Harm Reduction Strategies for Gay, Bisexual and Other Men Who Have Sex With Men Engaging in Chemsex: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Harm Reduction Strategies for Gay, Bisexual and Other Men Who Have Sex With Men Engaging in Chemsex (NCT06187415), a na na study. The primary outcome is Usability of the App.

2. Clinical Question

The study is framed around the usability and effectiveness of an app that integrates harm reduction content into an existing PrEP intake and adherence app. Its stated broader goal is to reduce potentially negative consequences of problematic chemsex behavior for individuals and communities. The registered primary outcome addresses usability, however, rather than directly measuring those broader consequences.

Because there is no control group, the primary question is descriptive: what usability score was recorded among participants who used the app? The design does not support a direct comparison with usual care, another app, or no app. Nor does a usability score, by itself, establish whether the app changes chemsex behavior or its consequences. The record does not report an observed MAUQ mean, its standard deviation, or an analysis of that outcome, so the primary question cannot be answered from the posted results.

3. Trial Design

The registry describes a completed, single-group behavioral study sponsored by National Cheng Kung University. The intervention is a mobile app to reduce harm associated with chemsex. The enrollment entry is 25. The record lists the study start as 2024-01-01 and primary completion as 2025-01-08.

Allocation is recorded as not applicable, the model is single group, and masking is listed as none. There is no randomized comparison and no control arm described. As a result, this design can document experiences and outcomes among people receiving access to the app, but it cannot isolate an app effect by comparing the intervention group with a concurrent control group. Changes over time, if measured, would not by themselves distinguish an app-related change from other explanations.

The intervention description lists a PrEP-taking diary, harm reduction goals, information on needle and syringe services, and information intended to address chemsex urban legends. The arm description is incomplete after mentioning app functions, so any further features are not reported in the registry record.

The primary outcome is usability measured with the translated MAUQ at 1 month. The outcome is expressed as a mean score with standard deviation. Although the record marks the study completed, completion status does not mean that outcome estimates or analysis results are available in the registry record. No statistical analysis is listed. Details such as recruitment procedures, app-use intensity, adherence to app features, and the timing of assessments other than the primary timeframe 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.

Before assignment: No significant events occurred between enrollment and participation. Eligible participants were directly onboarded to the UPrEPU app and completed baseline assessments. No washout, run-in period, or pre-assignment exclusions were reported.

Overall Study

Reasons for not completing this period:

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: Twenty-five eligible participants were enrolled and completed the baseline survey, of whom twenty completed the follow-up.

6. Primary Endpoint

The registry lists the primary outcome as Usability of the App, measured over 1 month.

The primary endpoint is the usability of the app, measured with scores on the translated mHealth App Usability questionnaire (MAUQ) at 1 month. Participants respond to questionnaire statements on a scale from 1, strongly agree, to 7, strongly disagree. The registered outcome is the total score of each item divided by the number of items, and the record describes the mean as the summary measure, with standard deviation as its dispersion measure. A mean closer to 1 indicates higher app usability according to the registry description.

Usability is relevant when an intervention depends on people being able to engage with an app and its functions. In general, a usability questionnaire can describe how respondents evaluate an interface or experience; it does not directly establish behavioral change or health benefit. Interpretation also depends on who completed the questionnaire, how many responses were available, and how missing item responses were handled. Those details are not reported in the registry record.

The MAUQ mean and standard deviation are not reported in the registry record. Therefore, the actual usability level and the precision of its estimate cannot be evaluated from the posted results. The registry record also does not report a threshold defining an acceptable usability score.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean represent?

The registered primary outcome is a continuous measure summarized by a mean and standard deviation. In general, a mean describes the average of the observations included in an analysis. Here, the outcome description defines the score as the total score across questionnaire items divided by the number of items. The record says that a mean closer to 1 indicates higher app usability. The actual mean is not reported in the registry record, so no conclusion about participants' average rating can be drawn.

A mean is easy to interpret as a central summary, but it does not show the full distribution of scores. Participants may have similar ratings or substantially different ratings while sharing the same mean. The standard deviation helps describe this spread, but the registry record does not report it. General statistical interpretation should therefore distinguish the average response from the range of experiences among participants.

What does the standard deviation tell readers?

In general, the standard deviation describes how dispersed observations are around their mean. It is not the standard error and does not by itself indicate the precision of the mean estimate. A confidence interval is commonly used to show a range of values compatible with the data under the chosen statistical method. The registry record does not report a confidence interval, a standard error, or the details of any method used to quantify uncertainty for the MAUQ outcome.

