Lutonix® Drug Coated Balloon vs. Standard Balloon Angioplasty for Treatment of Femoropopliteal In-Stent Restenosis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Lutonix® Drug Coated Balloon vs. Standard Balloon Angioplasty for Treatment of Femoropopliteal In-Stent Restenosis (NCT02063672), a randomized na study. The primary outcome is Percentage of Participants With Primary Patency at 1 Year.

2. Clinical Question

The practical statistical question is how much information these observed proportions provide about the difference between the assigned balloon strategies. The primary outcome is a binary status assessed at 12 months, not a measure of how long each participant remained free of restenosis or revascularization. The registry record therefore supports interpretation of the proportions and their uncertainty at that follow-up point, rather than conclusions about the timing of events or longer-term outcomes. It also reports several secondary outcomes, including success measures during the index procedure and patency at other follow-up times, but the primary question is the 12-month primary-patency comparison.

3. Trial Design

This was a prospective, multicenter, randomized, controlled trial with a parallel-group design and single masking. Participants were assigned to Lutonix DCB or a standard uncoated balloon angioplasty catheter. The registry record lists the study phase as not applicable. It identifies C. R. Bard as the sponsor and records enrollment of 82 participants. The study start is recorded as 2014-03, the primary completion date as 2017-02-13, and the study status as completed.

Randomization is intended to make the treatment groups comparable, on average, with respect to factors that could affect outcomes. It does not guarantee that groups will be exactly alike in a small study, nor does it eliminate uncertainty in the outcome estimates. Single masking means that some parties involved in the study were masked, but which parties were masked and how masking was maintained are not reported in the registry record. The detailed randomization procedure, allocation concealment, and any stratification factors are also not reported in the registry record.

The primary endpoint population is described as all subjects who completed a 12-month follow-up visit. The posted primary outcome denominators are 49.0 for Lutonix DCB and 23.0 for the PTA catheter group. These are not the same as the overall enrollment count, and the record does not explain in detail why participants were not included in the primary endpoint denominators. The numbers analyzed may therefore reflect follow-up availability or another endpoint-specific population definition; the reason is not reported in the registry record.

The trial also lists device success, technical success, and procedural success during the index procedure, as well as further clinical and patency outcomes. Detailed eligibility criteria, treatment delivery rules, concomitant care, and the protocol’s original statistical plan are not reported in the registry record. The registry identifies the trial as randomized and single-blind but does not describe the operational details needed to assess each feature more fully.

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:

Analysis population for the primary outcome, as defined in the registry: All subjects who completed a 12-Month follow-up visit

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 Percentage of Participants With Primary Patency at 1 Year, measured over 12 Months.

The primary endpoint is the percentage of participants with primary patency at 1 year, assessed at 12 months. The registry definition treats primary patency as freedom from clinically driven target lesion revascularization (TLR) and freedom from binary restenosis. In other words, a participant counts as having primary patency only if neither of those endpoint events is recorded under the study definition. The endpoint is binary at the specified follow-up: each included participant is classified as meeting or not meeting the definition.

Patency is used to describe whether the treated vessel segment remains open without the specified failure events. Including clinically driven TLR captures an outcome that leads to a clinical decision to reintervene, while binary restenosis captures narrowing assessed by the study’s restenosis criterion. The exact threshold and assessment procedures for binary restenosis are not reported in the registry record. Nor does the record explain how missing assessments or incomplete information about either component were handled.

The primary result is based on participants who completed a 12-month follow-up visit, rather than all 82 enrolled participants. This matters because a proportion describes the participants included in its denominator. The reported values do not, by themselves, indicate when restenosis or revascularization occurred, how many participants experienced each component separately, or whether a participant had a different clinical course before the scheduled assessment. Those component-specific and time-to-event details are not reported in the registry record.

The endpoint is useful for a randomized comparison because it reduces each participant’s status to a common, clinically interpretable definition at a fixed follow-up time. Its summary is still only as informative as the completeness and consistency of follow-up and outcome assessment. The record reports a 95% confidence interval for each group, which helps convey the uncertainty around the observed proportions.

