking, but does not describe the implementation, the people masked, or the analysis population. These omissions limit assessment of potential bias.

One general concern in continuous outcomes is whether a mean adequately represents the data. If scores are highly skewed or have influential extreme values, the mean and a conventional mean-based interval may not fully capture the distribution. The registry reports means and standard deviations but does not report score distributions, diagnostics, or an alternative robust analysis. This is not evidence that assumptions failed; it means the record does not allow them to be assessed.

The posted p-value and confidence interval concern the group mean contrast at the 30-day endpoint. They do not address the trajectory of pain, changes from baseline, or a longer-term treatment effect. A follow-up score and a change score answer different questions. Without posted baseline results and a change analysis, interpretation should remain focused on the reported scores at the stated visit. The record also does not report how missing outcome values were handled, whether any imputation was used, or whether sensitivity analyses assessed the effect of missing data.

As a general principle, a statistically nonsignificant result does not establish equivalence. Establishing that two treatments are sufficiently similar requires a prespecified margin for an acceptable difference and an analysis designed to assess that margin. The registry record does not report such a margin or an equivalence or noninferiority analysis. The mean difference, interval, and p-value therefore should not be recast as proof that the temperature groups are equivalent.

10. Confidence Intervals and Precision

The point estimate for the difference in mean 30-day pain score is -3.2, comparing the 80-degree group with the 90-degree group. Its reported confidence interval ranges from -14.42 to 8.016. The interval is wide enough to include zero and values on both sides of zero. This means the posted estimate does not precisely determine the direction of the group difference. The data are compatible with a lower mean in the 80-degree group, little or no mean difference, or a higher mean in that group within the stated interval.

Precision is about the uncertainty in an estimate, not whether a result is important. The interval’s width reflects uncertainty in the estimated contrast under the analysis used. The substantial group standard deviations—31.4 and 30.5—show that individual scores varied widely in relation to the mean difference. Variation among participants and uncertainty in the group comparison are related but distinct: the standard deviations describe score spread, while the confidence interval describes uncertainty in the contrast.

The reported unadjusted p-value is 0.576, consistent with the interval including zero. Neither statistic establishes that the groups are identical. Conversely, the interval’s inclusion of effects in either direction does not demonstrate that all such differences are clinically important. The registry record does not report a clinical-importance threshold against which to judge the interval.

The outcome counts attached to the summaries are 59 in the 90-degree group and 58 in the 80-degree group. The record does not explain the relationship between those counts, the enrollment figure, missing observations, and the analysis population. That missing information makes it difficult to assess how outcome availability may have affected precision or introduced bias. The reported interval should be interpreted as uncertainty for the posted comparison, not as a guarantee about results in another population or at another follow-up time.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. This is a continuous-outcome comparison; the registry’s planning assumptions specify a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. The figures are planning illustrations calculated from the observed effect, not the trial’s original design assumptions, which are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm for a design with 80% power to detect the effect fraction in that row under those assumptions. The 90% power column gives the corresponding planning number for 90% power. Power describes a design’s chance of detecting an effect of the specified size if that effect is real and the model assumptions hold; it is not a guarantee of a statistically significant result.

The planning display considers 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For 100% of the observed effect, the figures are 1,470 participants per arm for 80% power and 1,967 participants per arm for 90% power. For 75% of the observed effect, they are 2,612 participants per arm for 80% power and 3,497 participants per arm for 90% power. For 50% of the observed effect, they are 5,877 participants per arm for 80% power and 7,867 participants per arm for 90% power.

Smaller effects are harder to distinguish from random variation, so the planning calculations require more participants per arm for smaller fractions of the observed effect. These figures are not observed power and do not explain why the trial enrolled the number it did or why it was terminated. The registry record does not report the original sample-size justification or its assumptions.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -3.200; pooled standard deviation σ = 30.957.
2. n = 2 × (1.96 + 0.842)² × 30.957² / -3.200² = 1,469.1, rounded up to 1,470 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -3.2                      # observed difference in means
sigma <- 30.9571836152985                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2148003)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 1,470 (80% power), 1,967 (90% power)
 75% of observed effect: n per arm = 2,612 (80% power), 3,497 (90% power)
 50% of observed effect: n per arm = 5,877 (80% power), 7,867 (90% power)
power.t.test: 1470.1 
Simulated power at n = 1,470 per arm: 0.798 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when an analysis makes several statistical comparisons or evaluates several outcomes. The more opportunities there are to find a seemingly unusual result, the greater the chance of at least one false-positive finding if each comparison is treated separately. Statistical approaches can address this, but the choice depends on which outcomes and comparisons were planned and on the scientific question.

