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 Linezolid in Children With Cystic Fibrosis (NCT00625703), a na phase 2 study. The primary outcome is To Determine the Pharmacokinetic Profile of IV (Intravenous) and PO (Oral) Formulations of Linezolid Among Children With Cystic Fibrosis.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00625703 |
| Phase | Phase 2 |
| Condition | Cystic Fibrosis |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 45 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Texas Southwestern Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
Children with cystic fibrosis. The registry record says that outcome data are unavailable because the principal investigator was no longer at the institution and attempts to locate study personnel were unsuccessful.
Intervention
Linezolid, with the primary question referring to both intravenous and oral formulations. The record does not describe the dosing regimen or how participants received each formulation.
Comparator
No concurrent control group is recorded. The study is listed as single-group, and the registry warns that its arms are not a like-for-like control comparison.
Primary question
What pharmacokinetic profile do intravenous and oral linezolid formulations have among children with cystic fibrosis? The stated aim also includes establishing a dose regimen intended to be safe and effective, but the record does not report the findings needed to assess that aim.
In general, pharmacokinetics describes how drug concentrations change over time in the body. A study of more than one formulation may characterize concentration patterns for each formulation, but the registry record does not specify the measurements, sampling schedule, or comparison methods used. The record lists a primary-outcome timeframe of 2 months. It does not provide outcome values, estimates of uncertainty, or an analysis of the primary question. The separate secondary outcome concerns pulmonary exacerbations with methicillin-resistant Staphylococcus aureus (MRSA) in relation to linezolid treatment; no result for that outcome is reported.
3. Trial Design
The registry record describes a completed Phase 2 study with a single-group model and no masking. Allocation is listed as not applicable. Enrollment is recorded as 45, and the study condition is cystic fibrosis. The listed intervention is linezolid. The study start is recorded as 2010-12 and primary completion as 2011-05.
The primary objective was to determine the pharmacokinetic profile of intravenous and oral linezolid formulations among children with cystic fibrosis. The stated aim also included establishing a dose regimen intended to be safe and effective. These are objectives, not reported conclusions: the registry record contains no primary outcome data or analysis results.
A single-group study does not provide a concurrent control group for a like-for-like treatment comparison. The registry record explicitly notes that its arms are not a control comparison. It does not explain whether or how participants contributed data for both formulations, nor does it provide arm-level descriptions. The record also does not report the dose, route assignment, eligibility details, recruitment procedures, pharmacokinetic sampling schedule, or measurement methods.
The record lists a secondary outcome concerning pulmonary exacerbations with MRSA in relation to linezolid treatment. It does not report results for that outcome. Although the study status is completed, that status alone does not mean the planned outcomes or analyses are available in the registry. The number of analyses reported is 0.
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: No data available as PI is no longer at the institution. Several attempts were made to locate the PI or other study personnel associated with this study, but they were unsuccessful. Enrollment reflects the anticipated enrollment and actual enrollment is unknown due to PI is no longer at the institution.
Overall Study
| Stage | Linezolid: Pharmacokinetics |
|---|---|
| STARTED | 0 |
| COMPLETED | 0 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: No data are available as PI is no longer at the institution. Several attempts were made to locate the PI or other study personnel associated with this study, but they were unsuccessful
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: No data available as PI is no longer at the institution. Several attempts were made to locate the PI or other study personnel associated with this study, but they were unsuccessful. Enrollment reflects the anticipated enrollment and actual enrollment is unknown due to PI is no longer at the institution.
| Characteristic | Unit | Linezolid: Pharmacokinetics |
|---|---|---|
| Participants analysed | 0 | |
| Age, Categorical: <=18 years | — | |
| Age, Categorical: Between 18 and 65 years | — | |
| Age, Categorical: >=65 years | — | |
| Sex: Female, Male: Female | — | |
| Sex: Female, Male: Male | — |
6. Primary Endpoint
The registry lists the primary outcome as To Determine the Pharmacokinetic Profile of IV (Intravenous) and PO (Oral) Formulations of Linezolid Among Children With Cystic Fibrosis, measured over 2 months.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is described as determining the pharmacokinetic profile of intravenous and oral linezolid formulations among children with cystic fibrosis. In general, pharmacokinetic measurements characterize drug concentrations over time and can be used to describe how exposure varies by formulation or dosing conditions. The registry record does not name the specific pharmacokinetic parameters, measurement units, laboratory procedures, or summary method, so the exact operational definition of the endpoint is not reported in the registry record.
Pharmacokinetic outcomes are used to characterize drug exposure rather than directly to establish a clinical benefit. In general, a profile can inform consideration of dosing by describing concentration patterns, but interpreting it requires the relevant measurements, their timing, and a prespecified analysis. Those details and the primary outcome values are unavailable in the registry record. The listed timeframe is 2 months, but the record does not clarify the timing of individual measurements within that period.