7. Results Posted in the Registry

• PTA Catheter: 47.8% (11/23) versus 67.3% (33/49) on control; risk difference -19.5 percentage points (95% CI -43.8 to 4.8), risk ratio 0.71 (0.44–1.14); unadjusted two-proportion z-test p = 0.113.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Percentage of Participants With Device Success

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • PTA Catheter: 100.0% (28/28) versus 98.1% (52/53) on control; risk difference 1.9 percentage points (95% CI -1.8 to 5.5), risk ratio 1.02 (0.98–1.06); unadjusted two-proportion z-test p = 0.465.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between PTA Catheter and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Participants With Technical Success

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • PTA Catheter: 77.8% (21/27) versus 66.0% (33/50) on control; risk difference 11.8 percentage points (95% CI -8.7 to 32.2), risk ratio 1.18 (0.89–1.56); unadjusted two-proportion z-test p = 0.281.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between PTA Catheter and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Participants With Procedural Success

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • PTA Catheter: 77.8% (21/27) versus 70.0% (35/50) on control; risk difference 7.8 percentage points (95% CI -12.4 to 28.0), risk ratio 1.11 (0.85–1.46); unadjusted two-proportion z-test p = 0.465.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between PTA Catheter and the control. The interval gives the range of effects that remain compatible with the data.

The registry record lists secondary outcomes spanning immediate procedural performance, patency during follow-up, revascularization, and sustained clinical benefit. Numerical results with group estimates and comparisons are posted for device success, technical success, and procedural success during the index procedure. The pattern across those available measures is not uniformly in one direction: device success was high in both groups, while the posted technical and procedural success percentages were numerically lower in the Lutonix DCB group. The comparisons for these endpoints are imprecise, with confidence intervals that include no difference.

These procedure-time outcomes address different aspects of treatment delivery from the primary 12-month patency endpoint. Device success, technical success, and procedural success are not interchangeable with freedom from clinically driven TLR and binary restenosis at 12 months. They can provide context about the index procedure, but they do not directly establish or explain the later patency result. Similarly, the additional listed outcomes concerning patency at other follow-up times, TLR, and clinical benefit concern related but distinct questions.

Although the record lists 18 secondary outcomes, the numeric result detail in the registry record is limited to some of those outcomes. The remaining secondary outcome results and the full set of analysis details are not reported in the registry record in the information summarized for this trial. A broad list of endpoints can reflect multiple clinical domains, but a list alone is not evidence of a particular pattern of results.

Secondary findings generally carry less weight than a prespecified primary comparison because they may involve more analyses, smaller endpoint populations, and greater opportunity for chance findings. The registry does not report whether a multiplicity adjustment was used or which secondary comparisons were prespecified for confirmatory inference. The posted unadjusted secondary p-values should therefore be treated as exploratory evidence rather than independent confirmation of the primary result. The primary result remains the principal randomized comparison for the trial’s stated primary question.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Percentage of Participants With Device Success
• Percentage of Participants With Technical Success
• Percentage of Participants With Procedural Success
• Percentage of Participants With Primary Patency at 6 and 12 Months
• Percentage of Participants With Secondary Patency at 6 Months and 12 Months
• Percentage of Participants Without Clinically Driven Target Lesion Revascularization (TLR)
• Percentage of Participants Without Target Lesion Revascularization (TLR)
• Percentage of Participants With Sustained Clinical Benefit Compared to Baseline

9. Statistical Interpretation

10. Statistical Methods Explained

The reported primary outcome is binary: a participant either meets the registry definition of primary patency at 12 months or does not. For a binary endpoint, the basic group summary is the number meeting the definition divided by the number included in that group’s endpoint population, expressed as a percentage. The registry reports 67.0% for Lutonix DCB and 49.5% for the PTA catheter group, with 49.0 and 23.0 participants in the respective denominators. A percentage is easier to interpret than a raw event count, but it does not convey its own precision; the confidence interval supplies information about that uncertainty.

