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 The Study Of Azithromycin Switch Therapy For Treatment Of Community Acquired Pneumonia (CAP) (NCT00809328), a non-randomized phase 3 study. The primary outcome is Response Rate (Clinical Response, Data Review Committee Assessment).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00809328 |
| Phase | Phase 3 |
| Condition | Community Acquired Pneumonia (CAP) |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 102 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Japanese adult subjects with community acquired pneumonia who required initial intravenous therapy. The listed clinical per protocol population included subjects who received at least one dose, had no significant protocol violation, and underwent prescribed evaluations during the observation period.
Intervention
Azithromycin switch therapy: intravenous azithromycin followed by oral administration.
Comparator
There was no comparator arm. The study was non-randomized and single-group, so it does not provide a like-for-like control comparison.
Primary question
What percentage of participants in the clinical per protocol set were assessed as effective for clinical response by the Data Review Committee at the specified endpoint timeframe?
The study asks a descriptive question about clinical response during a switch regimen, rather than a comparative question about whether azithromycin differs from another treatment. The primary outcome is defined as a response rate, using the number assessed as effective relative to the total assessed, after excluding those assessed as indeterminate. The endpoint timeframe is End of Treatment, Day 15 and Day 29.
That question is narrower than a claim about all adults with pneumonia. The official study title specifies Japanese adult subjects with community acquired pneumonia requiring initial intravenous therapy, while the analysis population further depends on treatment receipt, protocol adherence, and completion of prescribed evaluations. The registry record does not report the primary response-rate result, so it is not possible to describe the observed level of response or its precision from the posted results.
With no comparison group and no random allocation, the study cannot separate changes associated with the regimen from the natural course of illness, other care, or selection into the analysis population. The clinical question can therefore be read as an assessment of outcomes in the enrolled study group, not as a causal estimate of benefit relative to an alternative.
3. Trial Design
This was a Phase 3, multicenter, non-randomized, open-label, single-group study of azithromycin switch therapy. The regimen involved intravenous azithromycin followed by oral administration. The official title identifies the population as Japanese adult subjects with community acquired pneumonia requiring initial intravenous therapy. Enrollment was 102. The registry lists the study as completed, with a start of 2009-02 and primary completion of 2010-03.
A single-group design means that all participants were assigned to the same study regimen, rather than to separate treatment and control groups. The non-randomized allocation and absence of masking are consistent with that design description. Because there is no concurrent comparator, outcomes can be described for the study group, but treatment differences against another regimen cannot be estimated from this trial alone. The study does not establish what would have happened to comparable participants under a different treatment or under a control condition.
Open-label means that treatment was not masked in the study design. Knowledge of treatment can matter for outcomes that require judgment, such as clinical response assessments. The primary response was assessed by a Data Review Committee, while some secondary measures specify investigator assessment. The registry record does not report further information about assessor blinding or procedures for resolving differing assessments.
The registry lists one intervention, azithromycin, and one arm, described as switch therapy from intravenous to oral administration. It does not report a separate control arm. The design features therefore support a descriptive reading: the record concerns outcomes observed during this regimen in a specified study population. They do not support a randomized treatment-effect interpretation. Further details about the protocol, including any design rationale or sample-size justification, 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.
Overall Study
| Stage | Azithromycin |
|---|---|
| STARTED | 102 |
| COMPLETED | 73 |
| NOT COMPLETED | 29 |
Reasons for not completing this period:
| Reason | Azithromycin |
|---|---|
| Lack of Efficacy | 18 |
| Adverse Event | 6 |
| Protocol Violation | 3 |
| Withdrawal by Subject | 2 |
Analysis population for the primary outcome, as defined in the registry: Clinical per protocol set consisted of all subjects who received at least one dose of the study drug, have no significant violation of protocol, and underwent prescribed evaluations during the observation period. No imputation was used for missing data. "n " in the measured values means total participants excluding ones assessed as indeterminate.
