TARGET Post-Approval Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for TARGET Post-Approval Study (NCT02800863), a registered phase not stated study. The primary outcome is Rate of Serious Adverse Events (SAEs).

2. Clinical Question

3. Trial Design

TARGET is a prospective, multicenter, single-arm post-approval study sponsored by Abbott Medical Devices. The registry lists the study as completed. Its recorded start date is 2016-08-23 and its primary completion date is 2021-09-23. The registry reports enrollment of 426 patients.

The intervention was DRG stimulation using the Axium or Proclaim Neurostimulator System. The study description focuses on continued safety of these systems. The registry identifies the primary endpoint as the serious adverse event rate for recipients of a permanent implantable pulse generator, assessed throughout the 12-month study period. The primary analysis population is described as 296 people who received a permanent implant. That is a narrower population than the enrolled group, and the record does not give a detailed account of the reasons people did not enter the permanent-implant analysis.

This design can describe outcomes among those treated and included in the analysis, but it does not provide a randomized, like-for-like control comparison. Allocation is not stated in the registry record, and no comparator arm is described. The findings therefore cannot isolate how outcomes would have differed under another treatment or without DRG stimulation.

The registry lists three secondary outcomes: change in overall pain intensity measured by the Visual Analog Scale, change in physical function measured by the PROMIS-29 Physical Function Scale, and change in quality of life measured by the PROMIS Global Health Scale. Each is described as a baseline-to-12-month outcome after permanent implantation. The record names these measures but does not report their numerical results or analysis 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:

Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed includes subjects who were available at that time of analysis.

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 Rate of Serious Adverse Events (SAEs), measured over throughout 12 month study.

The primary endpoint is the serious adverse event rate for people who received a permanent DRG implantable pulse generator, assessed throughout the 12-month study period. The registry labels its unit as a percentage of events and states that the rate was analyzed using the Kaplan-Meier method. The primary population is 296 permanent-implant recipients; the registry also notes that the number analyzed includes participants available at the time of analysis.

Safety endpoints are used to describe the occurrence of serious harms during follow-up. A time-to-event approach can be useful when participants have different lengths of observed follow-up or when some are no longer observed before the study period ends. In general, Kaplan-Meier methods estimate event experience over time while accounting for incomplete follow-up through censoring. The registry record does not provide details about censoring rules or the operational definition of a serious adverse event.

A rate expressed as a percentage of events is not automatically the same quantity as the proportion of participants who experienced an event. The exact interpretation depends on the analysis definition. Although the registry describes the planned analysis and population, it does not report the primary endpoint estimate, standard error, or confidence interval. The precision and magnitude of the primary safety result therefore cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the Kaplan-Meier method estimate?

Kaplan-Meier is a time-to-event method. In general, it estimates how event experience accumulates over follow-up while retaining information from participants whose observation ends before the study period is complete. Such participants may be censored: their follow-up contributes up to the last time they are known to be observed, without being treated as if an event occurred at that time. The registry states that this method was used for the serious adverse event rate among permanent-implant recipients. It does not report the censoring rules, event-time details, or the exact form of the estimate.

Time-to-event methods are relevant when the timing of an event matters or follow-up duration differs. They are not equivalent to simply dividing a count by a group size. A Kaplan-Meier estimate depends on the event and censoring information over follow-up. Because the registry does not post that information or the resulting estimate, the reported method alone cannot establish the rate or its precision.

What does the standard error describe?

A standard error describes the sampling variability of an estimate under a statistical model. In general, a smaller standard error indicates greater precision, while a larger one indicates more uncertainty. The primary endpoint lists standard error as its dispersion measure, but no standard error result is reported in the registry record. Without the estimate and its standard error, readers cannot judge how much uncertainty surrounds the primary result.

A confidence interval is often used to express uncertainty around an estimate in a way that shows a range of plausible values under the model. No interval is reported for the primary endpoint. The absence of an interval does not mean the result is precise or imprecise; it means that its precision cannot be evaluated from the posted results.

How should the analysis population be understood?

The registry reports enrollment of 426 and identifies 296 recipients of a permanent implant as the primary analysis population. The primary description also says that the number analyzed includes participants available at the time of analysis. These statements indicate that the analysis population is defined by implant receipt and availability for analysis, rather than simply by enrollment. The registry record does not provide a participant flow, reasons for non-inclusion, or the number contributing data at each follow-up point.

In general, analysis populations matter because results depend on who is included and what information is available. A group defined by receipt of an implant may differ from everyone enrolled, and incomplete follow-up may affect the information used by a time-to-event analysis. The registry record does not give enough detail to assess the direction or size of any such effects.