What does the risk difference describe?

A risk difference subtracts one group’s event proportion from the other group’s event proportion. It is an absolute contrast on the proportion scale, unlike a risk ratio, which compares proportions as a ratio. For the primary comparison, the posted direction is PTA catheter minus Lutonix DCB. The estimated risk difference is -0.195. A negative value in this direction means the observed primary-patency proportion was lower in the PTA catheter group. The estimate should be interpreted alongside its 95% confidence interval, -0.438 to 0.048; the interval includes zero and therefore includes no difference as one value compatible with the data and method.

Risk differences are often clinically interpretable because they describe an absolute separation between group proportions. They can nevertheless be sensitive to the endpoint definition, follow-up time, and population included in each denominator. A comparison of proportions at 12 months is not the same as a comparison of event timing. The registry record does not report a time-to-event analysis for the primary endpoint, so no timing-based interpretation should be substituted for the posted binary comparison.

What does a confidence interval contribute?

A confidence interval is a range calculated by a statistical method to express the uncertainty around an estimate. In repeated use of the same method under its assumptions, intervals constructed in this way would cover the underlying parameter at the stated rate. It is not a range that assigns a probability to the fixed parameter after observing the data. The 95% confidence intervals around the group percentages and the risk difference show that the estimates are not sharply determined by the available endpoint data.

Interval width reflects, among other factors, the amount of information and the variability of the data. Small denominators generally produce less precise estimates of proportions, particularly when outcomes are uncommon or near the extremes of the scale. The PTA catheter group’s endpoint denominator is smaller than the Lutonix DCB denominator, and its primary-patency interval is broad. The risk-difference interval likewise extends across a range that includes both a meaningful negative contrast and a small positive contrast. This breadth cautions against treating the point estimate as an exact measure of the underlying difference.

How should the p-value be read?

The posted unadjusted p-value for the primary comparison is 0.113. A p-value measures how incompatible the observed data, or data more extreme under a specified test, are with a null hypothesis under the assumptions of that test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The test used, its detailed assumptions, and whether this comparison followed a prespecified analysis plan are not reported in the registry record. The p-value should therefore be read as an unadjusted summary, together with the estimate and interval, not as a stand-alone decision.

For a binary outcome, a test or interval procedure can depend on whether it uses a normal approximation, an exact method, or another approach. The registry record does not specify the method used for the primary comparison. The listed comparison is not marked as discrepant from the posted arm results, but that does not identify the procedure used or provide details about any protocol-defined primary analysis.

Why can the analysis population matter?

The primary endpoint population includes participants who completed a 12-month follow-up visit. If participants without a completed visit differ from those with one, a complete-follow-up summary may not represent all randomized participants. Statistical methods can address missing outcome data in different ways, but those approaches require assumptions and should be reported so readers can evaluate them. The registry record does not report an imputation method, a missing-data sensitivity analysis, or reasons for absent follow-up. As a result, the posted proportions should be understood as summaries of the stated follow-up population.

The reported endpoint denominators are not uniform across all outcomes. During-procedure secondary outcomes use different group sizes, and the adverse-event group counts differ from the primary endpoint denominators. This can occur because outcome definitions and analysis populations differ, but the exact reasons are not reported in the registry record. Comparisons should use the denominator and population specific to each outcome rather than assuming one common set of participants.

What does unadjusted mean in this setting?

An unadjusted comparison uses the group outcome data without accounting for other participant characteristics in a regression or stratified model. Randomization is designed to support a fair comparison, but adjustment can still be prespecified to improve precision or account for design features. The registry record does not report a covariate-adjusted primary model, randomization strata, or an analysis population beyond the completed-follow-up description. The posted unadjusted result is therefore the appropriate description of the available comparison, while the absence of further analysis details limits assessment of robustness.

