A Pilot Study of Daptomycin for Antimicrobial Prophylaxis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Pilot Study of Daptomycin for Antimicrobial Prophylaxis (NCT00572260), a na phase 4 study. The primary outcome is Rate of Patients Receiving Antimicrobial Prophylaxis Within the Appropriate Timeframe Before Incision.

2. Clinical Question

The study was framed as a pilot assessment of feasibility, surgical site infection rates, and adverse events. Its primary endpoint focused on whether prophylaxis was administered at the intended time, rather than on a randomized comparison of clinical outcomes. The registry record lists 11 participants enrolled, but says the study closed because the principal investigator departed and data analysis was not performed. It therefore does not report a primary-outcome rate or a result for surgical site infections.

The record associates the primary outcome with a timeframe of 30 days after surgery, although the outcome itself concerns administration before incision. That label does not supply a measured result or clarify how the timing outcome was assessed. The intervention and study question can be described, but the registry record does not report an analyzed estimate answering the primary question.

3. Trial Design

NCT00572260 is recorded as a Phase 4, single-group pilot study sponsored by Duke University. The registry lists an enrollment of 11 and describes daptomycin prophylaxis for patients undergoing cardiac valve replacement or coronary artery bypass grafting who were considered at increased risk for MRSA infection. The stated goals were to evaluate feasibility, determine surgical site infection rates, and evaluate adverse events.

The intervention was described as a single preoperative dose of daptomycin, administered within 30 minutes before surgery. The arm description specifies 6 mg/kg IV for patients with creatinine clearance ≥ 30 ml/min. The record lists no masking and allocation as not applicable. There is no control arm, so this design does not support a direct randomized comparison with another prophylactic approach.

The study start is recorded as 2008-01 and primary completion as 2008-09. Its status is terminated. The registry states that it closed due to the departure of the principal investigator and that data analysis was not performed. That explanation identifies why the study ended without analysis; further information about the termination process is not reported in the registry record.

The single-group structure is relevant to interpretation. Any observed event counts describe participants in the daptomycin group, but there is no concurrent comparison group against which to estimate a treatment contrast. The record does not report a protocol-based statistical analysis plan, a sample-size justification, or an inferential analysis. The small enrollment and absence of analyzed primary results leave the intended feasibility question unanswered 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: Between 1/17/2008 and 9/15/2008, among the 12 study subjects that signed the ICF, 11 subjects met the eligibility criteria and were enrolled in the study. One subject was disqualified due to weight \> 150kg and was withdrawn from the study

Overall Study

Analysis population for the primary outcome, as defined in the registry: The study closed due to the departure of the principal investigator and the data analysis was not performed.

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 Patients Receiving Antimicrobial Prophylaxis Within the Appropriate Timeframe Before Incision, measured over 30 days after surgery.

The primary endpoint is the rate of patients receiving antimicrobial prophylaxis within the appropriate timeframe before incision. It concerns the timing of administration: whether prophylaxis was given early enough in relation to surgery, rather than whether the drug reduced infection or improved another clinical outcome.

As a general statistical concept, a timing endpoint can help evaluate whether an intervention is operationally feasible. If the required administration window is missed, a treatment strategy may be difficult to implement as intended. A rate would describe the proportion of participants meeting the timing criterion, but interpreting such a rate requires a clear definition of the eligible population, the timing rule, and how missing administration records are handled. Those details are not reported in the registry record.

The record gives the outcome timeframe as 30 days after surgery, while the endpoint title refers to administration before incision. This pairing leaves the precise measurement window unclear. More importantly, the registry states that data analysis was not performed. No primary-endpoint count, rate, or estimate is reported, so the intended feasibility measure cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the single-group design allow?

The registry describes a single-group study with no masking and allocation listed as not applicable. In general, a single-group design records outcomes among participants receiving an intervention without a concurrent control group. It can be used to describe implementation or observed events, but it does not directly estimate how outcomes compare with another treatment or with no intervention. Differences between participants, changes over time, and other influences cannot be separated from the intervention by a randomized comparison when no such comparison is present.

Here, the primary question is about whether prophylaxis was administered within the intended timeframe. A descriptive rate could have answered that operational question if the relevant participant-level information had been analyzed. The registry says data analysis was not performed, and it reports no endpoint result. Thus, neither a descriptive primary rate nor a comparative estimate is available.

What would a rate mean?

As a general statistical concept, a rate or proportion for a binary endpoint summarizes how many participants met a defined criterion relative to the eligible group. Interpretation depends on a prespecified definition of success, a clear denominator, and consistent outcome ascertainment. For a pre-incision timing measure, the criterion would need to specify what counts as the appropriate window and how administration time is documented. The registry record does not report these operational details or an analyzed numerator and denominator for the primary outcome.

