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 Pharmacokinetics of Daptomycin During Cardiopulmonary Bypass Surgery (NCT00701636), a non-randomized phase 3 study. The primary outcome is Mean Daptomycin Concentrations at 12, 18, 24, and 48 h.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00701636 |
| Phase | Phase 3 |
| Condition | Late Effects of Surgery, Staphylococcus Aureus, Surgical Site Infection |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 30 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing coronary artery bypass graft surgery without valvular replacement. The registry lists enrollment of 30 participants.
Intervention
Daptomycin used as surgical antibiotic prophylaxis. The case-group description says the first 15 subjects enrolled would receive daptomycin.
Comparator
A standard-of-care antibiotic group intended as a reference for the cases. The control-group description says 15 subjects would receive no experimental medications or treatments; further details of the standard-of-care regimen are not reported in the registry record.
Primary question
What are the mean daptomycin concentrations at 12, 18, 24, and 48 h in patients undergoing this surgery? The registry names these measurements but does not report their values or a comparison of concentrations between groups.
The clinical question is primarily pharmacokinetic: it concerns measured drug concentrations over time in the surgical setting. The registry also describes a reference group and reports serious adverse-event counts, but the study is not recorded as randomized. The groups therefore should not be read as a randomized treatment comparison. The registry's stated outcome timeframe is hospital discharge or 7 days, whichever comes first; it does not explain how that timeframe relates to collection of the measurements at the specified hours.
3. Trial Design
The registry identifies this as a prospective, open-label pharmacokinetic study of daptomycin prophylaxis during coronary artery bypass graft surgery without valvular replacement. It lists Phase 3, non-randomized allocation, no masking, and a single-group model. The arm descriptions nevertheless name cases receiving daptomycin and controls receiving standard-of-care antibiotics. These descriptions make clear that a reference group was planned, but the registry's model and allocation fields do not describe a randomized two-group design.
The record lists enrollment of 30. Its case-group description says the first 15 subjects enrolled would receive daptomycin; the control-group description says 15 subjects would be enrolled in the standard-of-care antibiotic group. The intended purpose of controls was to provide a reference for intervention patients. Because assignment was not randomized, differences between groups may reflect factors other than the intervention. The registry itself cautions that the arms are not a like-for-like control comparison.
The study is listed as completed. Its start is recorded as 2008-07 and its primary completion as 2010-10. The sponsor is the Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center. The registry does not report further details about recruitment, adherence, the control regimen, or how the two groups were made comparable.
The design is useful to describe as a pharmacokinetic investigation rather than as a randomized efficacy trial. Its primary endpoint concerns daptomycin concentrations, while the control group is described as a reference. The registry does not report a protocol-level account of how concentration comparisons were planned or analyzed.
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
| Stage | Cases | Controls |
|---|---|---|
| STARTED | 15 | 15 |
| COMPLETED | 15 | 15 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Based on sample sizes from previously published studies on antibiotic pk for CABG surgery.
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: Our protocol says we will enroll 32 subjects, with the assumption that 2 may not finish the study, have protocol violations, or have data that is corrupt and unusable. Our target was 30 analyzable subjects. Since we had no subjects withdraw from the trial, and no protocol violations or data problems, we halted enrollment at 30 subjects.
| Characteristic | Unit | Cases | Controls | Total |
|---|---|---|---|---|
| Participants analysed | 15 | 15 | 30 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 12 | 12 | 24 |
| Age, Categorical: >=65 years | Participants | 3 | 3 | 6 |
| Age, Continuous | years | 56 (SD 8.0) | 57 (SD 8.7) | 56 (SD 7.4) |
| Sex: Female, Male: Female | Participants | 3 | 2 | 5 |
| Sex: Female, Male: Male | Participants | 12 | 13 | 25 |
| Region of Enrollment: United States | participants | 15 | 15 | 30 |
6. Primary Endpoint
The registry lists the primary outcome as Mean Daptomycin Concentrations at 12, 18, 24, and 48 h, measured over Hospital discharge or 7 days, whichever comes first.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | mcg/ml |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the mean daptomycin concentration, measured in mcg/ml at 12, 18, 24, and 48 h. Concentration is a continuous measure: it records an amount on a scale rather than classifying participants into outcome categories. The registry specifies standard deviation as the dispersion measure, which would describe how spread out observed concentrations are around their mean.