11. Confidence Intervals and Precision

Precision concerns how narrowly the available data identify an outcome proportion or a between-group contrast. The primary group estimates are 67.0% for Lutonix DCB and 49.5% for PTA catheter, but their 95% confidence intervals extend from 50.5% to 79.1% and from 26.2% to 69.2%, respectively. These intervals show that the group proportions are estimated with notable uncertainty. The broader range for the PTA catheter estimate is consistent with its smaller endpoint denominator of 23.0, compared with 49.0 in the Lutonix DCB group.

The primary risk-difference interval, -0.438 to 0.048, is also wide. It includes zero, as well as negative and positive values. Thus, the data do not pin down the magnitude or direction of the underlying difference with precision. The point estimate of -0.195 is one estimate within that uncertainty range, not a value that should be treated as known without error.

Confidence intervals are more informative than a binary interpretation of whether a p-value crosses a threshold because they display both the estimated direction and the range of uncertainty. Even so, the interval is conditional on the statistical method and assumptions used. The registry does not identify the confidence-interval procedure or describe sensitivity analyses. Its precision should not be interpreted as accounting for potential bias from missing follow-up, differences in outcome assessment, or unreported analysis choices.

Precision is distinct from clinical importance. A narrow interval could precisely estimate a small difference, while a wide interval could include both small and substantial differences. The record does not define a minimum clinically important difference for primary patency, so the interval cannot be classified against a registry-reported clinical threshold. The most defensible reading is that the posted primary estimate is uncertain and does not establish a clear group difference.

12. 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 sample-size illustrations describe how many participants per arm would be needed under stated planning assumptions for a future two-group comparison. The figures are not the trial’s original design targets: the registry record does not report the original sample-size justification or the assumptions used to plan enrollment. The illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They calculate planning values using the stated fraction of the observed effect. The values for these binary outcomes are participants per arm, not total events.

The 80% power column represents a planning scenario in which the study is designed to have an 80% chance of detecting an effect of the specified size if that effect is the true one and the assumptions hold. The 90% power column represents a higher planned chance of detection under those same assumptions. Neither percentage describes the probability that the treatment effect is true, nor does it measure the chance that a particular result is correct.

Rows planning for 100%, 75%, and 50% of the observed effect show how the illustrative requirement changes when the assumed effect is smaller than the observed estimate. A smaller effect is harder to distinguish from random variation, so more participants are needed to attain the same planned power and significance level. The observed effect is itself uncertain, especially in this trial’s relatively small endpoint populations; using it as a planning input does not establish that a future study will observe the same effect.

These figures are planning illustrations, not observed power. They should not be read as a retrospective explanation of why the primary comparison was or was not statistically clear. The trial’s actual design assumptions, target power, and sample-size rationale are not reported in the registry record.

13. 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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.673; treatment proportion p₁ = 0.478; average p̄ = 0.576.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6989 = 1.3699.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6852 = 0.5766.
4. n = (1.3699 + 0.5766)² / (-0.1952)² = 99.4, rounded up to 100 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
p0 <- 0.673469387755102                          # control proportion
p1 <- 0.478260869565217                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(2063672)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 100 (80% power), 133 (90% power)
 75% of observed effect: n per arm = 175 (80% power), 234 (90% power)
 50% of observed effect: n per arm = 386 (80% power), 516 (90% power)
power.prop.test: 99.4 
Simulated power at n = 100 per arm: 0.812 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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.

14. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study evaluates several outcomes, time points, treatment comparisons, or subgroups. As the number of statistical tests increases, the chance of obtaining at least one apparently unusual result by chance can increase if each test is interpreted separately. Common approaches include prespecifying a hierarchy of outcomes, adjusting significance thresholds, or clearly labeling secondary analyses as exploratory. The registry record lists 18 secondary outcomes in addition to the primary endpoint, but it does not report a multiplicity strategy. It is therefore not possible to determine whether the secondary comparisons were adjusted, ordered, or intended to support confirmatory claims.

The primary result is reported as an unadjusted comparison. The record does not report whether the primary analysis was prespecified in a protocol or statistical analysis plan, whether other primary analyses were planned, or whether any interim analyses were conducted. Those details are not reported in the registry record; they should not be inferred from the presence or absence of a posted p-value.