The registry lists one outcome measure and no posted analyses. The comparison reports an unadjusted p-value of 0.576. That value should be understood as unadjusted, not as a multiplicity-controlled result. The registry record does not report whether additional outcomes or comparisons were planned in the original protocol, how a primary analysis was selected, or whether any adjustment strategy was specified. The absence of posted secondary results does not establish that no other analyses were planned or conducted.

The registry record also does not report how missing primary outcome values were handled. It does not specify whether all randomized participants were included, whether the analysis followed assigned groups, whether any participants were excluded, or whether imputation or sensitivity analyses were used. The reported outcome counts identify the participants represented in the summaries, but do not by themselves define the analysis population or explain missingness.

These omissions matter because analysis choices can affect both the estimated difference and its uncertainty. As a general point, missing outcomes can bias a comparison when the likelihood of being observed is related to outcome values or differs between groups. The direction and size of any such influence cannot be inferred without information about missingness and the methods used. The record also does not report a prespecified plan for handling deviations from the assigned procedure, protocol violations, or other analysis decisions.

Accordingly, the posted comparison can be interpreted as the registry-reported contrast of 30-day scores, but the record does not provide enough information to establish how comprehensive or prespecified the analysis was. The details of multiplicity control, missing-data handling, and analysis populations are not reported in the registry record.

14. 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 non-serious adverse event terms

The registry reports zero serious adverse events affected in the 90-degree group, with 59 listed as at risk, and zero in the 80-degree group, with 58 listed as at risk. It also reports zero other adverse events affected in the 90-degree group, with 59 listed as at risk, and zero in the 80-degree group, with 58 listed as at risk. Deaths are reported as zero in both groups.

These are the registry’s reported counts for the safety categories and at-risk groups. A zero count means that no affected participants are recorded in that category in the posted results; it is not evidence that the risk is exactly zero. The record does not provide descriptions of the adverse-event collection period, definitions, severity criteria beyond the listed categories, or completeness of safety follow-up. It also does not report whether any events were considered related to the procedure.

The stated study objective mentions comparing pain relief without additional adverse events, but the posted safety counts alone cannot establish a comprehensive safety comparison. They should be read as reported counts, with the limits imposed by the registry’s missing details about ascertainment and follow-up.

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

The results describe average pain scores 30 days after the procedure in the two temperature groups. The 90-degree group mean is 50.4 and the 80-degree group mean is 47.2. The reported difference, defined as 80 degrees minus 90 degrees, is -3.2. This is a modestly sized point estimate relative to the observed spread of scores, but the registry record does not provide a threshold for deciding what difference would matter clinically.

The confidence interval extends from -14.42 to 8.016, so it includes zero and leaves uncertainty about the direction and size of the difference. The unadjusted p-value is 0.576. Together, these statistics do not establish a clear difference between the reported group means, but they also do not prove that the procedures have identical results. A finding that does not meet a conventional statistical-significance threshold is not the same as a demonstration of equivalence.

The result does not show that either procedure reduced pain from baseline, because the registry does not post baseline scores or a change-from-baseline analysis. It does not directly answer the stated objective of comparing percent improvement. It does not establish longer-term outcomes, explain individual experiences, or show whether any difference is clinically important. The registry record does not report an equivalence margin, a clinically meaningful threshold, or secondary outcome results.

The safety record lists zero serious adverse events, zero other adverse events, and zero deaths affected in the two groups. These reported counts are not proof that no adverse events occurred, nor do they establish comparative safety beyond the events and follow-up captured in the record. The trial’s terminated status and the lack of a reported reason, participant-flow account, and missing-data description further limit conclusions about completeness.