The stated objective includes establishing a regimen intended to be safe and effective. That wording describes the study aim; it is not evidence that a regimen was established or that safety or effectiveness was demonstrated. No primary endpoint estimate, uncertainty interval, or statistical test result is reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the study objective and design but does not report the primary outcome data. Consequently, there is no posted estimate of the pharmacokinetic profile to interpret, no confidence interval describing its precision, and no analysis result addressing the primary question. The number of analyses reported is 0. The record states that outcome data are unavailable because the principal investigator was no longer at the institution and attempts to locate the investigator or other study personnel were unsuccessful.
The enrollment recorded is 45, but enrollment does not substitute for outcome information. Without reported measurements and an analysis, it is not possible to characterize the observed exposure, assess variability, or determine how precisely a pharmacokinetic parameter was estimated. Nor can the aim of establishing a dose regimen be treated as a result. The registry record does not report a regimen, its rationale, or supporting estimates.
The study is listed as single-group, with allocation not applicable and no masking. The registry record cautions that the arms are not a like-for-like control comparison. Accordingly, the design description does not support interpretation as a randomized comparison of linezolid against a control treatment. The record does not specify how the two formulations were assigned or compared, so it also does not support an assumption that a direct within-participant comparison was performed.
The secondary outcome concerns pulmonary exacerbations with MRSA in relation to linezolid treatment, but no outcome result is reported. The adverse-event entry lists 0 at risk and 0 affected in its listed categories; because the registry record provides no participant-level safety data or explanation for those entries, they should not be read as demonstrating an absence of adverse events.
Any planning illustration based on an observed effect must be interpreted cautiously when the outcome results needed to identify that effect are not available in the registry record. Such an illustration is not the trial's original sample-size justification and is not observed power. The record does not report a protocol-based sample-size rationale, interim analyses, or a statistical analysis plan.
9. Statistical Methods Explained
In general, a pharmacokinetic analysis describes drug exposure using measured concentrations over time. Depending on the research question, an analysis may summarize concentration patterns or derive parameters from those measurements. The registry record names the broad objective—determining the profile of intravenous and oral linezolid—but does not identify the parameters, units, sampling times, assay, or model. Those omissions prevent a reader from determining exactly what was measured or how the primary outcome was defined in practice.
What does a confidence interval add?
In general, a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the analysis. Its width reflects how precisely the quantity has been estimated; it does not by itself show whether a finding is clinically important or whether a treatment works. No primary estimate or confidence interval is reported in the registry record, so the precision of the study's pharmacokinetic findings cannot be assessed from that record.
What can a single-group design establish?
In general, a single-group study can describe measurements collected in the group studied. Without a suitable concurrent comparison, it does not provide the same basis for separating a treatment-related change from other explanations as a controlled comparison. The registry record identifies this study as single-group and expressly warns that its arms are not a like-for-like control comparison. It does not describe the arrangement of participants across formulations, so further assumptions about the comparison would be unwarranted.
Masking is listed as none. In general, masking can reduce the influence of knowledge about treatment assignment on some aspects of study conduct or assessment. Its relevance depends on the outcome and procedures. The record does not explain which personnel knew treatment details, whether concentration measurements were processed without treatment information, or whether any outcome assessment could have been influenced by knowledge of treatment.
How should planning illustrations be read?
In general, a sample-size calculation asks how much information a proposed study might need under specified assumptions about an effect, variability, allocation, and statistical method. A planning illustration based on an observed effect is a retrospective illustration, not evidence that the original study was designed around that effect. It is also not observed power, which is not a substitute for reporting an estimate and its uncertainty. The registry record describes planning assumptions of a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. It also distinguishes total events for time-to-event illustrations from participants per arm for other illustrations. However, the underlying observed effect is not reported in the registry record, and the study is listed as single-group rather than a like-for-like two-arm comparison. The record does not report the study's own sample-size justification. These planning assumptions therefore should not be mistaken for the trial's design or observed results.
For count outcomes, general statistical methods may account for over-dispersion when the data vary more than a simpler model expects. For continuous measurements, an analysis may need to account for repeated measurements or differing variability. These are general considerations, not descriptions of methods used in this study: the registry record does not identify a statistical model, distributional assumptions, adjustment variables, or methods for repeated pharmacokinetic measurements.
Likewise, a p-value, when reported, describes the compatibility of data with a specified statistical model and null hypothesis; it does not quantify the probability that a treatment works. No p-value or test result for the primary outcome is reported. With no posted endpoint estimate or analysis details, recalculation from summary statistics is not possible from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists a primary pharmacokinetic objective and a secondary outcome concerning pulmonary exacerbations with MRSA in relation to linezolid treatment. It does not report a multiplicity strategy, such as a hierarchy among outcomes or an adjustment for conducting multiple tests. The statistical analysis plan is not reported in the registry record. Without that information, the intended handling of multiple outcome questions cannot be assessed.
Outcome data are unavailable in the record. It says that the principal investigator was no longer at the institution and attempts to locate the investigator or other study personnel were unsuccessful. The record does not describe whether data were collected, which measurements were missing, why any measurements might be missing, or how missing values were handled. It also does not report participant flow through analysis or the number of observations contributing to any endpoint.