Pharmacokinetic concentration measurements are used to characterize the presence of a drug in the body over time. In general, measurements at multiple time points can describe how concentrations vary during the observation period. They do not, by themselves, establish a clinical benefit or show that a regimen prevents infection.
The listed outcome timeframe is hospital discharge or 7 days, whichever comes first. How that timeframe applies to the measurements at 12, 18, 24, and 48 h is not explained in the registry record. Although the endpoint title and description specify the concentration measurements, the registry does not report the observed means, standard deviations, participant counts contributing at each time point, or any estimated differences between groups. As a result, the endpoint is identifiable, but its measured results cannot be interpreted from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies the intended primary measure clearly: mean daptomycin concentration at 12, 18, 24, and 48 h, with standard deviation as the stated measure of dispersion. However, it does not report the observed concentrations. There are no posted primary endpoint estimates in the record summarized by these registry entries, and no analyses are listed. Consequently, the record does not support a conclusion about the concentration levels, their variability, or how they differ between cases and controls.
The study is non-randomized and open-label. Its case and control descriptions indicate different antibiotic approaches, but the registry cautions that the arms are not a like-for-like control comparison. In general, non-randomized group comparisons can be influenced by differences in participant characteristics, care, or other factors. Without reported adjustment methods and participant-level or summary results, the direction or magnitude of such influences cannot be assessed.
The serious adverse-event counts are separate from the missing concentration results. The registry lists 0 serious events among 15 cases and 3 among 15 controls. It identifies surgical site infection as the top serious term at 20.0%. These counts describe what is recorded for the groups; they do not establish that the intervention caused or prevented events. The non-randomized design, absence of a reported analysis, and lack of further safety detail limit comparative interpretation. Death counts are not reported in the registry record.
The distinction between a stated endpoint and a reported result matters. A registry may specify what investigators intend to measure without posting the measurements or the analysis. Here, the endpoint definition gives the reader a clear sense of the study's focus, but not the empirical findings needed to quantify concentrations or evaluate uncertainty. Confidence intervals, hypothesis tests, adjusted comparisons, and statistical conclusions for the primary endpoint are not reported in the registry record.
The record lists enrollment of 30 and describes 15 cases and 15 controls. These group descriptions explain the intended structure but do not supply the number with usable concentration data at each time point. The registry also does not state whether every participant contributed all planned measurements. Thus, even the denominator for a concentration estimate at a particular time cannot be determined from the record.
Any planning illustration based on an observed effect should not be read as evidence of achieved power or as a substitute for the missing outcome estimates. In general, sample-size planning illustrates what a design might detect under stated assumptions; it does not establish the precision or significance of results after data collection. The registry record does not provide the primary concentration results needed to ground such an interpretation.
9. Statistical Methods Explained
The registered endpoint is a continuous outcome: mean concentration in mcg/ml at specified times. For a continuous measure, a mean describes the central level of observed values, while a standard deviation describes their spread. These summaries answer different questions. The mean indicates the average concentration in the analyzed observations; the standard deviation indicates how much individual observations vary around that average. Neither quantity is reported for the primary endpoint in the registry record.
What would a confidence interval describe?
In general, a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the statistical method. For a mean concentration, it would help show how precisely that mean was estimated. For a difference between groups, it would describe uncertainty in the estimated contrast. A narrow interval indicates greater precision than a wide interval, but an interval cannot be interpreted without knowing the estimate, the analysis population, and the method used. No confidence intervals or primary endpoint estimates are reported in the registry record.
Why does the study design matter?
The record identifies the allocation as non-randomized and says there was no masking. Random assignment is a method intended to balance participant characteristics across groups on average; it is not recorded for this study. In a non-randomized comparison, groups may differ for reasons related to how participants entered or received care. Statistical adjustment can sometimes address measured differences, but it cannot automatically remove unmeasured differences. The registry does not report an adjustment plan or adjusted concentration results. Open-label status means that masking was not used, but the record does not explain whether awareness of treatment could have affected measurement or clinical decisions.