The appropriate interpretation is therefore descriptive and cautious: the posted summaries show similar-looking group averages at the stated visit, with an interval that permits differences in either direction. They do not establish benefit, lack of benefit, equivalence, or comprehensive safety.

16. Why This Trial Matters Statistically

This trial is statistically interesting because it compares two versions of a procedure that differ by the stated temperature, while measuring pain on a continuous scale. A continuous endpoint can retain more detail than a simple yes-or-no outcome, but individual pain scores vary substantially. The group means, standard deviations, and confidence interval need to be considered together to understand what the observed comparison can and cannot resolve.

The estimated mean difference is -3.2, and its confidence interval ranges from -14.42 to 8.016. This interval makes the uncertainty visible: the point estimate alone might suggest one direction, but the data are compatible with a range of values that includes zero and effects in the opposite direction. That distinction is important when interpreting a small p-value or a single headline estimate; neither should replace attention to the magnitude and precision of the comparison.

The registry’s stated objective refers to percent improvement, while the posted primary outcome is a score at a single follow-up visit. This distinction illustrates why the precise definition of an endpoint matters. A comparison of follow-up levels is not automatically a comparison of improvement, and a statistical result answers only the question encoded by the outcome and analysis that were actually reported.

The record also illustrates the value of reporting a complete analysis context. The available information identifies randomization, masking, a parallel design, group summaries, and safety counts, but does not report the original statistical plan, the analysis population, handling of missing outcomes, or reasons for termination. Those details are essential to judge whether the reported comparison addresses the planned question and how robustly it does so. The statistical importance lies not in a decisive conclusion, but in seeing how estimates, uncertainty, endpoint definition, and reporting completeness jointly shape interpretation.

17. 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 marks the study as terminated but does not report why. Enrollment is listed as 199, while the primary outcome summaries contain counts of 59 and 58 in the two groups. The record does not explain how these figures relate to one another, whether participants were lost to follow-up, or who was included in the reported comparison. This limits assessment of the completeness and representativeness of the outcome data.

The posted primary outcome is a 30-day pain score, but baseline scores and a change-from-baseline result are not reported. The stated objective refers to percent improvement, which is not the form of the posted outcome comparison. The record also does not report a clinically meaningful difference threshold, longer-term pain outcomes, or secondary outcome results.

Although randomization and triple masking are recorded, the registry does not describe allocation concealment, who was masked, or the procedures used to maintain masking. The original statistical analysis plan, sample-size justification, analysis populations, missing-data methods, and multiplicity strategy are not reported in the registry record. The reason for termination and any implications for planned follow-up are also not reported.

The safety results list zero affected participants in the reported categories, but the record does not describe the safety ascertainment period, event definitions, or completeness of follow-up. These gaps mean the posted counts cannot establish that no events occurred beyond those captured in the registry. The limitations are constraints on interpretation; they do not demonstrate that any particular bias or problem occurred.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Effect of the Temperature Used in Thermal Radiofrequency Ablation — NCT02148003.
• Registry record last updated 2024-03-19; status last verified 2024-02.
• Results first posted 2024-03-19.
• 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.

21. Record Summary

The registry record describes NCT02148003, a randomized, triple-masked, parallel trial of lumbar facet medial branch radiofrequency ablation at 90 degrees Celsius versus 80 degrees Celsius. It lists low back pain as a condition, The Cleveland Clinic as sponsor, enrollment of 199, and a terminated study status. The record does not report the reason for termination.

The primary outcome is the Visual Analog Scale pain score 30 days after the procedure. The reported group means are 50.4 for 90 degrees Celsius and 47.2 for 80 degrees Celsius. The reported mean difference, comparing 80 degrees with 90 degrees, is -3.2, with a confidence interval from -14.42 to 8.016 and an unadjusted p-value of 0.576. The interval includes zero, and the registry does not report a clinical-importance threshold.

The safety record lists zero serious adverse events, zero other adverse events, and zero deaths affected in both groups. The registry lists one outcome measure and no posted analyses. Details about the original statistical plan, missing outcomes, analysis populations, and reasons for termination are not reported in the registry record.