The analysis populations are not reported in the registry record. There is no description of an intention-to-treat population, a per-protocol population, or a pharmacokinetic analysis set. These labels should not be inferred from the single-group design or the enrollment entry.
The adverse-event record lists 0 at risk and 0 affected in the listed categories, but gives no further explanation of the entries. Those entries cannot establish that safety data were complete or that no events occurred. Overall, missing outcome and analysis information limits assessment of both the planned statistical approach and the completeness of reporting.
11. What the Result Does, and Does Not, Mean
The registry record establishes that a completed Phase 2, single-group study was intended to characterize intravenous and oral linezolid pharmacokinetics among children with cystic fibrosis. It records enrollment as 45 and gives a primary-outcome timeframe of 2 months. It also identifies a secondary outcome related to pulmonary exacerbations with MRSA.
Those design and objective details are not outcome findings. The primary results, statistical estimates, and analyses are not reported in the registry record. Therefore, readers cannot tell from this record what pharmacokinetic profile was observed, how variable the measurements were, or how precise any estimate might be. The record also cannot establish whether a dose regimen was derived from the study findings. The stated aim of establishing a regimen intended to be safe and effective should not be mistaken for evidence that this aim was achieved.
The single-group design and the registry's warning about non-comparable arms also matter. The record does not offer a like-for-like control comparison from which to interpret a relative treatment effect. No conclusion about efficacy or comparative safety follows from the study description alone. The secondary clinical outcome has no reported result, and the adverse-event entries do not provide an interpretable account of events.
In general, a registry entry is useful for identifying a study's stated aims and recorded design, but a completed status does not ensure that results are available in the record. Here, the missing outcome and analysis information means that the statistical evidence cannot be evaluated from the registry record. It is not possible to characterize the direction, magnitude, or precision of findings that are not reported.
12. Why This Trial Matters Statistically
This study raises a useful statistical distinction between a pharmacokinetic objective and a clinical outcome question. In general, concentration measurements characterize exposure, while outcomes such as pulmonary exacerbations address clinical events. The registry record includes both kinds of objectives, but does not report results for either. Keeping those questions distinct prevents a stated pharmacokinetic aim from being treated as demonstrated clinical benefit.
The record also illustrates why design labels need to be read alongside the comparison structure. A single-group study may describe measurements, but the registry explicitly cautions that its arms are not a like-for-like control comparison. A reader should not infer a randomized contrast simply because more than one formulation is named. The record does not specify how the formulations were handled analytically.
Statistical interpretation depends on more than enrollment and completion status. Estimates, uncertainty, analysis populations, methods, and missing-data information are needed to assess what the data support. Here, the recorded enrollment is 45, yet the outcome data and analyses are unavailable. Thus, the record's most important statistical feature is the gap between a clearly stated research objective and the absence of results with which to evaluate it.
Finally, planning calculations and observed findings answer different questions. General sample-size illustrations can explore assumptions, but they cannot replace a reported effect estimate or the study's own design rationale. The registry record does not report that rationale, and its outcome information is insufficient to assess an observed effect.
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 interpretation is that the registry record does not contain outcome data or analysis results. It states that the data are unavailable because the principal investigator was no longer at the institution and attempts to locate the investigator or other study personnel were unsuccessful. Without results, the pharmacokinetic objective and the secondary clinical outcome cannot be evaluated.
Descriptions needed to assess methods are also absent. The record does not specify the pharmacokinetic parameters, measurement units, sampling schedule, assay, dose regimen, or formulation assignment. It gives no analysis model, adjustment strategy, missing-data method, or analysis-population definition. The record also does not report a sample-size justification, interim analyses, or a statistical analysis plan.
The design is listed as single-group, with no masking and allocation not applicable; the registry cautions that arms are not a like-for-like control comparison. This limits what can be inferred about comparative effects from the design description. The record does not explain how the two formulations relate to the study's participants or analyses.
Safety reporting is difficult to interpret: the adverse-event entry lists 0 at risk and 0 affected in the listed categories, without further context. Those entries do not establish that safety information is complete or that no adverse events occurred. The completed status and enrollment entry do not resolve these limitations or substitute for the missing outcome results.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Pharmacokinetics of Linezolid in Children With Cystic Fibrosis — NCT00625703.
- Registry record last updated 2020-03-27; status last verified 2020-03.
- Results first posted 2020-03-27.
- 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 record describes NCT00625703, a completed Phase 2, single-group study sponsored by the University of Texas Southwestern Medical Center. It lists cystic fibrosis as the condition, linezolid as the intervention, enrollment of 45, no masking, and allocation as not applicable. The study start is recorded as 2010-12 and primary completion as 2011-05.
The primary objective was to determine the pharmacokinetic profile of intravenous and oral linezolid among children with cystic fibrosis; the listed timeframe is 2 months. A secondary outcome concerns pulmonary exacerbations with MRSA in relation to linezolid treatment. The registry record reports no analyses and says outcome data are unavailable after unsuccessful attempts to locate study personnel. It does not provide endpoint results, a statistical analysis plan, or an interpretable safety analysis.