Impact of Two Alternative Dosing Strategies for Trachoma Control in Niger: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Two Alternative Dosing Strategies for Trachoma Control in Niger (NCT00618449), a randomized phase 4 study. The primary outcome is Infection With Chlamydia Trachomatis Diagnosed by Use of NAATs [Nucleic Acid Amplification Test].

2. Clinical Question

The clinical question is framed around a community-level treatment strategy rather than an individual treatment comparison alone. The intended comparison concerns whether a repeat community-wide treatment changes infection and trachoma at follow-up. The registry’s primary outcome title specifically identifies infection with Chlamydia trachomatis diagnosed by NAATs, while the trial summary also names trachoma as a target of the hypothesis. The record does not give a numerical result for either endpoint, so the direction and magnitude of any difference between strategies cannot be described.

The outcome description specifies participants and a per-protocol population. It does not define the threshold or laboratory criteria used to classify a participant as infected, nor does it give the number assessed at follow-up. Details about the clinical definition of trachoma, the timing of examinations beyond the stated primary timeframe, and how participants were selected for the per-protocol analysis are not reported in the registry record.

3. Trial Design

The study is identified as a randomized, single-masked, parallel trial in Phase 4. Its enrollment is 1139. It is listed as completed, with a start date of 2008-01 and primary completion date of 2009-05. The sponsor is the University of California, San Francisco. The listed conditions are trachoma and Chlamydia trachomatis.

The registry describes the study as community based and conducted in the Maradi region of Niger. The treatment strategies are community-wide azithromycin dosing: two treatments spaced one month apart compared with a single mass treatment. The arm descriptions refer to villages assigned to treatment arms, which indicates that village residence is relevant to how treatment assignment was organized. The number of villages, the randomization procedure, and whether the analysis accounted for grouping of participants within villages are not reported in the registry record.

Single masking means that the record identifies masking of one party, but it does not say which party was masked or how masking was maintained. The parallel model indicates that the treatment groups were compared as separate groups rather than through a crossover design. The registry does not provide further details about allocation concealment, treatment adherence, follow-up procedures, or crossover between assigned strategies.

The brief summary describes an intention to compare infection and trachoma at one year. The primary outcome timeframe is stated as one-year post-treatment. The record does not clarify the exact visit window or whether all outcome assessments occurred at the same interval for both strategies. The arm descriptions are incomplete, so the full administration schedule cannot be reconstructed from the record alone. Although the trial is marked completed, that status does not by itself supply outcome findings or establish how many participants completed follow-up.

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: Per protocol.

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 Infection With Chlamydia Trachomatis Diagnosed by Use of NAATs [Nucleic Acid Amplification Test], measured over 1-year post-treatment.

The registered primary endpoint is infection with Chlamydia trachomatis diagnosed using nucleic acid amplification tests, at one-year post-treatment. The outcome unit is participants, and its stated analysis population is per protocol. This is a binary endpoint in the registry’s outcome classification: participants are counted according to whether infection is identified. The registry describes the outcome parameter as a number of participants with an event.

A NAAT is a laboratory method that detects genetic material from an organism. In general, a laboratory-based infection endpoint can provide a defined way to classify infection at the assessment time, rather than relying only on clinical signs. Trachoma is also named in the trial’s stated research hypothesis, but the primary outcome title specifically identifies laboratory-diagnosed infection. The record does not report the assay details, positivity criteria, or the number of participants with a positive test.

Using an endpoint at one-year post-treatment is intended to assess infection at a follow-up time after the community treatment strategy has been delivered. It does not, by itself, describe the timing of infection between treatment and assessment or establish the cause of an infection detected at follow-up. The result would need to be interpreted with the group counts, analysis population, follow-up completeness, and statistical comparison. Those outcome results and details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods that can be identified from the registry are randomized allocation, single masking, a parallel design, and a primary outcome classified as binary. These labels describe broad elements of the design, not the complete statistical analysis plan. Random allocation is intended, in general, to make treatment groups comparable on average with respect to measured and unmeasured characteristics. It does not guarantee that groups will be identical, particularly when treatment assignment occurs through communities. The registry does not describe the sequence generation method, allocation concealment, or number of villages.

What does random allocation contribute?

In general, randomization supports a causal comparison by separating assignment from investigators’ or participants’ choice of strategy. Its validity depends on carrying out the assigned procedure as planned and analyzing participants in a way that respects how randomization occurred. The arm descriptions refer to villages assigned to treatment groups, so the assignment may involve groups of residents rather than independent individual assignments. The number and size of those groups and the exact randomization unit are not reported in the registry record.

When participants within the same village may have more similar outcomes than participants in different villages, their observations are statistically related. In general, an analysis that treats every participant as fully independent can understate uncertainty if assignment and outcomes are clustered. Appropriate methods can account for such dependence, but the method used in this trial is not reported in the registry record. It is also not possible to assess how much clustering matters without details about the number of villages and outcome data.

How should the binary endpoint be understood?