The primary endpoint population is participants who completed a 12-month follow-up visit. The posted group denominators differ, and the registry does not explain the reasons for incomplete follow-up or missing endpoint assessments. It also does not report an intention-to-treat analysis, a per-protocol analysis, imputation, or sensitivity analyses for missing outcomes. Without this information, readers cannot assess how much the complete-follow-up definition might affect the comparison or whether conclusions are robust to alternative missing-data assumptions.

The record does not provide enough detail to determine how the randomization sequence was generated, how allocation was concealed, who was masked, or whether outcome assessors remained unaware of assignment. These details can matter for evaluating the risk of bias, especially when outcomes involve clinical decisions such as revascularization. The registry identifies the design as randomized and single-blind, but the operational methods are not reported in the registry record.

Analysis-population definitions also vary by outcome. Primary patency, procedure-time outcomes, and adverse events have different denominators. The registry presents these results, but does not explain all denominator differences or how participants with incomplete assessment were handled for each endpoint. This limits direct cross-outcome comparisons and reinforces the need to interpret each result in its own stated population.

15. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: peripheral artery restenosis (28.3%), intermittent claudication (20.7%), peripheral artery stenosis (13.8%), femoral artery occlusion (10.3%), anaemia (6.9%).

The registry reports adverse-event group counts separately from the primary endpoint population. In the Lutonix DCB group, 44 of 53 participants at risk were recorded as affected by a serious adverse event, 21 of 53 were affected by other adverse events, and 5 deaths were recorded. In the PTA catheter group, 17 of 29 participants at risk were recorded as affected by a serious adverse event, 13 of 29 by other adverse events, and 3 deaths were recorded. These are counts, with their respective group denominators; they are not the primary-patency results.

The most frequently listed serious-event terms include peripheral artery restenosis (28.3%), intermittent claudication (20.7%), peripheral artery stenosis (13.8%), femoral artery occlusion (10.3%), anaemia (6.9%), and cardiac failure congestive (6.9%). The registry record does not provide enough detail in this summary to determine the denominator or event-count basis for each listed percentage, whether events could be counted more than once per participant, or how seriousness and relatedness were adjudicated.

These figures describe events recorded during the trial; they do not by themselves establish that a device caused an event. No statistical comparison of adverse-event rates or causal assessment is reported in the registry record. The groups also differ in the number at risk for these summaries, so raw counts should not be compared without considering the denominators and the study’s safety-analysis methods.

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

The posted data describe primary patency at 12 months among participants who completed that follow-up visit. The proportion was 67.0% in the Lutonix DCB group and 49.5% in the PTA catheter group. The unadjusted risk difference was -0.195 when expressed as PTA catheter minus Lutonix DCB, but its 95% confidence interval included zero. The result therefore presents a numerical difference with substantial uncertainty rather than a clear statistical distinction between the groups.

This finding does not establish equivalence. Equivalence requires a prespecified margin and an analysis designed to test whether the difference lies within that margin; neither is reported in the registry record. Nor does the result show that the groups have identical outcomes. The confidence interval allows a range of possible contrasts, and the available endpoint denominators are limited.

The data also do not establish the timing of restenosis or revascularization, the separate contribution of each primary-endpoint component, or outcomes among participants without a completed 12-month visit. Those details are not reported in the registry record. A fixed-time binary endpoint is useful for comparing the proportion meeting a definition at that time, but it cannot answer every question about durability, clinical course, or later events.

The secondary procedural outcomes offer additional descriptive information, but they address different endpoints and are not a substitute for the primary comparison. Their unadjusted nature and the number of listed secondary outcomes make them less conclusive. Safety counts likewise describe reported events without proving that either intervention caused them.

Overall, the registry results support a cautious statistical reading: the observed group percentages differ, but the primary contrast is imprecise and does not establish a clear between-group difference. The findings should be understood within the registry’s stated follow-up population and its incomplete reporting of the analysis plan, missing data, and endpoint-assessment details. No conclusion about treatment benefit or lack of benefit follows from these results alone.