The registry describes a single-group model while also naming cases and controls. It says the controls were intended as a reference group, and it cautions that the arms are not a like-for-like control comparison. This makes it important to distinguish descriptive pharmacokinetic estimates from a causal comparison. Reporting average concentrations in the daptomycin group would describe that group; a contrast with controls would require an explicit analysis and careful interpretation of the non-randomized design.
How should the time points be understood?
In general, repeated measurements over time can help characterize how a continuous outcome changes or varies during follow-up. Measurements from the same participant may be related, so an analysis of multiple time points may need to account for that correlation. The registry lists concentrations at 12, 18, 24, and 48 h but does not report the statistical method for handling measurements over time, whether each time point was analyzed separately, or whether a repeated-measures model was used. No such method should be inferred from the endpoint description alone.
The record specifies a standard deviation for the concentration outcome. In other settings, continuous data can be skewed or have variability that changes with the mean. In general, a method that assumes normally distributed observations or equal variability may not fit data that depart substantially from those assumptions. Over-dispersion means that observed variation is greater than a model expects; if present, it can make uncertainty appear smaller than it is when the model does not account for it. The registry does not report distributional checks, transformations, robust methods, or any concern about over-dispersion for this endpoint.
The sample-size assumptions described in the record are a planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is a stated fraction of the observed effect. In general, such illustrations depend on their assumptions and are not observed power. They do not indicate whether a study's findings are statistically significant, and they do not replace reporting the observed estimate and its uncertainty. No numerical sample-size illustration results or observed concentration effect estimates are reported in the registry record.
Finally, an analysis requires a defined population of observations. For example, investigators may analyze all participants who meet a prespecified definition or only those with particular measurements available. The registry record does not report an analysis population for the primary concentration endpoint, the number with measurements at each time, or a method for handling missing observations. These details are needed to judge how the summaries were formed and how broadly they apply.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure, with concentration measurements at 12, 18, 24, and 48 h. Multiple time points can create multiple opportunities for statistical comparisons. In general, when several hypotheses are tested, a prespecified approach to multiplicity can help control the chance of misleading conclusions from repeated testing. The registry does not report whether the time points were treated as separate tests, whether one was designated as the main comparison, or whether any multiplicity adjustment was planned.
No analyses are listed in the registry record. It does not report a statistical analysis plan, hypothesis tests, confidence intervals, or adjusted estimates for the primary outcome. Whether secondary analyses were planned, and how they would be distinguished from exploratory analyses, is not reported in the registry record.
The record does not describe missing-data handling or identify an analysis population for concentration measurements. It does not state how many participants contributed data at each time point, how incomplete measurement series were handled, or whether participants were excluded from any analysis. The stated outcome timeframe is hospital discharge or 7 days, whichever comes first, but the record does not explain whether measurement availability varied with that timeframe.
These omissions do not show that missing observations or multiplicity affected the findings; rather, the registry record does not provide enough information to assess either issue. The listed enrollment and planned group sizes do not establish the number of usable observations in the primary endpoint analysis.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Cases | 0 | 15 | 0.0% |
| Controls | 3 | 15 | 20.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Cases | 0 of 15 |
| Controls | 0 of 15 |
Most frequent serious adverse event terms
| Event term | Organ system | Cases | Controls |
|---|---|---|---|
| Surgical site infection | Surgical and medical procedures | 0 of 15 | 3 of 15 |
Serious events with the highest arm-level rate: surgical site infection (20.0%).
The registry lists 0 serious adverse events among 15 cases and 3 among 15 controls. It also identifies surgical site infection as the top serious term at 20.0%. These are reported group counts and a reported percentage; they should be read descriptively, not as evidence that one antibiotic approach caused more or fewer events.
The comparison is non-randomized, and the registry cautions that the groups are not a like-for-like control comparison. Differences in participant characteristics, care, or event ascertainment could affect a comparison. The record does not provide a statistical analysis of these safety counts, further detail about the event definitions, or an account of how events were collected. Death counts are not reported in the registry record. Other adverse events are listed as 0 among 15 in each group, but that listing does not supply additional detail about event types or monitoring.
12. What the Result Does, and Does Not, Mean
The record establishes that the study was designed to examine daptomycin concentrations during coronary artery bypass graft surgery without valvular replacement. It identifies mean concentrations at 12, 18, 24, and 48 h as the primary endpoint and names standard deviation as the dispersion measure. Those details define the intended measurement, but the registry does not report the concentration values or their uncertainty.
