Occurrence of Potential Bacterial and Viral Pathogens in Stable Chronic Obstructive Pulmonary Disease and During Acute Exacerbations of the Disease, in Asia Pacific: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Occurrence of Potential Bacterial and Viral Pathogens in Stable Chronic Obstructive Pulmonary Disease and During Acute Exacerbations of the Disease, in Asia Pacific (NCT03151395), a na na study. The primary outcome is Percentage of Sputum Samples Positive for Bacterial Pathogens as Identified by Bacteriological Methods, in Any Stable COPD Patients and During AECOPDs.

2. Clinical Question

The study is concerned with pathogen occurrence in sputum, not with comparing the effect of treatments. Its stated motivation is that the infectious causes of exacerbations may vary by geographical region. The planned work focuses on the Asia Pacific region and also includes objectives related to exacerbation frequency, severity and duration, health-related quality of life, healthcare use and lung function.

The primary measure is sample-based: it counts positive sputum samples relative to visits at which a sample for the pathogen was tested. It therefore describes positivity among tested samples, not the proportion of participants who ever had a positive result. The registry record does not report the primary outcome estimates, the country-specific results or the number of tested samples contributing to each estimate. Those omissions limit what can be concluded about pathogen occurrence from the record alone.

3. Trial Design

The registry describes a completed, single-group study sponsored by GlaxoSmithKline, with enrollment of 197. The listed condition is respiratory disorders, and the participant group is further described as people with moderate to very severe COPD who had at least 1 documented moderate or severe acute exacerbation in the year before enrolment. Participants had sputum and blood collected at specified visits. The listed intervention is specimen sampling rather than a treatment assignment.

The study is not a randomized comparison: allocation is listed as NA, masking is none, and the model is single group. Stable visits and visits during acute exacerbations are two clinical circumstances for collecting and classifying samples, not separate randomized arms. A within-person comparison across these circumstances would still require care in interpretation, because the registry record does not describe a control group or an analysis that adjusts for repeated observations.

The primary outcome covers the period from Month 0 to Month 12, described as one year from the study start. A confirmed stable visit is defined as a scheduled study visit at which the investigator confirms the participant is stable or has recovered from a previous exacerbation. The record describes bacteriological methods for the primary outcome and includes other outcomes using PCR and bacteriological methods.

The registry lists a start date of 2017-08-25, primary completion on 2020-04-06 and a completed status. It also lists 20 outcome measures. The record does not report the countries, visit schedule details, recruitment flow or reasons for discontinuation. The phase is listed as NA, which is consistent with the record describing specimen collection rather than a therapeutic drug trial. Further protocol details, including the rationale for the enrollment target and any interim analyses, 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Analysis was performed on the Full Analysis Set which included all screened subjects who were enrolled except for those subjects who discontinued the study at Month 0 visit.

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 Percentage of Sputum Samples Positive for Bacterial Pathogens as Identified by Bacteriological Methods, in Any Stable COPD Patients and During AECOPDs, measured over Over the course of one year from the study start (Month 0 to Month 12).

The primary endpoint is the percentage of sputum samples positive for specified bacterial pathogens by bacteriological methods, considered across confirmed stable COPD visits and visits during acute exacerbations. The numerator is the number of samples positive for a particular pathogen; the denominator is the number of visits with a sputum sample tested for that pathogen. The registry specifies that the percentage is accompanied by a 95% confidence interval.

This sample-based measure addresses how often a pathogen is detected in the collected and tested specimens. It does not directly measure the percentage of participants with infection, nor does a positive sample alone establish that the detected organism caused an exacerbation. Results can also depend on which visits produced a usable sample and which tests were performed. The registry record does not give the actual percentages, confidence intervals or pathogen-specific denominators.