The endpoint timeframe is listed as 30 days after surgery, although the outcome title concerns the time before incision. The record does not explain this relationship. It is therefore not possible to determine from the entry whether that timeframe refers to outcome ascertainment, follow-up, or another registry convention. No assumption about the endpoint’s actual measurement procedure should be made.

Why are inferential statistics unavailable?

Inferential methods quantify uncertainty around an estimate or assess a hypothesis under stated assumptions. A confidence interval describes the range of estimates reasonably compatible with the observed data and model. A p-value evaluates how unusual data would be under a specified null hypothesis and analysis procedure. Neither can be interpreted without an analyzed outcome and an appropriate statistical method. The registry reports zero analyses and says analysis was not performed; it therefore gives no primary estimate, confidence interval, or p-value.

For a comparison between groups, the analysis would also need to define the contrast, account for the design, and describe any adjustment for relevant factors. This trial has no comparator group, and an adjusted or comparative analysis is not reported. General statistical methods cannot create a missing comparison or recover an unreported primary result.

How should planning calculations be read?

The record describes planning illustrations based on a stated fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These assumptions describe hypothetical planning calculations, not the observed design: the registered study is single-group and has no two-arm allocation. The illustrations are not observed power. A sample-size planning calculation is a prospective aid under chosen assumptions; it does not show that a study had a particular probability of finding a result after the data were collected.

Planning calculations also depend on the effect size and other assumptions used. If those assumptions differ from what occurs in practice, the resulting target may not correspond to the actual study conditions. The registry record does not report a trial-specific sample-size justification, the rationale for enrolling 11 participants, or a planned detectable effect. No unreported design rationale should be inferred from the illustration assumptions.

What does over-dispersion mean in general?

For count outcomes, over-dispersion means that the observed variability exceeds what a chosen statistical model expects. When present, it can make standard errors too small if the model does not account for the extra variability, leading to overly narrow confidence intervals or misleading tests. This is a general issue in count-data analysis, not a finding about this study. The registry does not report an analyzed count outcome, a model for such an outcome, or any assessment of over-dispersion.

What can the safety counts support?

The posted safety information is descriptive: it lists the participants at risk and the numbers affected in serious and other adverse-event categories. Such counts can communicate what was recorded, but by themselves they do not measure comparative risk. A more complete safety interpretation would require details such as event definitions, follow-up completeness, ascertainment procedures, and the analysis population. Those details are not reported in the registry record. The absence of a reported event in a small group does not establish that the event is impossible or that safety has been fully characterized.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, focused on the rate of patients receiving antimicrobial prophylaxis within the appropriate timeframe before incision. The study summary also identifies feasibility, surgical site infection rates, and adverse events as goals. The record does not explain how these goals relate to formal primary or secondary analyses, or whether any outcomes were designated for confirmatory testing.

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are considered. In general, examining many results can increase the chance of a misleading positive finding unless the analysis plan addresses that issue. The registry record does not report a multiplicity strategy, planned hierarchy of outcomes, or statistical testing plan. Since no data analysis was performed, there are no reported hypothesis tests for which an adjustment can be assessed.

Information about missing outcome data is also not reported in the registry record. The statement that data analysis was not performed does not reveal whether participant-level measurements were incomplete, unavailable, or simply unanalyzed. The record does not describe how missing values would have been handled.

Analysis populations are not reported in the registry record. There is no description of an intention-to-treat, per-protocol, treated, or safety population for the primary outcome. The adverse-event counts identify 11 participants at risk in the listed group, but that alone does not define the population used for every intended analysis. Without population definitions and outcome completeness information, the denominator and potential selection effects for an analyzed primary endpoint cannot be evaluated.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event record lists 0 serious adverse events among 11 participants at risk in the daptomycin prophylaxis group. It also lists 0 participants affected in the separate other adverse-event category among 11 at risk. No serious adverse-event terms are listed. Deaths are not reported in the registry record.

These figures describe the entries recorded for the listed group. They do not establish that adverse events were absent throughout all relevant follow-up, or that the intervention has no safety risks. A zero count can occur even when an event is possible, particularly in a study with limited enrollment. The record does not report the duration or completeness of safety monitoring, the definitions used for the categories, or a detailed account of event collection.

The study’s summary says that adverse-event occurrence was a goal, but the registry also states that data analysis was not performed. The posted counts should therefore be read as limited descriptive safety information, not as a comparative safety analysis. With no comparator group, the figures cannot quantify how adverse-event experience differed from another approach.