Accordingly, the posted registry information does not show the level or variability of daptomycin concentrations at any specified time. It also does not provide a reported statistical comparison between the cases and controls. Without these results, the primary pharmacokinetic question cannot be answered from the registry record.
The serious adverse-event entries show the counts recorded for the groups, including the listed surgical site infection term. They do not establish a causal effect. The non-randomized design and the registry's warning that the groups are not like-for-like make causal interpretation especially limited. The event counts should not be used to infer comparative risk or to conclude that either approach is safer.
In general, a registered study design and outcome definition are not equivalent to a complete results report. Interpretation of an estimate depends on the observed data, the analysis method, and the uncertainty around the estimate. Those primary concentration results and analyses are not reported in the registry record. The record therefore describes the research question and some safety counts, but does not establish a clinical or pharmacokinetic conclusion about the intervention.
13. Why This Trial Matters Statistically
This trial matters statistically because it illustrates the difference between defining an outcome and reporting its results. The registry specifies a continuous pharmacokinetic endpoint, its measurement unit, several measurement times, and a dispersion measure. Without the observed means, standard deviations, and numbers of observations, those specifications are not enough to assess the magnitude or precision of the endpoint.
The design also highlights why comparator structure affects interpretation. The registry describes a case group and a standard-of-care reference group, while recording non-randomized allocation and warning that the arms are not a like-for-like comparison. A numerical group contrast, if reported, would need to be interpreted in light of possible differences between groups rather than treated automatically as an intervention effect.
The safety entries offer another statistical lesson: counts can be reported without supporting a reliable causal comparison. Serious events are listed for both groups, but the registry does not provide a statistical analysis or additional event-collection details. Descriptive counts and causal evidence are not interchangeable.
Finally, the record underscores the value of reporting analysis populations, missing-data methods, and plans for interpreting multiple time points. Those details help readers judge what data contribute to an estimate and how uncertainty was handled. Their absence in the registry record limits the conclusions that can be drawn, even though the study question and intended measurements are clearly named.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most direct limitation is that the registry record does not report the primary concentration estimates, standard deviations, participant counts at each time point, or analyses. The stated pharmacokinetic question therefore cannot be answered from the posted results. Confidence intervals and statistical tests for the primary endpoint are also not reported in the registry record.
The design is non-randomized and open-label. The registry cautions that the case and control groups are not a like-for-like comparison, which limits interpretation of any between-group difference. Details about assignment, participant characteristics, the standard-of-care antibiotic regimen, and methods for adjusting for group differences are not reported in the registry record.
The endpoint description lists measurements at 12, 18, 24, and 48 h, while the outcome timeframe is hospital discharge or 7 days, whichever comes first. How these elements fit together, including whether participants contributed data at every time point, is not reported. The analysis population, missing-data procedures, distributional assessment, and handling of multiple time points are also not reported in the registry record.
Safety interpretation is limited by the available event information. The registry lists group counts and a serious-event term, but does not report event definitions, ascertainment details, or statistical comparisons. Death counts are not reported in the registry record. These limitations are specific to what the record documents and should not be taken as evidence that the unreported methods or data were absent from the study itself.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pharmacokinetics of Daptomycin During Cardiopulmonary Bypass Surgery — NCT00701636.
- Registry record last updated 2016-08-29; status last verified 2016-07.
- Results first posted 2016-08-29.
- 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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18. Record Summary
NCT00701636 is a completed, prospective, open-label pharmacokinetic study of daptomycin prophylaxis in coronary artery bypass graft surgery without valvular replacement. The registry lists Phase 3, non-randomized allocation, no masking, a single-group model, and enrollment of 30. The arm descriptions identify cases receiving daptomycin and controls receiving standard-of-care antibiotics.
The primary outcome is mean daptomycin concentration in mcg/ml at 12, 18, 24, and 48 h, with standard deviation specified as the dispersion measure. The timeframe is hospital discharge or 7 days, whichever comes first. The primary concentration results and analyses are not reported in the registry record. Serious adverse-event entries list 0 among 15 cases and 3 among 15 controls; surgical site infection is identified as the top serious term at 20.0%. The registry cautions that the groups are not a like-for-like control comparison.