Reporting a confidence interval alongside a percentage is useful because an estimate from collected samples has sampling uncertainty. A narrower interval generally indicates greater precision under the method used; a wider interval indicates less precision. The interval does not by itself account for every possible source of bias, such as selective availability of samples or similarities among repeated samples from the same participant. The registry record does not report the numerical primary endpoint results or enough analysis detail to assess how those issues were handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a proportion. For each pathogen, the study description defines the numerator as positive sputum samples and the denominator as visits at which a sample for that pathogen was tested. The result is expressed as a percentage and paired with a 95% confidence interval. This is a natural descriptive form for a question about how often a test detects a pathogen in collected samples. It is not a participant-level risk unless each participant contributes exactly one relevant sample, which is not stated.

What does a confidence interval convey?

In general, a confidence interval conveys the uncertainty of an estimate under the statistical method used. A 95% confidence interval is constructed by a procedure intended, over repeated comparable sampling, to contain the underlying quantity at the stated rate. It is not a statement that there is a 95% probability that a fixed parameter lies in this particular interval. Precision depends on the number and pattern of observations as well as the method. Since the registry record supplies neither the primary estimates nor their intervals, their width and implications cannot be evaluated.

Why do repeated samples matter?

The endpoint is defined at the sample and visit level, and participants may have multiple scheduled visits. General statistical guidance is that repeated observations from the same person may be correlated. If they are, methods that account for within-person dependence can produce more appropriate uncertainty estimates than methods that treat every sample as independent. No repeated-measures model or other approach to within-person dependence is described in the registry record. The number of participants alone cannot substitute for the number of tested samples or explain their dependence.

Another general issue is over-dispersion. For count or binary data, over-dispersion means that variability is greater than a simple model assumes. It can arise for several reasons, including heterogeneity between participants or dependence among repeated observations. When present, ignoring it can understate uncertainty. This is a general consideration for repeated pathogen measurements, not a claim that over-dispersion occurred in this study. The registry record does not report whether it was assessed or how it was addressed.

How should the visit categories be understood?

The stable-visit definition depends on the investigator confirming that the participant is stable or has recovered from a previous exacerbation. The other clinical circumstance is an acute exacerbation visit. These categories describe the timing and status of sample collection. They do not represent randomized exposure groups. A difference in detected pathogens across categories would be descriptive unless an analysis and design justified a stronger interpretation. The registry record does not give the specific model, adjustment variables or comparison procedure used.

The record lists several detection approaches. The primary endpoint uses bacteriological methods. Other outcome descriptions include PCR for bacterial and viral pathogens and bacteriological identification of bacteria. These methods define different outcome measurements; results from one method should not be assumed to be interchangeable with another. The record does not provide enough information to assess test performance, handling of inconclusive tests or consistency between methods.

The sample-size assumptions describe a planning illustration based on an observed effect, using 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. This is not the stated design of this single-group study, and it must not be read as the study's own design or as observed power. For non-time-to-event illustrations, the stated convention is participants per arm; for time-to-event illustrations, it is the total number of events. The registry record does not report that these assumptions were used to plan enrollment.

General sample-size illustrations answer a conditional question: what sample size would be needed under specified assumptions to detect a chosen effect with a chosen power? They do not change the study design, demonstrate that an effect exists, or quantify the certainty of the posted results. Since the record does not report primary estimates or analysis details, such calculations cannot fill the gap in the outcome reporting. The statistical methods used for the primary endpoint beyond calculation of a percentage and 95% confidence interval are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 outcome measures, including bacterial and viral pathogen outcomes, measurements using both PCR and bacteriological methods, and classifications by COPD grade or exacerbation severity. Considering many outcomes can raise a multiplicity issue: the more estimates or statistical tests examined, the greater the chance that some findings may appear notable by chance. This is a general statistical concern, not evidence that any particular result is spurious. The registry record does not report whether multiplicity was addressed, whether any outcomes were prioritized beyond the stated primary outcome, or whether inferential tests were performed.

