This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Study Evaluating the Safety and Efficacy of a Once-daily Dose of Tigecycline vs Ertapenem in Diabetic Foot Infections (DFI) With a Substudy in Patients With Diabetic Foot Infections Complicated by Osteomyelitis. (NCT00366249), a randomized phase 3 study. The primary outcome is Number of Patients With Clinical Response of Cure Vs. Failure..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00366249 |
| Phase | Phase 3 |
| Condition | Bacterial Infections, Diabetic Foot, Osteomyelitis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 1061 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Wyeth is now a wholly owned subsidiary of Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
The primary endpoint concerns the clinically evaluable population without osteomyelitis. The broader trial studied subjects with diabetes and foot infections; the registry title also identifies a substudy in patients whose diabetic foot infections were complicated by osteomyelitis. The number of participants in each analysis population is not reported in the registry record.
Intervention
The intervention was tigecycline, described in the title as a once-daily dose. The registry record does not state the dose amount or provide further details about treatment administration in the arm description.
Comparator
The comparator was ertapenem. The trial was randomized, double-blind, and parallel-group, with triple masking recorded. The arm descriptions do not add details about the treatment regimens.
Primary question
The primary endpoint asks how many patients had a clinical response classified as cure rather than failure at the test-of-cure visit, assessed at least 12 days after the last dose. The registry summary states that the co-primary efficacy endpoints were not met. Numerical response results, an effect estimate, and its precision are not reported in the registry record.
3. Trial Design
This was a randomized, double-blind, parallel-group Phase 3 study comparing tigecycline with ertapenem for foot infections in subjects with diabetes. The official title describes it as multicenter. The registry records triple masking and an enrollment of 1061. The study status is completed; the recorded start was 2007-01 and primary completion was 2009-03.
The broad study focus was safety and efficacy in diabetic foot infections. The record also identifies a substudy involving patients whose infections were complicated by osteomyelitis. The primary endpoint population is described more narrowly as clinically evaluable patients without osteomyelitis. How the clinically evaluable population was defined, and how patients were assigned to that population, are not reported in the registry record.
The listed primary measure is the number of patients with clinical response of cure versus failure at the test-of-cure visit, assessed at least 12 days after the last dose. The record describes co-primary efficacy endpoints, but does not provide their complete definitions or numerical results. It states that these endpoints were not met. Secondary outcomes include clinical response assessed at least 25 - 27 weeks after the last dose, with cure versus failure and cure versus failure/indeterminate classifications, and microbiologic response of eradication.
The record identifies five outcome measures and three analyses, but does not give enough detail to reconstruct the analysis sequence or the planned statistical procedures. Allocation concealment, the randomization method, treatment duration, arm-specific enrollment, and the statistical analysis plan 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.
Before assignment: Patients were screened for up to 24 hours.
Overall Study
| Stage | Tigecycline | Ertapenem |
|---|---|---|
| STARTED | 553 | 508 |
| COMPLETED | 422 | 430 |
| NOT COMPLETED | 131 | 78 |
Reasons for not completing this period:
| Reason | Tigecycline | Ertapenem |
|---|---|---|
| Adverse Event | 53 | 28 |
| Death | 0 | 1 |
| Physician Decision | 5 | 2 |
| Lost to Follow-up | 2 | 0 |
| Protocol Violation | 1 | 2 |
| Withdrawal by Subject | 18 | 4 |
| Lack of Efficacy | 21 | 21 |
| Most due to osteomylitis status | 31 | 20 |
Analysis population for the primary outcome, as defined in the registry: Clinically evaluable population without osteomyelitis.
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.
| Characteristic | Unit | Tigecycline | Ertapenem | Total |
|---|---|---|---|---|
| Participants analysed | 553 | 508 | 1061 | |
| Age Continuous | years | 59.36 (SD 12.04) | 58.75 (SD 11.70) | 59.07 (SD 11.88) |
| Sex: Female, Male: Female | Participants | 199 | 165 | 364 |
| Sex: Female, Male: Male | Participants | 354 | 343 | 697 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Patients With Clinical Response of Cure Vs. Failure., measured over Test of cure visit (TOC): Assessed at least 12 days post last dose.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | patients |
| Endpoint classification | Binary Endpoint |
The primary endpoint classifies a patient’s clinical response as cure or failure. The registry defines cure as recovery without added antibiotic therapy. Failure includes added antibiotic therapy for no response or worsening after improvement, new purulence, more than 120% doses, non-routine surgical treatment, or death related to diabetic foot infection more than 48 hours after treatment. The test-of-cure assessment was scheduled at least 12 days after the last dose.