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 | Azithromycin |
|---|---|---|
| Participants analysed | 102 | |
| Age Continuous | years | 55.4 (SD 18.6) |
| Sex: Female, Male: Female | Participants | 39 |
| Sex: Female, Male: Male | Participants | 63 |
6. Primary Endpoint
The registry lists the primary outcome as Response Rate (Clinical Response, Data Review Committee Assessment), measured over End of Treatment, Day 15 and Day 29.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the Response Rate (Clinical Response, Data Review Committee Assessment). It is expressed as a percentage of participants and has a 95% Confidence Interval as its stated dispersion measure. The specified timeframe is End of Treatment, Day 15 and Day 29.
The registry description defines the response rate as the number of participants assessed as effective divided by the total participants, excluding those assessed as indeterminate, multiplied by 100. This definition makes the handling of indeterminate assessments part of the endpoint itself: they are not included in its denominator. The analysis population is described as the clinical per protocol set, consisting of subjects who received at least one dose, had no significant protocol violation, and underwent the prescribed evaluations during the observation period.
A response rate is useful for describing how often a defined outcome was observed in a study group. The confidence interval is intended to convey the statistical uncertainty around that percentage; it does not address whether the endpoint definition is clinically appropriate, whether the study population represents other patients, or whether the treatment caused the outcome.
The registry record does not report the response-rate estimate or confidence-interval limits. It therefore gives the endpoint definition and timeframe, but not the numerical result needed to assess the observed response rate or its precision. It also does not report additional details about the committee’s assessment criteria beyond the endpoint description.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The study’s primary outcome is a clinical response rate in a single group receiving intravenous azithromycin followed by oral azithromycin. The registry record identifies the endpoint, population, and assessment timeframe, but does not report the numerical response rate or its 95% confidence interval. Consequently, the posted record does not support a quantitative account of the primary clinical outcome. No point estimate, interval width, or degree of statistical precision should be inferred from the endpoint description alone.
This absence is especially important when interpreting a single-group study. A response proportion can describe the frequency of observed responses in the analyzed group, but without a comparator it cannot show how that frequency would differ under another treatment or control condition. Even a reported response rate would not by itself distinguish the regimen’s contribution from other influences, such as the course of illness, other care, or characteristics of participants who qualified for the clinical per protocol set.
The study was non-randomized and open-label. These features do not invalidate descriptive outcome reporting, but they limit causal interpretation. In an open-label setting, judgments about clinical response may be influenced by knowledge of treatment unless suitable safeguards are used. The primary assessment is attributed to a Data Review Committee, but further information about masking or assessment procedures is not reported in the registry record. That omission means the committee label alone should not be taken as evidence that assessments were blinded.
The endpoint denominator excludes participants assessed as indeterminate. This is part of the stated response-rate definition and affects how the percentage should be understood. A rate based on determinate assessments may differ from one calculated using all participants, but the registry does not report the counts for effective, ineffective, or indeterminate assessments. It also does not report the primary endpoint’s numerical result, so the practical effect of this denominator rule cannot be evaluated.
The record names four secondary outcomes: clinical improvement by investigator assessment, bacteriological eradication by Data Review Committee assessment, and bacteriological eradication by investigator assessment, in addition to the response-rate primary endpoint. Their numerical findings are not reported in the registry record. There are no analysis records listed. Thus, neither the primary result nor the pattern of secondary results can be evaluated from the posted information.
The sample-size material should be interpreted as planning illustrations rather than evidence about trial performance. Its stated assumptions describe hypothetical two-arm calculations using equal allocation, a two-sided significance level of 0.05, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. These assumptions do not describe the actual single-group design, and the illustrations are not observed power. The registry does not report the trial’s own sample-size justification. Since the primary outcome estimate is not reported, the observed effect underlying any such illustration cannot be assessed from the registry record.
Overall, the record supports a description of the study design and endpoint specification, but not a conclusion about the magnitude or precision of the clinical response. It also does not support a comparative or causal treatment claim. A cautious reading keeps those distinctions separate: a defined outcome was intended to be measured, but the numerical outcome and the information needed to judge comparative effectiveness are not reported in the registry record.
9. Statistical Methods Explained
The primary outcome is a binary-response measure summarized as a percentage. For each participant included in the endpoint calculation, the assessment is categorized according to whether clinical response was effective, ineffective, or indeterminate. The registry definition counts participants assessed as effective in the numerator and excludes those assessed as indeterminate from the denominator. The resulting quantity is described as a response rate, expressed as a percentage of participants.