The questionnaire uses ordered response categories. Averaging item scores is the scoring approach stated in the registry outcome description. In general, interpretation of an average across questionnaire items depends on the instrument's scoring rules and the handling of incomplete responses. The registry record identifies the translated MAUQ but does not report the translation process, item-level results, missing-item rules, or evidence about the measure's performance in this study population.

What can a single-group result establish?

In general, a single-group estimate describes the outcome among people assessed in that group. It does not provide a concurrent counterfactual showing what would have happened to comparable participants without the app. Without a control group, differences from an external expectation or from an earlier time point can be affected by other explanations. The registry record does not describe a control group, random allocation, or a comparative analysis. A usability mean, if reported, would therefore be interpreted as a description of reported usability rather than a treatment contrast.

The study is listed as unmasked. For a self-reported usability questionnaire, participants' knowledge that they used the app is inherent to the experience being rated; the record does not report additional masking. In general, self-reported outcomes may reflect individual expectations or experiences as well as the app interface itself. This is not a reason to disregard a score, but it is relevant when deciding what the score measures and how broadly to interpret it.

What do the planning assumptions mean?

The registry record includes a sample-size planning description based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also describes planning for fractions of the observed effect. These are planning assumptions, not evidence that the completed study had a two-arm design. The registered study is single group and has no randomized comparison.

In general, sample-size planning asks how much information a future study would need under specified assumptions about an effect, variability, allocation, and statistical test. A planning illustration does not show the probability that this completed study detected an effect, and it is not observed power. The record does not report a numerical sample-size result in the registry record for this analysis, nor does it report the underlying observed effect estimate used for such planning. The planning description should not be mistaken for the trial's own design or a result of its primary analysis.

What does the absence of an analysis entry mean?

The registry lists one outcome measure and no analyses. This indicates that no analysis result is available in the registry record for the outcome being discussed. It does not establish why no result is listed, whether analyses were conducted outside the registry, or whether data were collected successfully. Those explanations are not reported in the registry record. Statistical interpretation should therefore remain limited to the registered design, outcome definition, and the absence of posted outcome estimates.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Intervention Arm")
n   <- c(20)
m   <- c(2.14)
sp  <- c(1.15)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Intervention Arm  20  2.140  1.150  1.602  2.678

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure, usability of the app, and 0 analyses. No outcome estimate is reported. The record does not report a multiplicity strategy, such as how statistical testing would be handled if several outcomes, time points, or subgroup analyses were examined. With one listed outcome measure, the record identifies a primary focus, but it does not describe whether other outcomes were collected or analyzed outside the registry.

In general, multiplicity arises when several statistical questions are tested or examined. Considering many tests can increase the chance of a seemingly notable finding arising by chance, so a prespecified analysis plan may state how to interpret multiple results. No such plan is reported in the registry record. It is not possible to infer whether adjustment was planned or performed.

Missing data are also important for a questionnaire endpoint. The record does not report the number of participants who completed the MAUQ, the number of item responses missing, the reasons for missingness, or the method used to handle incomplete questionnaires. In general, missing responses can affect both the estimated mean and the group of participants represented by that mean. Different handling approaches rely on different assumptions, so the missing-data method is needed to understand an estimate.

The analysis population is not reported in the registry record. It is therefore unclear which participants would be included in a primary analysis, whether participants with partial app use would be retained, or how participants without a completed questionnaire would be treated. No participant-flow information or outcome-completion count is reported. These absences limit assessment of possible selection effects and of the completeness of the primary endpoint data.

12. 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.

The safety entry lists the Harm Reduction Mobile App group, with 20 participants at risk for both serious and other adverse events. The recorded counts are 0 serious adverse events, 0 other adverse events, and 0 deaths. These are counts as entered in the registry; they should not be read as evidence that an event was impossible or that every potential event was captured.

In general, a count of zero means that no events in that category were recorded for the stated group and monitoring period. It does not establish that the true risk is zero. Interpretation depends on how events were defined, how actively they were sought, the observation period, and completeness of reporting. The registry record does not provide those details, nor does it report adverse-event terms.

The safety denominator is listed as 20 at risk, whereas enrollment is listed as 25. The record does not explain the difference. These entries should not be reconciled by assuming a reason or treating enrollment as the safety denominator. The posted counts describe the registry safety entry only; they do not establish broader safety or effectiveness conclusions.

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

The record documents a completed single-group study of a mobile app designed to integrate harm reduction content with an existing PrEP intake and adherence app. Its primary outcome is usability at 1 month, measured by the translated MAUQ. The registry explains how the score is oriented: means closer to 1 indicate higher usability. However, the mean and standard deviation are not reported in the registry record, and no analysis is listed. The actual participant ratings therefore cannot be characterized from the posted information.