A clinical endpoint can capture whether the infection met a prespecified response definition, rather than measuring only a laboratory finding. Here, the classification also includes events related to additional treatment, worsening, surgery, and infection-related death. Such a composite definition can be useful for summarizing different ways a treatment course may be judged unsuccessful, but its interpretation depends on the exact criteria and consistent application across groups.
The endpoint is reported for the clinically evaluable population without osteomyelitis. The registry record does not explain the criteria for clinical evaluability or report the number of patients included in that population. It also does not give the arm-specific counts, response proportions, treatment contrast, or confidence interval for this endpoint. Therefore, the endpoint definition is available, but its magnitude and statistical precision cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry summary reports that the co-primary efficacy endpoints were not met. This is the central efficacy statement available in the record. It is not accompanied by arm-specific clinical response counts, an estimated difference between treatments, a confidence interval, or a p-value. The size and precision of any observed contrast are therefore not reported in the registry record, and the statement alone does not show how close the results were to any criterion.
The listed primary measure is a clinical cure-versus-failure classification at test of cure. Its definitions combine clinical course and subsequent care, including added antibiotic therapy, worsening, new purulence, non-routine surgical treatment, and infection-related death. The endpoint applies to clinically evaluable patients without osteomyelitis. That population restriction matters when interpreting the result: the record does not establish that this endpoint estimate represents the osteomyelitis substudy or every participant enrolled in the broader trial.
The record separately lists longer-term clinical response assessments and a microbiologic eradication outcome. Their presence does not establish what those outcomes showed. No numerical results for them are reported in the registry record. The brief summary’s statement about co-primary efficacy endpoints should not be extended to every secondary outcome or to the safety outcomes without their corresponding results.
The adverse-event information lists 79 serious events in the tigecycline group and 62 in the ertapenem group, and 406 other events and 292 other events, respectively. The registry record does not report the corresponding numbers at risk for these summaries. Without denominators and a fuller definition of the event-counting approach, these counts alone do not give comparative event rates. The listed serious terms and percentages describe entries in the record, but do not provide a complete group-level safety comparison.
Failure to meet co-primary efficacy endpoints is not evidence that the treatments have identical effects. Establishing the direction and precision of a treatment contrast requires the outcome estimates and their uncertainty, neither of which is available for the primary endpoint in the registry record. The finding also cannot, by itself, establish the result for patient groups outside the stated analysis population or answer questions about outcomes not reported in the record.
9. Statistical Methods Explained
Randomization is a design method intended to make treatment groups comparable, on average, with respect to measured and unmeasured factors at the start of a trial. It does not guarantee that groups will be identical, and it cannot replace reporting the methods used to generate and implement assignments. The record identifies the study as randomized but does not report the randomization sequence method, allocation concealment, or any stratification factors.
Blinding is intended to reduce the influence of treatment knowledge on care, outcome assessment, or reporting. This trial is recorded as double-blind and triple-masked. The registry record does not specify which roles were masked, how masking was maintained, or whether it was assessed. The parallel-group description indicates that participants were assigned to treatment groups followed over the trial rather than crossing between treatments; detailed treatment schedules are not reported.
What does a cure-versus-failure endpoint measure?
A binary outcome places each assessed patient into a defined category, such as cure or failure. The endpoint’s clinical definition determines which events count as failure and which patients qualify for assessment. A count of patients in a category is not, by itself, a rate or a comparison: interpreting it requires the relevant denominator and analysis population. The registry lists the endpoint as a number of patients and specifies the clinically evaluable population without osteomyelitis, but does not report the group-specific outcome counts or denominators.
In a comparative trial, an effect estimate expresses how outcomes differ between treatment groups using a chosen scale. A confidence interval describes the statistical uncertainty around an estimate under the assumptions of the analysis. A narrow interval generally indicates greater precision than a wide interval, while an interval compatible with materially different effects signals uncertainty. These are general explanations; the registry record does not report a primary effect estimate or confidence interval for this comparison.