17. Why This Trial Matters Statistically

This trial illustrates why an observed difference and a statistically clear difference are not the same thing. The primary-patency percentages are separated numerically, yet the confidence interval for the risk difference includes zero and extends across a broad range. A reader who focuses only on the point estimates could overstate certainty; a reader who focuses only on the p-value could overlook the size and uncertainty of the estimated contrast. Considering the estimate, interval, population, and analysis details together gives a more balanced interpretation.

The endpoint also highlights the importance of defining an outcome precisely. Primary patency combines freedom from clinically driven TLR and binary restenosis, so it is a composite status rather than a single event. The registry record does not report the separate component results or the detailed restenosis criterion. Those omissions limit assessment of what primarily determined the overall endpoint.

Differences in denominators matter. The primary comparison uses participants who completed the 12-month visit, while the total enrollment and other outcome populations are different. Without information about missing follow-up, a numerical estimate can be precise only for the analyzed group and method, not automatically for everyone randomized. Transparent reporting of analysis populations and missing-data handling is an essential part of interpreting randomized trials.

Finally, the listed secondary outcomes create a multiplicity question. Several related outcomes can broaden understanding, but unadjusted results across multiple endpoints are more vulnerable to chance patterns. The record’s limited reporting of analysis plans and multiplicity procedures is a useful reminder that statistical findings need context: prespecification, outcome definitions, precision, and the number of analyses all affect how strongly a result should be interpreted.

18. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

Several limitations are specific to the available registry record. First, the primary endpoint is restricted to participants who completed the 12-month follow-up visit, and the record does not explain the smaller and unequal endpoint denominators relative to total enrollment. Reasons for missed visits, incomplete endpoint assessments, and any approach to missing data are not reported in the registry record. The primary estimate may therefore be affected by which participants contributed outcome information.

Second, the record does not give detailed eligibility criteria, the binary restenosis threshold, the procedures used to assess patency, or the method for determining whether TLR was clinically driven. Without these operational details, readers cannot fully evaluate reproducibility or the possibility of differences in outcome assessment. The single-blind designation is not accompanied by a description of who was masked.

Third, the primary comparison is unadjusted, and the registry does not describe the statistical test or confidence-interval method. It does not report the original sample-size justification, the protocol’s analysis plan, or whether interim analyses were conducted. The planning illustrations use the observed effect and stated assumptions, but they do not reveal the study’s original design rationale.

Fourth, the record lists many secondary endpoints, while detailed numerical results and multiplicity handling are limited. This makes it difficult to place individual secondary comparisons in a prespecified inferential framework. The adverse-event summary also lacks detail about event definitions, attribution, repeated events, and the exact basis of listed serious-event percentages.

These reporting limitations do not negate the posted results, but they narrow the conclusions that can be drawn from them. In particular, they constrain assessment of missing-data bias, outcome measurement, robustness to alternative analyses, and the interpretation of secondary and safety findings.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Lutonix® Drug Coated Balloon vs. Standard Balloon Angioplasty for Treatment of Femoropopliteal In-Stent Restenosis — NCT02063672.
• Registry record last updated 2019-04-11; status last verified 2019-03.
• Results first posted 2018-05-23.
• 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.

22. Record Summary

NCT02063672 is a completed, prospective, multicenter, randomized, single-blind, parallel-group trial comparing Lutonix paclitaxel drug-coated balloon angioplasty with standard uncoated balloon angioplasty for femoropopliteal in-stent restenosis. The registry records enrollment of 82 participants and identifies 12-month primary patency as the primary outcome among participants who completed that follow-up.

Primary patency was reported as 67.0% for Lutonix DCB and 49.5% for the PTA catheter group. The unadjusted risk difference, expressed as PTA catheter minus Lutonix DCB, was -0.195 (95% CI -0.438 to 0.048; p = 0.113). The interval includes zero and indicates substantial uncertainty in the comparison. The registry also lists secondary procedural and clinical outcomes and reports adverse-event counts, but does not provide full details of the original statistical plan, missing-data handling, or multiplicity procedures.