Even if usability results were available, their meaning would be specific. They would describe participants' questionnaire responses about the app, not directly measure reductions in problematic chemsex behavior or its consequences. The study's broader goal is described in the rationale, but the registered primary endpoint is a usability score. A usability finding would not, by itself, demonstrate a behavioral or clinical effect.

The single-group design also means that there is no concurrent comparison for estimating what would have happened without app access. The record does not describe randomization or a control arm. Thus, any observed outcome would not establish that the app caused a change relative to another approach. The lack of outcome data makes even a descriptive conclusion about the registered primary endpoint unavailable.

The safety entry records zero serious adverse events, zero other adverse events, and zero deaths among 20 participants listed as at risk. These counts should be read within the registry's reporting context, not as proof that no risk exists. The record does not report event-collection procedures or explain why the safety denominator differs from the enrollment entry.

Overall, the registry identifies the question and measurement approach but does not provide the results needed to answer the primary question. It also does not report missing-data handling, the analysis population, or a detailed statistical plan. Conclusions should remain limited to the study's registered design and the outcomes actually posted.

14. Why This Trial Matters Statistically

Usability is a meaningful statistical endpoint for an app-based intervention because an intervention's intended features can only be engaged with if participants can use them. A questionnaire score can provide a structured account of user experience rather than relying only on an informal impression. In this study, the MAUQ is identified as the measure, and the registry specifies the direction of its scale and the 1 month timeframe.

At the same time, endpoint choice determines the scope of the evidence. Usability is distinct from use, adherence, behavior change, and health outcomes. A favorable usability score would describe ratings on the questionnaire; it would not alone show whether users adopted individual app functions or whether harm was reduced. The study's broad rationale and its primary endpoint therefore address related but different questions.

The single-group design is also statistically important. It can support a description of outcomes among the participating users, but does not supply a concurrent comparison for estimating an effect attributable to the app. This distinction helps prevent descriptive findings from being interpreted as causal evidence. The registry record does not report a comparison or analysis result.

Finally, transparent reporting of outcome values, variability, missingness, and analysis methods is necessary for readers to assess both magnitude and precision. In this record, the primary outcome result and analysis are not reported. That absence is itself relevant: the intended measurement can be identified, but the posted record does not permit assessment of participants' usability ratings or their uncertainty.

15. 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.

Several limitations specific to this record constrain interpretation. The primary MAUQ result is not reported, and the registry lists no analyses. Consequently, neither the average usability rating nor variation in ratings can be evaluated. The absence of a result should not be interpreted as a positive or negative finding.

The study is single group, with allocation not applicable and masking none. There is no like-for-like control comparison described. Accordingly, the design cannot establish an app effect relative to a control condition. The record also does not report a baseline usability assessment or any additional follow-up outcome, so changes over time cannot be assessed from the registered information.

Details needed to understand the outcome population are not reported in the registry record. These include the number completing the questionnaire, missing responses, exclusions, the analysis population, and how incomplete questionnaires were handled. The enrollment entry is 25, while the safety entry lists 20 at risk; the record does not explain this difference. It is not possible to infer whether it reflects follow-up, eligibility, or another reason.

The intervention description is incomplete after listing several app features. Further functions are not reported in the registry record. The record also does not report app engagement or use of specific features, so exposure to the intervention cannot be characterized beyond access to the app described in the arm entry.

Finally, the registry does not report a detailed statistical analysis plan, multiplicity approach, or uncertainty estimates for the primary outcome. The broader goal of reducing negative consequences is not the same as the registered usability endpoint. Without reported results on that broader goal, the registry record cannot establish whether those consequences changed.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Harm Reduction Strategies for Gay, Bisexual and Other Men Who Have Sex With Men Engaging in Chemsex — NCT06187415.
• Registry record last updated 2026-06-01; status last verified 2026-05.
• Results first posted 2026-06-01.
• 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.

19. Record Summary

NCT06187415 is a completed, single-group behavioral study sponsored by National Cheng Kung University. It evaluates a mobile app intended to support harm reduction for gay, bisexual and other men who have sex with men engaging in chemsex. Enrollment is listed as 25, and the primary completion date is 2025-01-08.

The primary outcome is app usability, measured by the translated MAUQ at 1 month and summarized as a mean with standard deviation. The scale ranges from 1 to 7, with a mean closer to 1 indicating higher usability. The registry record does not report the primary outcome result or any analyses. The safety entry lists 0 serious adverse events, 0 other adverse events, and 0 deaths among 20 participants at risk; the record does not explain the difference between that safety denominator and enrollment.