Why do the analysis population and endpoint definition matter?
Analysis populations specify which randomized participants contribute to a particular result. An evaluable-population analysis may exclude participants who do not meet the specified assessment criteria, so its interpretation depends on those criteria and on how exclusions were handled. The label “clinically evaluable” is reported, but the operational definition, exclusions, and handling of missing endpoint assessments are not reported in the registry record. It is therefore not possible to judge from the record whether the analysis preserved the comparability created by randomization.
The endpoint definition also includes decisions about additional antibiotics, worsening, new purulence, surgery, and infection-related death. When an outcome combines multiple components, the overall classification may reflect any qualifying component. The registry gives the categories but does not report how often each component occurred or how endpoint assessments were adjudicated. Those details would help distinguish the clinical pathways contributing to the overall response classification.
What can be inferred from the statistical summary?
The registry’s brief summary states that the co-primary efficacy endpoints were not met. A threshold-based conclusion does not reveal the exact observed effect, its precision, or whether the result reflects a small estimated difference, substantial uncertainty, or another feature of the analysis. The underlying statistical plan, test, significance threshold for the efficacy analysis, confidence intervals, and handling of multiple co-primary endpoints are not reported in the registry record. No specific test or model should be attributed to the trial from the available information.
The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. These are planning illustrations, not observed power, and they are not a substitute for the trial’s own design justification. The registry record does not report the original sample-size rationale or whether the trial used other assumptions or procedures.
Over-dispersion is a general issue that arises when outcome variability is greater than a model assumes; if ignored, standard errors can be too small and uncertainty can be understated. It is not possible to determine whether over-dispersion applies to this endpoint or whether any model addressed it, because the endpoint results and statistical methods are not reported in the registry record. Likewise, no recalculated treatment contrast can be made from the posted primary-outcome information.
10. Multiplicity, Missing Data and Analysis Populations
The record describes co-primary efficacy endpoints, but does not report their complete definitions, testing sequence, or the procedure used to control the chance of a false-positive finding across multiple outcomes. The brief summary says the co-primary efficacy endpoints were not met. Without the prespecified multiplicity approach and endpoint-level numerical results, the statistical interpretation of that statement cannot be reconstructed in detail.
Several secondary outcomes are listed, including late clinical response classifications and microbiologic eradication. The registry record does not report their numerical results or explain whether they were adjusted for multiple comparisons. A result on a secondary outcome, if available elsewhere, would need to be interpreted in light of its prespecification and the multiplicity strategy; those details are not reported in the registry record.
The primary endpoint is defined for clinically evaluable patients without osteomyelitis. The record does not provide the evaluability criteria, the number excluded from that population, the extent or reasons for missing outcome data, or the method used to handle missing assessments. It also does not report whether analyses were conducted in other populations, such as all randomized participants, or how results across populations were compared.
These omissions limit assessment of potential selection effects and robustness. If availability of an endpoint assessment is related to treatment or outcome, an analysis restricted to evaluable participants can differ from an analysis that retains all randomized participants. This is a general methodological concern, not a claim that such bias occurred in this trial. The registry record does not give the information needed to evaluate it.
11. What the Result Does, and Does Not, Mean
The registry record supports a limited conclusion: the trial’s brief summary states that the co-primary efficacy endpoints were not met. It identifies the primary clinical response definition and its assessment time, but does not provide the arm-level results or a treatment-effect estimate. Readers therefore cannot quantify the observed difference or judge its statistical precision from the registry record.
Not meeting a co-primary endpoint does not establish that the treatments have the same effect. A statistical result may be uncertain, and the direction and possible range of effects require an estimate and an uncertainty measure. Neither is reported for the primary clinical response comparison. The result also does not establish that either treatment is superior or inferior on unreported secondary outcomes, or that the same conclusion applies to the osteomyelitis substudy.
The endpoint classifies outcomes according to the registry’s criteria and is limited to a clinically evaluable population without osteomyelitis. The record does not explain how that population was formed or how missing assessments were handled. Conclusions should therefore remain tied to the stated endpoint and analysis population, rather than being generalized to all participants or all clinical circumstances.