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

The registry record establishes that NCT00572260 was a pilot study of daptomycin prophylaxis in cardiac surgery patients at increased risk for MRSA infection. It documents a single-group design, enrollment of 11, the intended preoperative administration, and termination after the principal investigator departed. It also records limited adverse-event counts.

It does not establish whether prophylaxis was administered within the appropriate timeframe before incision. That is the primary outcome, but the registry says data analysis was not performed and reports no primary result. The record likewise does not report analyzed surgical site infection rates, although evaluating those rates was among the study goals. The absence of a result should not be treated as a negative finding or as evidence that the intervention did or did not meet the study objective.

The single-group design also limits what any descriptive results could establish. Without a comparator, observed outcomes cannot be attributed to daptomycin by comparison with another strategy. The record contains no reported comparative effect estimate, confidence interval, or hypothesis test.

The serious and other adverse-event entries show 0 affected participants among 11 at risk in each listed category. Those counts are descriptive and do not demonstrate that risk is absent. Follow-up details and other safety-analysis information are not reported in the registry record.

In general, a pilot study can inform whether study procedures are feasible, but its interpretation depends on the outcomes actually collected and analyzed. In this case, the registry’s explicit statement that analysis was not performed means the central feasibility result is unavailable. The record documents the question and conduct of the study, not an answer to that question.

13. Why This Trial Matters Statistically

This study is statistically notable because its primary question concerns implementation: whether prophylaxis was delivered within a specified pre-incision timeframe. Such a question differs from a comparative efficacy question. A timing outcome can describe whether a procedure was carried out as intended, but it still requires a clear operational definition, complete timing information, and a reported analysis.

The registry provides the design and enrollment context but says the analysis was not performed. That makes the distinction between a planned endpoint and an observed result especially important. Naming an outcome does not mean that a result was generated, and the absence of a reported rate cannot be interpreted as a rate of zero or as proof of feasibility.

The single-group design also illustrates a basic limit of descriptive evidence. Counts in one group can document observed experience, but a treatment contrast requires a meaningful comparator and an analysis designed to estimate that contrast. Because there is no comparator, the study cannot establish how outcomes would differ under another prophylactic approach.

Finally, the limited safety counts show why denominators, follow-up, and analysis populations matter. The record lists 0 affected participants in the serious and other categories among 11 at risk, but does not give fuller safety methods or follow-up detail. These figures are informative as registry entries, yet they cannot by themselves characterize comparative risk or rule out uncommon events. The study therefore serves as a case in separating descriptive counts, feasibility questions, and causal comparisons.

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 main limitation specific to this study is that the registry states data analysis was not performed. As a result, the primary outcome has no reported estimate, and the study’s stated goals of assessing feasibility and surgical site infection rates are not answered by an analyzed result in the record.

The design was single-group, with no comparator and no masking. This means there is no randomized contrast for evaluating outcomes against another prophylactic approach. The registry does not report a statistical analysis plan, a trial-specific sample-size justification, or a rationale for the enrollment of 11 participants.

The primary outcome’s listed timeframe is 30 days after surgery, while its title refers to administration before incision. The registry does not explain this timing label or report the detailed outcome definition, assessment procedures, or denominator for the intended rate. Missing-data handling and analysis-population definitions are also not reported in the registry record.

Safety information is limited to the listed counts: 0 serious events and 0 events in the other category among 11 at risk. Serious-event terms are not listed, and deaths are not reported. The record does not describe the duration or completeness of adverse-event follow-up, event ascertainment, or a comparative safety analysis.

The study status is terminated, and the record attributes closure to the principal investigator’s departure. Additional details about study conduct after closure or the availability of unanalyzed data are not reported in the registry record. These limitations restrict interpretation to the documented design and counts; they do not support conclusions about unreported outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Pilot Study of Daptomycin for Antimicrobial Prophylaxis — NCT00572260.
• Registry record last updated 2014-07-25; status last verified 2012-11.
• Results first posted 2012-12-03.
• 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.

18. Record Summary

NCT00572260 was a Phase 4, single-group pilot study sponsored by Duke University. It enrolled 11 patients undergoing cardiac valve replacement or coronary artery bypass grafting who were at increased risk for MRSA infection. The intervention was a single preoperative daptomycin dose, with the arm description specifying 6 mg/kg IV when creatinine clearance was ≥ 30 ml/min.

The primary outcome concerned the rate of prophylaxis administration within the appropriate timeframe before incision. The registry record lists a 30 days after surgery timeframe, but reports no primary result. It states that the study closed because the principal investigator departed and that data analysis was not performed. The recorded serious and other adverse-event counts were 0 among 11 at risk in each category; deaths are not reported.