What can a single-arm design establish?

A single-arm study observes outcomes in a treated group without a concurrent control group. It can describe events and outcomes in that group, but it cannot directly estimate a treatment contrast against an alternative. Differences from baseline, if reported, would also require cautious interpretation because changes over time can reflect factors other than the intervention. The registry describes no randomized comparison, and allocation is not stated.

For this study, the stated objective is continued safety evaluation rather than a reported comparison between groups. The absence of a control group does not make descriptive safety information meaningless, but it limits attribution and comparative interpretation. Any claim about how the observed event experience differs from another treatment would require evidence not reported in the registry record.

What do the outcome descriptions and analyses show?

The registry names a primary safety endpoint and secondary measures of pain intensity, physical function, and quality of life. The secondary outcomes are described as changes from baseline to 12 months after permanent implantation. The record lists 4 outcome measures and 0 analyses, but provides no numerical outcome estimates, standard errors, or confidence intervals for these measures. An outcome being named in a registry is not the same as a result being reported.

In general, an outcome estimate needs context: the scale or unit, the analysis population, the amount of available follow-up, and a measure of uncertainty. For continuous outcomes, a mean change describes an average change on the stated measure, while the spread of individual changes can be different from the uncertainty in that average. The registry identifies the primary measure as continuous in its statistical categorization, but the endpoint itself is a serious adverse event rate analyzed over time. No numerical mean or dispersion result is posted that would support interpretation of a continuous endpoint.

How should planning calculations be read?

In general, sample-size planning calculations describe how many participants might be needed under stated assumptions to detect a chosen effect with a specified power and significance level. They are planning illustrations, not observed outcomes and not evidence that a study achieved a particular probability of detecting an effect. The registry's planning description refers to two-sided significance level 0.05, equal allocation between two arms, and a normal approximation, with the effect set as a fraction of an observed effect. It also distinguishes time-to-event calculations, which give a total number of events, from other calculations, which give participants per arm.

Those assumptions do not turn this single-arm study into a two-arm comparison. The registry record does not report numerical planning results, and the primary endpoint estimate needed to describe an observed effect is not posted. Any planning illustration should therefore be kept separate from the observed safety counts and from evidence about the study's actual design or findings.

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("Dorsal Root Ganglion (DRG) Stimulation")
n   <- c(296)
m   <- c(8.7)
sp  <- c(1.7)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Dorsal Root Ganglion (DRG) Stimulation  296  8.700  29.248  5.354  12.046

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures: the primary serious adverse event endpoint and secondary outcomes for pain intensity, physical function, and quality of life. It records 0 analyses. The record does not report a multiplicity adjustment or explain how the chance of false-positive findings across multiple outcomes was handled. Because numerical results for the secondary outcomes are not reported, it is not possible to assess their estimates or how any multiplicity approach might affect their interpretation.

The primary analysis description says that participants available at the time of analysis were included. It identifies 296 permanent-implant recipients as the primary population, compared with enrollment of 426. The registry does not provide the number contributing data at each follow-up point, reasons for missing observations, or the approach used to handle missing data. It also does not report whether sensitivity analyses were performed.

These omissions matter because availability of follow-up can shape the analyzed data, and the assumptions used to handle incomplete observations can affect estimates. For a time-to-event analysis, censoring rules and follow-up information are particularly relevant. They are not reported in the registry record. The record therefore supports identification of the stated population and method, but not an assessment of missing-data assumptions, robustness, or multiplicity control.

12. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia (1.2%), death (0.7%), embolism (0.5%), gastrointestinal or genitourinary compromise (0.5%), cellulitis (0.2%).

The adverse-event listing for the DRG stimulation group reports 426 at risk for serious adverse events and 26 under the serious-event count. It reports 426 at risk for other adverse events and 5 under that count, and lists 3 deaths. These entries are descriptive counts as recorded; they are not the primary Kaplan-Meier estimate, which concerns the permanent-implant population of 296. The registry record does not explain how the adverse-event listings relate to that primary population or whether counts represent events, affected participants, or both.

The listed serious-event terms and percentages are Pneumonia, 1.2%; Death, 0.7%; Embolism, 0.5%; Gastrointestinal or Genitourinary Compromise, 0.5%; Cellulitis, 0.2%; and Acute Community Acquired Pneumonia, 0.2%. The record does not specify the denominator or whether event categories can overlap, so these percentages should not be combined or interpreted as a complete distribution.

Without a control group, these figures do not establish comparative risk. Without event timing, follow-up detail, and the primary endpoint estimate, they also cannot substitute for the stated 12-month safety analysis.