What does the confidence interval communicate?
In general, a confidence interval describes uncertainty around an estimate under the statistical method used to construct it. For a response percentage, the interval gives a range of values that are compatible with the observed data and that method’s assumptions. A narrower interval generally indicates greater statistical precision than a wider interval. It is not a guarantee that the true value lies inside the particular interval, and it does not correct for bias, limitations in the population, or a weak study design.
The registry identifies a 95% Confidence Interval as the dispersion measure for the primary outcome, but the interval limits and the response-rate estimate are not reported in the registry record. The method used to calculate the interval is also not reported. Without the estimate and interval, readers cannot assess the response proportion’s numerical size or the uncertainty around it.
What does the analysis population mean?
The primary population is described as the clinical per protocol set. It includes subjects who received at least one dose of study drug, had no significant protocol violation, and underwent prescribed evaluations during the observation period. This is a defined analysis population, not simply an automatic count of everyone enrolled. Restricting analysis to participants meeting these criteria can make the endpoint population different from the enrollment group. The registry record does not report the size of the clinical per protocol set.
The endpoint description states that no imputation was used for missing data. In general, imputation replaces missing values with estimates under an explicit method, whereas an analysis without imputation does not fill in missing endpoint values in that way. The record does not explain how missing assessments were classified or whether all such cases were excluded, nor does it give the number of missing or indeterminate assessments. It would therefore be inappropriate to assume that missing and indeterminate assessments were treated as the same category.
Why does the design affect interpretation?
Randomization is generally used to make treatment groups comparable with respect to measured and unmeasured factors, on average. This study was non-randomized and single-group, so there is no randomized comparison and no concurrent control group. Its response percentage is descriptive of the analyzed group. It cannot, on its own, estimate a contrast between the regimen and an alternative.
Masking can reduce the influence of treatment knowledge on subjective decisions. The study is listed as open-label, and the primary endpoint relies on a clinical response assessment. The attribution of assessment to a Data Review Committee identifies who assessed the endpoint, but the record does not report whether the committee was masked to treatment or what procedures were used to limit assessment bias.
How should the planning assumptions be read?
The record describes sample-size calculations as planning illustrations based on an observed effect, not as the trial’s original design calculations. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are hypothetical planning choices; they do not turn a single-group study into a randomized two-arm study and do not represent observed power.
Sample-size planning asks how many participants per arm might be needed under specified assumptions to detect a particular effect with a chosen probability of detection. Such a calculation depends on the assumed effect, outcome variability, allocation, and analysis method. A planning illustration is not a result about whether the completed trial had adequate power. The registry record does not report the trial’s own sample-size justification, and it does not report the primary response-rate estimate needed to evaluate an effect-based illustration.
More generally, methods should be interpreted in relation to the design and the reported results. A confidence interval can quantify sampling uncertainty for a percentage, but not eliminate selection or assessment bias. A per protocol analysis can describe outcomes among participants meeting its criteria, but does not necessarily represent everyone enrolled. An unadjusted descriptive estimate from one group cannot provide the causal contrast that a controlled comparison is designed to estimate. In this record, the endpoint definition is available, but key numerical results and several methodological details are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists five outcome measures in total: the primary clinical response assessed by the Data Review Committee and four secondary measures. The secondary measures are clinical improvement assessed by investigators, bacteriological eradication assessed by the Data Review Committee, and bacteriological eradication assessed by investigators, with eradication listed separately for the two assessment sources. The registry record lists no analyses.
When a study evaluates multiple outcomes or makes multiple statistical comparisons, the chance of at least one apparently notable result can increase. General approaches to multiplicity include prioritizing a primary endpoint, adjusting statistical thresholds, or treating secondary findings as exploratory. The registry record does not report a multiplicity adjustment or a statistical testing hierarchy. It would therefore be unwarranted to assume that secondary findings were adjusted, confirmatory, or formally tested according to a prespecified sequence.
Missing data are addressed in the primary population description: no imputation was used. The record does not report the amount of missing data, how missing assessments were handled in practice, or whether any sensitivity analyses were conducted. The response-rate definition also excludes participants assessed as indeterminate. Since counts for these categories are not reported, readers cannot determine how many assessments contributed to the denominator or how exclusions may have affected the result.