The primary outcome description specifies percentages and 95% confidence intervals, but the registry record does not report their numerical values. It also does not report pathogen-specific denominators, counts of missing or unusable samples, or reasons why a sample might be unavailable. Missing specimens can affect which observations contribute to a percentage. If availability is related to participants' condition or visit circumstances, the measured sample may not represent all intended visits. The record does not describe imputation, a missing-data sensitivity analysis or other handling procedures; these details are not reported in the registry record.

The stated analysis population is the Full Analysis Set. It includes all screened subjects who were enrolled except those who discontinued the study at the Month 0 visit. This definition identifies who was intended to contribute to the primary analysis, but it does not specify which participants had an evaluable sample for each pathogen or visit. It also does not explain how exclusions, later discontinuations or incomplete follow-up affected each endpoint. Enrollment of 197 therefore should not be taken as the denominator for every sample-based result.

The record does not report an analysis plan, adjustment strategy, interim analyses or a sample-size justification for the study itself. These omissions prevent an assessment of whether outcomes were analyzed as originally planned and how missing observations or multiple comparisons were handled.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pneumonia necrotizing (0.5%).

The safety record lists 197 people at risk in the Total Group, with 1 affected for serious adverse events and 1 affected for other adverse events. It also lists 2 deaths. The most frequent serious adverse event term displayed is necrotizing pneumonia, reported as 0.5%. These entries describe the safety reporting in the registry; they do not establish that an event was caused by the study procedures.

The listed intervention is sputum and blood sampling, rather than a therapeutic treatment. The adverse-event figures should therefore be read as events recorded among participants in the study, not as a comparison of treatment-related risks. The record does not provide enough detail to determine timing, event narratives, participant overlap between categories or attribution. In particular, the counts do not show whether the people listed in different categories were the same individuals.

Serious adverse events, other adverse events and deaths are distinct reporting categories. The entries should not be added together or interpreted as mutually exclusive totals. The reported 0.5% for necrotizing pneumonia is a registry value; no recalculation or causal interpretation is warranted from the record alone. Further details about event ascertainment and attribution are not reported in the registry record.

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

The study design addresses a descriptive question: which bacterial and viral pathogens are found in sputum collected from people with COPD at stable visits and during acute exacerbations. Its emphasis on the Asia Pacific region reflects the stated concern that infectious causes of exacerbations may vary geographically. The registry also describes objectives relating to exacerbation characteristics, quality of life, healthcare use and lung function. These objectives establish the scope of the study, not its findings.

The primary endpoint would quantify positivity among samples tested by bacteriological methods. If numerical results were available, they could describe the frequency of detection in the sampled visits and the precision of those estimates. The registry record does not report those numerical results. It therefore does not support a conclusion about the most commonly detected pathogen, a difference between stable and exacerbation visits, or the size and precision of any such difference.

Even with reported estimates, a sample-positive percentage would not prove that a detected organism caused an exacerbation. Detection is not the same as causation, and a single-group study without a control group does not establish what would have happened under a different condition. Comparisons between visit types would also need to account for repeated samples and differences in which visits yielded tested specimens. The analysis methods needed to assess those issues are not reported in the registry record.

The record does not show whether findings differ across countries, whether PCR and bacteriological methods produce consistent results, or whether pathogen patterns vary by COPD grade or exacerbation severity. Those topics appear in the outcome descriptions, but outcome descriptions alone do not demonstrate results. The study enrollment total likewise cannot tell how many observations contributed to each analysis.

Accordingly, the registry record is useful for identifying the intended population, sampling approach and outcome definitions, but the posted information is insufficient to judge the observed pathogen patterns or their uncertainty. No treatment effect should be inferred from this single-group sampling study, and planning illustrations based on an observed effect are not substitutes for outcome estimates or evidence of observed power.