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

The registry record establishes that TARGET was a prospective, multicenter, single-arm post-approval study of DRG stimulation using the Axium and Proclaim Neurostimulator Systems. It describes a primary safety endpoint based on serious adverse events through the 12-month study period and identifies 296 permanent-implant recipients as the primary population. The record also contains descriptive adverse-event counts and lists serious-event terms with percentages.

However, the primary endpoint result itself is not reported. There is no posted serious adverse event rate, standard error, or confidence interval. The registry also does not report numerical results for the secondary outcomes of pain intensity, physical function, or quality of life. Thus, the posted results do not allow readers to assess the magnitude or precision of the primary safety estimate or the secondary outcome changes.

The design also limits interpretation. Because the study is single arm and has no concurrent comparator, the event counts cannot quantify how outcomes would have differed under another intervention. They do not establish a causal treatment effect. The registry record does not report allocation details, missing-data methods, or the censoring rules used for the time-to-event analysis.

In general, a registry description of methods and adverse-event listings can help clarify what investigators intended to assess and what types of events were recorded. It is not a replacement for complete outcome estimates and analysis details. The counts and percentages should be read as reported descriptive information, not as proof of comparative safety or as a complete account of each participant's experience.

Planning calculations, when available, answer a different question from observed results: they illustrate sample sizes under assumptions rather than describing what happened in the study. The registry record does not report numerical planning results. Nothing in the available record supports interpreting planning assumptions as observed power or as evidence that an endpoint was met.

14. Why This Trial Matters Statistically

Post-approval studies address safety experience after a device has entered clinical use. TARGET's registry record is statistically notable for distinguishing enrollment from the group used for the primary analysis: 426 patients were enrolled, while the primary population is described as 296 recipients of a permanent implant. Keeping those populations separate is essential when interpreting who contributes to a safety estimate.

The study also illustrates why the name of an endpoint and its analysis method are not enough to evaluate a result. The registry identifies a 12-month serious adverse event rate and says it was analyzed using Kaplan-Meier methods, but does not report the estimate or its uncertainty. Without these, readers cannot assess the endpoint's magnitude or precision. The descriptive adverse-event listings provide additional context, but they do not replace the stated primary analysis.

The single-arm design is another important statistical feature. It can describe recorded events among the treated group, but it does not provide a controlled estimate of differences from another treatment. Registry readers should distinguish description from comparison, and method descriptions from posted findings.

Finally, the record names patient-centered outcomes involving pain, physical function, and quality of life, but does not report their numerical results. This gap matters because a complete interpretation requires both safety information and the outcome estimates the registry identifies as secondary measures. The record therefore offers useful design and population details while leaving key statistical results unavailable.

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 main limitation for interpreting this specific record is that the stated primary endpoint result is absent. Although the registry identifies the Kaplan-Meier method, the permanent-implant population, and the follow-up period, it does not report the estimated serious adverse event rate, its standard error, or a confidence interval. The precision and magnitude of the primary result are therefore unknown from the registry record.

The enrolled population and primary analysis population differ: enrollment is 426 and the permanent-implant analysis population is 296. The record does not explain the path between these populations, give reasons for non-inclusion, or report the number available at each analysis time. It says that analysis includes participants available at the time, but does not describe missing-data handling or sensitivity analyses.

The serious and other adverse-event counts and listed terms are not accompanied by event timing, detailed definitions, or a clear explanation of how the entries relate to the primary analysis population. The record also does not specify the denominators for the listed term percentages or whether event categories overlap. These limitations make it inappropriate to treat the listings as a substitute for the primary time-to-event estimate.

The single-arm design has no concurrent comparator, and allocation is not stated. Consequently, the record cannot provide a direct comparative estimate. Although the registry names secondary outcomes for pain, physical function, and quality of life, it does not report their numerical results or analysis details. Multiplicity handling and the statistical plan are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: TARGET Post-Approval Study — NCT02800863.
• Registry record last updated 2024-07-08; status last verified 2024-01.
• Results first posted 2024-07-08.
• 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

TARGET is a completed, prospective, multicenter, single-arm post-approval study sponsored by Abbott Medical Devices. It evaluated Axium and Proclaim systems for DRG stimulation in people with chronic, intractable lower-limb pain due to CRPS types I and II. The registry reports enrollment of 426 and identifies 296 permanent-implant recipients as the primary analysis population.

The primary endpoint was the serious adverse event rate through the 12-month study period, analyzed using Kaplan-Meier methods. The registry record does not report the estimated rate or its uncertainty. It lists adverse-event counts and serious-event terms, but does not provide the details needed to connect those listings to the primary analysis. Numerical results for the named secondary outcomes are also not reported.