A binary endpoint classifies each assessed participant into an event or no-event category. Here, the event is infection diagnosed by NAATs at one-year post-treatment, and the record describes the outcome as a count of participants. In general, a treatment comparison for a binary outcome can be expressed through group risks, a risk difference, a relative measure, or another specified contrast. Each measure answers a different question about the relationship between treatment strategy and outcome. The registry does not report event counts, denominators at follow-up, or an effect estimate, so none of these comparisons can be interpreted from the record.

For an outcome count to be interpretable as a group rate or risk, the number of participants assessed must be known as well as the number with the event. The enrollment total does not establish the follow-up denominator, especially when the stated analysis population is per protocol. The registry does not report the number excluded from that population or the reasons for exclusion. It also does not give the infection definition or laboratory decision rule.

What do masking and the parallel design tell the reader?

Single masking indicates that one party was intended to be unaware of treatment assignment, but the masked party is not named. In general, masking can reduce the influence of treatment knowledge on assessment or behavior, depending on who is masked and how the procedure is implemented. The registry record does not explain these details. A parallel design means each group follows its assigned treatment strategy and the groups are compared, rather than participants switching between strategies. The record does not give adherence or crossover information.

The trial’s community setting matters to both interpretation and analysis. The treatment strategies are applied community-wide, and the arm descriptions state that villages were assigned. In general, individual outcomes can be affected by exposure to other residents’ treatment and infection status. Such community effects may be part of the strategy being evaluated, rather than a nuisance that can simply be ignored. How community transmission, treatment coverage, and village-level dependence were handled analytically is not reported in the registry record.

What can be said about statistical testing and precision?

The registry includes general assumptions for planning illustrations: a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These assumptions describe planning illustrations, not a reported design justification or observed treatment result. The numerical sample-size scenarios are not included in the record summarized for this trial. The effect estimate on which such illustrations depend is also not reported, so the illustrations cannot be independently interpreted from the available trial entry.

In general, a significance level is a rule for calibrating a statistical test under its assumptions. Equal allocation is a planning assumption about the intended division between groups, and a normal approximation is a way of approximating a sampling distribution. These choices do not establish that the trial used that exact analysis for its primary endpoint. The registry does not report the test, model, covariate adjustment, confidence-interval method, or any prespecified statistical plan.

In general, over-dispersion occurs when observed variability is greater than a statistical model expects. For clustered community data, within-village similarity can create greater uncertainty than a model based on independent participants would suggest. Methods that account for clustering or over-dispersion can produce more realistic standard errors and intervals. Whether the trial used such methods is not reported in the registry record, so no particular model should be attributed to this analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry does not report how multiplicity was handled. The trial summary names both ocular Chlamydia trachomatis infection and trachoma as outcomes of interest, while the registered primary outcome title concerns laboratory-diagnosed infection. The record also flags that the primary outcome has several categories or time points and was not reduced to one comparison. The timing and definitions of any additional endpoint categories, and whether any adjustment was planned for multiple comparisons, are not reported in the registry record.

In general, testing several outcomes, time points, or subgroup comparisons can increase the chance of observing a seemingly notable result by chance. A statistical plan may identify a primary contrast in advance or use an adjustment approach when multiple comparisons are central. The registry information does not establish which approach, if any, was planned or used. The record lists zero analyses, so it does not provide statistical results that would allow the multiplicity strategy to be evaluated.

The primary outcome population is described as per protocol. The registry does not define the per-protocol criteria, state how deviations were handled, or report an intention-to-treat analysis. It also does not report the number of participants with missing outcome data, reasons for missingness, or a method for handling missing observations. These details matter because the available outcome data may not represent all randomized participants if follow-up is incomplete or inclusion in the analysis depends on post-randomization events.

In general, missing-data methods rely on assumptions about why data are absent. Complete-case analysis, imputation, and sensitivity analyses address missingness in different ways and can lead to different estimates. No such method or sensitivity analysis is reported in the registry record. Without follow-up counts and an explicit analysis population, the completeness and representativeness of the endpoint data cannot be assessed.

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 5% reporting threshold.

The adverse-event entries list the two-dose azithromycin group with 581 participants at risk for serious adverse events and 0 affected. The single-dose group lists 558 at risk and 0 affected. The other adverse-event entries list the same at-risk group sizes and 0 affected in each group. These are the counts recorded in the registry; they are not an estimate of comparative risk or evidence about events outside the recorded observation and reporting process.

The record does not define the serious-event criteria, explain the period over which events were collected, or give further details about ascertainment. It lists no top serious-event terms. Death counts are null, so deaths are not reported in the registry record; a null entry should not be read as a recorded count of zero. The record also does not report adverse-event analyses, event severity apart from the serious-event grouping, or an assessment of differences between groups.

In general, a zero count in a registry field means that no events are entered for that group in that field; it does not establish that risk is absent. The number at risk gives context for the reported count, but interpretation also depends on follow-up duration, completeness, and consistent event surveillance. Those details are not reported in the registry record. The entries therefore support only a narrow description of the counts as posted, not a broad conclusion about safety.

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

The record establishes that a randomized, single-masked, parallel community trial was conducted to compare two community-wide azithromycin dosing strategies in Niger. It identifies a primary infection endpoint based on NAAT diagnosis at one-year post-treatment and specifies a per-protocol analysis population. It also records serious and other adverse-event counts for each group. These are useful descriptions of the trial question and selected registry entries.