The analysis population is the clinical per protocol set, defined by treatment receipt, protocol adherence, and completion of prescribed evaluations. The registry does not report its size or a comparison between that set and all enrolled participants. Such information would help readers understand the extent to which the primary analysis reflects the enrolled study group. The primary estimate, confidence interval, secondary outcome results, and analysis details are not reported in the registry record.
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 |
|---|---|---|---|
| Azithromycin | 8 | 102 | 7.8% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 2% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Azithromycin | 33 of 102 |
Most frequent serious adverse event terms
| Event term | Organ system | Azithromycin |
|---|---|---|
| Pneumonia | Infections and infestations | 3 of 102 |
| Cardiac failure congestive | Cardiac disorders | 1 of 102 |
| Peritonsillar abscess | Infections and infestations | 1 of 102 |
| Prothrombin time prolonged | Investigations | 1 of 102 |
| Lung neoplasm malignant | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 1 of 102 |
| Organising pneumonia | Respiratory, thoracic and mediastinal disorders | 1 of 102 |
| Pneumothorax | Respiratory, thoracic and mediastinal disorders | 1 of 102 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Azithromycin |
|---|---|---|
| Diarrhoea | Gastrointestinal disorders | 15 of 102 |
| Constipation | Gastrointestinal disorders | 8 of 102 |
| Headache | Nervous system disorders | 8 of 102 |
| Injection site pain | General disorders | 6 of 102 |
| Insomnia | Psychiatric disorders | 6 of 102 |
| Injection site erythema | General disorders | 3 of 102 |
| Back pain | Musculoskeletal and connective tissue disorders | 3 of 102 |
| Haemoptysis | Respiratory, thoracic and mediastinal disorders | 3 of 102 |
Serious events with the highest arm-level rate: pneumonia (2.9%), cardiac failure congestive (1.0%), peritonsillar abscess (1.0%), prothrombin time prolonged (1.0%), lung neoplasm malignant (1.0%).
The registry adverse-event information lists 8 participants affected by serious adverse events among 102 at risk in the Azithromycin group. It lists 33 participants affected by other adverse events among 102 at risk. These are separate categories in the registry record; the counts should not be added to create a total because the record does not establish whether the groups overlap. The figures describe events recorded in this study group and do not provide a comparison with another treatment.
The listed serious adverse-event terms include Pneumonia at 2.9%, Cardiac failure congestive at 1.0%, Peritonsillar abscess at 1.0%, Prothrombin time prolonged at 1.0%, Lung neoplasm malignant at 1.0%, and Organising pneumonia at 1.0%. The registry record does not give the denominator or further details for these term-level percentages, so they should be read as recorded rather than recalculated or interpreted as comparative rates.
The deaths entry is not reported in the registry record. The adverse-event figures alone do not establish whether an event was caused by treatment, how long participants were followed for safety, or how events were defined and collected. The registry record also does not provide a control group against which to compare the safety counts.
12. What the Result Does, and Does Not, Mean
The record describes a completed, multicenter Phase 3 study of intravenous azithromycin followed by oral azithromycin in Japanese adults with community acquired pneumonia requiring initial intravenous therapy. It identifies a primary clinical response endpoint, the assessment source, the endpoint timeframe, and the analysis population. It also reports adverse-event counts for the single study group.
However, the primary response-rate estimate and its 95% confidence interval are not reported in the registry record. The record also does not report numerical findings for the secondary outcomes. Without those values, the clinical outcome cannot be characterized by magnitude or precision. The endpoint definition is not a substitute for the endpoint result, and the study completion status does not itself establish what the results were.
The single-group, non-randomized design is another important boundary on interpretation. An outcome proportion in the treated group does not indicate what would have occurred in a comparison group, and it does not isolate the treatment’s causal contribution. The open-label design may also matter for assessments involving clinical judgment; further information about masking of assessors is not reported in the registry record.