The safety summary lists event counts but does not report the corresponding numbers at risk for these group summaries. Counts without denominators are insufficient for comparing incidence between treatment groups. The listed serious-event terms and percentages do not provide a complete safety profile, and should not be treated as a full account of all possible harms.
These results are a statistical description of what the registry summary reports, not individualized guidance. They do not determine what treatment is appropriate for a particular patient. The information needed for a fuller comparison—including detailed efficacy estimates, uncertainty, analysis methods, missing-data handling, and complete safety denominators—is not reported in the registry record.
12. Why This Trial Matters Statistically
This trial illustrates why a registry conclusion and a numerical treatment comparison are not interchangeable. The brief summary reports that the co-primary efficacy endpoints were not met, but does not report the primary endpoint counts, effect estimate, confidence interval, or p-value. Without those quantities, readers cannot evaluate the size or precision of the observed contrast or see how the endpoint result relates to its clinical definition.
It also highlights the importance of analysis populations. The primary measure is described for clinically evaluable patients without osteomyelitis, while the study title identifies a substudy involving osteomyelitis. The record does not define clinical evaluability or give population-specific results. A population label is not enough to assess who contributed to the analysis, whether exclusions differed across groups, or how well conclusions apply beyond that population.
The endpoint combines several clinical criteria, including subsequent antibiotic treatment and other indicators of failure. Reporting component-level outcomes could clarify what drove the overall classification, but those results are not reported in the registry record. Likewise, listing secondary outcomes does not communicate their findings or their relationship to the primary analysis.
Finally, the safety summaries show why event counts need context. The record gives group counts and selected serious-event terms, but not the numbers at risk for the summaries. Statistical interpretation depends on denominators, outcome definitions, and uncertainty, not counts alone. This record is therefore a useful example of how trial design details can be available while key information needed to independently assess efficacy and safety remains unreported.
13. 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 principal limitation for interpreting this trial from the registry record is the absence of numerical primary efficacy results. The record states that the co-primary efficacy endpoints were not met, but does not provide response counts by group, denominators, an effect estimate, a confidence interval, or a p-value. The magnitude and precision of the treatment comparison cannot be evaluated.
Details needed to assess the analysis are also missing. The registry record does not define the clinically evaluable population, describe the randomization procedure or allocation concealment, identify the masked roles, or provide the statistical analysis plan. The handling of missing data, exclusions, protocol deviations, and multiplicity across co-primary and secondary endpoints is not reported. These gaps prevent an independent assessment of how the reported conclusion was reached.
The registry identifies an osteomyelitis substudy but does not give its population size or results. The primary endpoint population is specified as clinically evaluable patients without osteomyelitis, so the primary endpoint description cannot be assumed to cover that substudy. The listed longer-term clinical and microbiologic outcomes also lack numerical results in the registry record.
Safety interpretation is limited by the absence of denominators for the event-count summaries and by the lack of a complete account of definitions and analysis methods. The listed event terms are not sufficient to reconstruct comparative risks. These are limitations of the information reported in the registry record; they do not establish that the underlying trial lacked these analyses or data.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Study Evaluating the Safety and Efficacy of a Once-daily Dose of Tigecycline vs Ertapenem in Diabetic Foot Infections (DFI) With a Substudy in Patients With Diabetic Foot Infections Complicated by Osteomyelitis. — NCT00366249.
- Registry record last updated 2010-04-28; status last verified 2010-04.
- Results first posted 2009-08-21.
- 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.
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17. Record Summary
The registry describes a completed, randomized, double-blind, parallel-group Phase 3 study comparing once-daily tigecycline with ertapenem for diabetic foot infections. It records triple masking, enrollment of 1061, a start date of 2007-01, and primary completion in 2009-03. The official title describes the study as multicenter and identifies an osteomyelitis substudy.
The primary measure is clinical cure versus failure at test of cure, assessed at least 12 days after the last dose, in the clinically evaluable population without osteomyelitis. The registry summary states that the co-primary efficacy endpoints were not met. Numerical efficacy results, treatment-effect estimates, and their precision are not reported in the registry record. Secondary outcomes include later clinical response and microbiologic eradication, but their results are also not reported. Safety summaries include event counts and selected serious-event terms, without the numbers at risk for those summaries.