13. Why This Trial Matters Statistically

This study illustrates why the unit of analysis matters in clinical research. The primary endpoint is based on sputum samples collected at visits, whereas enrollment counts people. A participant may contribute more than one sample, so these quantities answer different questions. Clear reporting of sample denominators and the number of participants contributing repeated observations is important for understanding both the estimate and its uncertainty.

It also illustrates the distinction between a descriptive study and a controlled comparison. Stable visits and exacerbation visits provide different contexts for observing pathogen detection, but the registry describes a single group and no randomized allocation. Any contrast between those contexts would describe observed patterns; it would not by itself establish causation. This distinction is especially important when a study's topic involves potential causes of a clinical event.

The endpoint definition is specific about its numerator, denominator, detection method and confidence interval. That specificity helps readers understand what a result would represent. Yet without the numerical estimates, confidence intervals and tested-sample counts, readers cannot assess magnitude, precision or the degree to which the samples reflect the intended visits. Outcome definitions and result reporting are complementary, not interchangeable.

The record also lists multiple outcomes spanning pathogen classes, laboratory methods and clinical subgroups. This breadth can support a fuller description when results and analysis methods are available, while also making transparent handling of multiple comparisons important. The registry does not report whether such handling was planned or performed.

Finally, the sample-size assumptions are framed as a planning illustration based on an observed effect, with a two-arm allocation framework unlike the listed single-group design. Keeping illustrative calculations separate from the actual design prevents readers from mistaking hypothetical planning values for trial characteristics or evidence about the results. The record's value is therefore chiefly in defining the measurement questions and highlighting what outcome and analysis details are needed for sound 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 important limitation for interpreting the registry record is that it does not report the numerical primary endpoint results. Pathogen-specific percentages, confidence intervals and tested-sample denominators are absent, so neither the pattern of detection nor its precision can be assessed. The record also does not provide numerical results for its listed secondary outcomes.

The study is single group, with no randomized comparator. Stable and exacerbation visits are not assigned comparison arms, and pathogen detection in a sample cannot establish that the organism caused an exacerbation. The record does not describe a method for adjusting comparisons between visit circumstances or for accounting for repeated measurements from the same participant. Those methods are not reported in the registry record.

The participant group is restricted to people with moderate to very severe COPD and at least 1 documented moderate or severe exacerbation in the year before enrolment. Findings from such a group would not automatically represent people with milder COPD, people without a recent qualifying exacerbation or populations outside the study setting. Although the study is described as taking place in several Asia Pacific countries, the countries and their respective contributions are not reported in the registry record.

Additional details needed to assess the evidence include sample availability by visit and pathogen, handling of missing or unusable samples, laboratory procedures, analysis methods, multiplicity handling and the rationale for enrollment. These are not reported in the registry record. The listed serious adverse event and death figures also lack detail on timing and attribution, so they cannot establish whether an event was related to sampling.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Occurrence of Potential Bacterial and Viral Pathogens in Stable Chronic Obstructive Pulmonary Disease and During Acute Exacerbations of the Disease, in Asia Pacific — NCT03151395.
• Registry record last updated 2021-06-14; status last verified 2021-05.
• Results first posted 2021-06-14.
• 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

The registry describes a completed, single-group study of pathogen occurrence in people with moderate to very severe COPD who had a documented recent moderate or severe exacerbation. Enrollment was 197, and sputum and blood sampling was the listed intervention. The primary outcome was the percentage of sputum samples positive for specified bacterial pathogens by bacteriological methods, across confirmed stable visits and acute exacerbation visits during Month 0 to Month 12.

The record lists 20 outcome measures and describes other bacterial and viral assessments using PCR and bacteriological methods. It does not report numerical primary or secondary outcome estimates, pathogen-specific denominators or detailed analysis methods. The record also lists 1 participant affected by a serious adverse event, 1 by another adverse event, 2 deaths and necrotizing pneumonia at 0.5% as the top serious adverse event term. These safety entries do not establish causation. The available information defines the study questions and population, but does not permit assessment of pathogen frequencies or their precision.