The findings that are available should be kept descriptive. Enrollment was 102, and safety information includes 8 affected by serious adverse events and 33 affected by other adverse events among 102 at risk. The recorded serious-event terms include pneumonia and other listed terms, but the registry does not establish causation or offer a control-group comparison. The deaths entry is not reported in the registry record.
In short, this record conveys how the study was designed and what it intended to measure, along with some safety counts. It does not provide the primary outcome estimate needed to describe clinical response, nor the comparative evidence needed to attribute an outcome to treatment. No conclusion about treatment effectiveness should be drawn from the design description or the missing endpoint result.
13. Why This Trial Matters Statistically
This trial is statistically instructive because its design and outcome definitions can be understood even though the primary numerical result is not reported in the registry record. The distinction between an endpoint specification and an endpoint estimate is fundamental: knowing how a response rate was defined does not reveal the observed response rate, and naming a confidence interval does not reveal its precision.
The study also illustrates the limits of interpreting a percentage from a single group. A response percentage may summarize what happened among participants meeting the analysis criteria, but it does not supply a controlled treatment contrast. Non-randomized allocation, no comparator arm, and open-label conduct shape what conclusions can be supported, regardless of the study’s Phase 3 designation.
Population definitions matter as well. The clinical per protocol set excludes participants who did not meet specified treatment, protocol, or evaluation criteria, while the endpoint definition excludes indeterminate assessments from its denominator. Those rules help define the target of the estimate, but the registry does not report the analysis-set size or category counts. Without them, the extent and consequences of exclusions cannot be assessed.
Finally, the record separates efficacy questions from safety description. It lists adverse-event counts and serious-event terms, but offers no comparative safety group and no reported death count. These data can be read as study-specific observations, not as evidence of causal attribution or a comparative risk difference. The trial therefore offers useful examples of how design, endpoint construction, population selection, missing-data handling, and reporting completeness govern statistical interpretation.
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 for interpretation is that the primary response-rate estimate and its confidence interval are not reported in the registry record. Numerical results for the secondary outcomes are also not reported. Without these results, the planned clinical and bacteriological outcomes cannot be quantitatively evaluated from the posted information.
The study has no randomized comparator and uses a single-group design. This prevents a direct estimate of treatment differences and limits causal interpretation. Its non-randomized, open-label conduct also leaves potential for differences in participant selection and assessment. The registry record does not report whether outcome assessors were masked or describe safeguards for clinical judgment.
The primary analysis population is defined by per protocol criteria, but its size is not reported. The response-rate denominator excludes indeterminate assessments, and the record does not report the number of effective, ineffective, indeterminate, or missing assessments. Although no imputation was used, further details about missing-data handling and sensitivity analyses are not reported in the registry record.
The registry lists five outcome measures and no analyses. It does not report a statistical testing hierarchy, multiplicity adjustment, confidence-interval calculation method, or the trial’s sample-size justification. These omissions limit assessment of planned inference and the interpretation of any hypothetical planning illustrations.
Safety interpretation is also constrained: the record provides single-group counts and listed serious-event terms, but no comparator, no reported death count, and no information sufficient to establish causality. These limitations concern what can be concluded from the registry record; they do not show that unreported procedures or results were absent from the full study documentation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Study Of Azithromycin Switch Therapy For Treatment Of Community Acquired Pneumonia (CAP) — NCT00809328.
- Registry record last updated 2011-05-19; status last verified 2011-05.
- Results first posted 2011-04-13.
- 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
NCT00809328 is a completed, multicenter, Phase 3, non-randomized, open-label, single-group study of azithromycin switch therapy for community acquired pneumonia. The official title describes Japanese adult subjects requiring initial intravenous therapy, followed by oral azithromycin. Enrollment was 102; the study start was 2009-02 and primary completion was 2010-03.
The primary outcome was clinical response assessed by a Data Review Committee, expressed as a percentage with a 95% Confidence Interval at End of Treatment, Day 15 and Day 29. The clinical per protocol population and response-rate denominator are defined in the registry, but the primary estimate and confidence interval are not reported in the registry record. Four secondary measures are listed, with no numerical results reported.
The registry lists 8 participants affected by serious adverse events and 33 affected by other adverse events among 102 at risk. The deaths entry is not reported in the registry record. The absence of a comparator means the study provides no randomized treatment contrast.