The record does not report the primary infection counts, group denominators at follow-up, treatment effect, confidence interval, or p-value. It therefore does not show how the groups differed on the primary endpoint or how precise that comparison was. The stated hypothesis is not a result, and the completed status is not a substitute for findings. No conclusion about whether either dosing strategy reduced infection or trachoma can be drawn from the registry information available.

Even if outcome counts were available, a single assessment at one-year post-treatment would describe infection status at that assessment rather than the full course of infection over time. The registry does not report interim outcome assessments, reinfection patterns, or the duration of protection. It also does not provide the data needed to distinguish the effect of the treatment schedule from differences in implementation, adherence, or follow-up.

The safety fields record zero affected participants in the listed serious and other adverse-event categories, but provide no event definitions, collection details, or death counts. These entries do not establish that no adverse events occurred outside the recorded categories or observation period. Nor do they provide a formal comparison of safety between treatment groups.

In general, trial evidence is interpreted by considering the design, endpoint definition, analysis population, effect estimate, uncertainty, and completeness of follow-up together. The registry contains enough information to describe the broad design and question, but not enough to assess the treatment effect or its precision. Any account of the trial’s comparative results would require outcome results and analysis details not reported in the registry record.

13. Why This Trial Matters Statistically

This trial raises statistical issues common to community-based infectious-disease research. The strategies were delivered community-wide, and the arm descriptions refer to villages assigned to treatment groups. Such designs can involve dependence among people living in the same community and can make the community, rather than the individual alone, central to the comparison. The registry does not report the number of villages or the methods used to account for that structure, leaving an important part of the statistical interpretation unresolved.

The primary endpoint is a laboratory-diagnosed infection measure at a stated follow-up time. That gives the research question a defined biological outcome, distinct from the clinical condition named alongside it in the trial summary. It also illustrates why a registered endpoint must be distinguished from a hypothesis: the record identifies what was intended to be assessed but does not provide the observed result or the statistical contrast.

The stated per-protocol population highlights another important design issue. In general, excluding participants after randomization can affect the comparability created by random allocation, depending on the reasons for exclusion and how those reasons relate to outcomes. Without the per-protocol criteria, participant flow, and any additional analysis population, the impact cannot be assessed. Reporting both the endpoint denominator and the analysis approach is important for understanding what a treatment estimate represents.

Finally, the registry illustrates the distinction between trial completion and result reporting. A completed study can still have an incomplete public record for statistical interpretation. With no outcome analysis, effect estimate, or interval, neither the magnitude nor precision of the comparison can be evaluated. The statistical importance of this record lies in recognizing both the community-level design questions it raises and the limits imposed by missing results.

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 principal limitation of the registry record for interpreting this trial is that it does not report the primary outcome results. There are no group-specific infection counts, follow-up denominators, comparative estimates, confidence intervals, or test results. The record therefore cannot support a statistical assessment of the primary treatment contrast. Its completed status does not resolve this gap.

The registered analysis population is per protocol, but the criteria for inclusion in that population and the number of participants meeting them are not reported. Participant flow after enrollment, missing outcome data, reasons for loss to follow-up, and methods for handling missingness are also not reported in the registry record. Without those details, it is not possible to assess whether the analyzed participants represent the randomized population.

The community-based design and village assignment described in the arm text raise questions about clustering and the unit of randomization. The number of villages, randomization procedure, and statistical adjustment for within-village dependence are not reported. These details are material because the precision of a community-level comparison can depend on the number of independently assigned communities and on similarities among residents.

The single-masking label does not identify who was masked or how masking was implemented. The arm descriptions are truncated, and do not fully document treatment delivery or adherence. The registry also does not give laboratory criteria for NAAT positivity, the definition of trachoma, or the precise follow-up window. Details of multiplicity, interim analyses, covariate adjustment, and the statistical plan are not reported in the registry record.

The adverse-event entries lack definitions, collection procedures, and death counts. The registry lists zero affected participants in its serious and other event fields, but this does not provide a full safety assessment. Taken together, these omissions limit evaluation of both the outcome results and the methods that would be needed to interpret them.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Impact of Two Alternative Dosing Strategies for Trachoma Control in Niger — NCT00618449.
• Registry record last updated 2012-05-08; status last verified 2012-04.
• Results first posted 2012-05-08.
• 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

NCT00618449 is a completed Phase 4 randomized, single-masked, parallel community-based trial sponsored by the University of California, San Francisco. It enrolled 1139 participants in the Maradi region of Niger and compared community azithromycin dosing strategies: two community-wide treatments spaced one month apart and a single mass treatment.

The registered primary outcome is infection with Chlamydia trachomatis diagnosed by NAATs at one-year post-treatment, in a per-protocol population. The registry record lists one outcome measure and zero analyses, and does not report primary outcome results or a treatment-effect estimate. Adverse-event entries list 0 affected among 581 at risk in the two-dose group and 0 among 558 at risk in the single-dose group; death counts are not reported in the registry record. Details of the statistical analysis plan, missing-data handling, and village-level analysis are also not reported.