Hepatitis C Pharmacy-based Strategy for Injectors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Hepatitis C Pharmacy-based Strategy for Injectors (NCT04698629), a registered phase not stated study. The primary outcome is Community Pharmacy Program Successful Linkage.

2. Clinical Question

The study concerns implementation and access, rather than a randomized test of one treatment against another. Its stated aim is to evaluate acceptability and use of a community-pharmacy care-delivery model for people who inject drugs with hepatitis C who need treatment. Navigators are part of the described pathway to the program.

The study summary also describes interest in hepatitis C treatment initiation, completion, and cure, as well as receipt of medications relevant to overdose prevention, HIV prevention, and opioid use disorders. Self-reported substance use and HIV risk behaviors are also mentioned. These objectives provide context for the pilot, but the primary question is narrower: whether participants link to the pharmacy program and attend its initial evaluation. The record does not report a comparative estimate of the program’s effect against another care pathway.

3. Trial Design

The registry identifies NCT04698629 as a completed pilot study sponsored by the University of Washington. The record lists enrollment of 40. The study start date is 2020-11-05, and the primary completion date is 2023-06-30. Its title describes a pharmacy-based strategy for people who inject drugs, while the official title describes a community-pharmacy model intended to expand access to medications related to hepatitis C, opioid use disorders, overdose, and HIV.

The described population is adults who test positive for hepatitis C at community sites and agree to linkage to the pharmacy program through patient navigators. The primary outcome is the number and percentage who successfully link to the program and are seen for an initial evaluation, assessed over 6 months. Initiation of hepatitis C treatment is listed as a secondary outcome. The summary also describes treatment completion and cure and other service-use and self-report outcomes.

The record identifies an observational group and explicitly notes that this is not a randomized comparison. Allocation is not stated, and the arms are not a like-for-like control comparison. Thus, the design information does not support interpreting the outcome as a randomized treatment contrast. The registry record does not report further details about the recruitment process, the number who completed follow-up, or how participants were assigned to any groups. It also does not report a statistical analysis plan or a sample-size justification. These omissions limit what can be inferred about the study’s intended comparisons and how the results were meant to be analyzed.

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:

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: Person who injects drugs, with documented positive hepatitis c virus test results.

6. Primary Endpoint

The registry lists the primary outcome as Community Pharmacy Program Successful Linkage, measured over 6 months.

The primary endpoint counts participants who both successfully link to the community-pharmacy program and are seen for an initial evaluation. Its timeframe is 6 months. The registry describes the outcome as a number and percentage, so the intended summary has a count component and a proportion component. The record does not report the observed count or percentage.

This endpoint is relevant to the study’s implementation question: whether people identified in community settings reach the pharmacy program and begin an evaluation there. It captures an early step in a care pathway, rather than a clinical outcome such as hepatitis C cure. A linkage measure can help describe whether a delivery model is being used, but the endpoint alone cannot establish why some participants link or do not link, whether the model caused linkage, or whether people who attend an initial evaluation complete subsequent care.

For a proportion to be interpreted, readers need to know which participants form its denominator and how missing follow-up is handled. Those analysis details are not reported in the registry record. Nor does the record post the primary endpoint result. Consequently, the endpoint’s definition is available, but its observed frequency and precision cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a participant count: the number who successfully link to the pharmacy program and attend an initial evaluation within 6 months. The record also describes the outcome as a percentage. In statistical terms, this is a binary outcome for each participant: the linkage criterion is either met or not met within the specified period. The group count is the number meeting the criterion; a percentage additionally requires a defined denominator.

What does a count or percentage describe?

As a general statistical explanation, a count records how many observed participants meet an outcome definition. A proportion places that count in relation to a defined group. The denominator might be all enrolled participants or a prespecified subset, depending on the analysis plan. These choices can lead to different interpretations, so the denominator and rules for participants with incomplete follow-up matter. The registry record does not report those rules or the primary outcome count. The enrollment figure should not be substituted for an endpoint denominator without a stated analysis definition.

How should uncertainty be assessed?

As a general statistical explanation, a confidence interval describes the range of values compatible with the observed data under a specified statistical method. For a binary outcome, its width depends on the observed proportion, the amount of information available, and the method used to calculate it. A point estimate alone does not communicate precision. No primary outcome estimate or confidence interval is reported in the registry record, and the method for any such interval is not reported. It is therefore not possible to assess the precision of linkage from the registry information.

What can an observational result establish?

In general, an observational group can describe what occurred among participants who received or encountered a program. A causal comparison requires a suitable counterfactual: evidence about what would have happened to comparable participants under an alternative. Random assignment is one approach to creating such a comparison, but the registry explicitly says this is not a randomized comparison and that allocation is not stated. The record also cautions that its arms are not a like-for-like control comparison. Consequently, a group’s observed linkage frequency, if reported, would not by itself identify a causal program effect.

What does the listed analysis information mean?

The registry lists 0 analyses. The statistical model, handling of repeated or incomplete observations, covariate adjustment, and approach to uncertainty are not reported in the registry record. No inferential results are posted. This means the record does not offer a basis for interpreting a p-value, adjusted effect, or model-based estimate for the primary outcome.

The record’s sample-size assumptions describe planning illustrations, not the trial’s own design. They use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. These assumptions should not be read as evidence that the pilot used those design choices. The illustrations are planning scenarios, not observed power, and the registry does not report a trial-specific sample-size justification. For time-to-event illustrations, the stated convention is a total event count; other illustrations use participants per arm. These conventions do not provide evidence of an actual randomized two-arm analysis in this study.

Why does over-dispersion matter in general?

Over-dispersion is a general issue when count data vary more than a statistical model expects. If it is ignored, uncertainty estimates may be too optimistic. The primary endpoint is defined as participants with an event, rather than a rate of repeated events, and the record does not specify a count model or report repeated-event results. Thus, over-dispersion cannot be assessed as a feature of the posted primary analysis. More broadly, choosing an analysis method requires matching the model to the outcome definition and the data structure; those details are not reported in the registry record.

In short, the endpoint definition supports a conceptual description of a binary linkage measure, but not a numerical estimate or a judgment about its precision. The registry record does not give the result, an analysis population, or enough methodological detail to reconstruct an inferential analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Observational Group")
n      <- c(40)
events <- c(38)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Observational Group  40  38  95.0  83.1  99.4  83.5  98.6  83.5  98.5

11. Multiplicity, Missing Data and Analysis Populations

The study summary describes several outcome areas: linkage to the pharmacy program, hepatitis C treatment initiation, completion and cure, receipt of other medications, and self-reported substance use and HIV risk behaviors. Initiation of hepatitis C treatment is specifically listed as a secondary outcome. The record lists 9 outcome measures, but it does not provide a complete account of their definitions, analysis hierarchy, or results in the information recorded. It lists 0 analyses.

When a study examines multiple outcomes, the chance of observing an apparently notable result can increase if many statistical tests are conducted. As a general statistical principle, researchers may prespecify a primary outcome, define a testing sequence, or adjust for multiple comparisons. The registry record does not report whether any such strategy was planned or used. No multiplicity adjustment or testing hierarchy can be inferred from the listed outcome count alone.

Missing-data methods and analysis populations are also not reported in the registry record. It is not stated how participants without a recorded initial evaluation, incomplete follow-up, or unavailable self-reports were handled. The record does not specify whether the primary percentage was intended to use all enrolled participants or another denominator. These details matter because excluding participants with missing outcome information can change the population represented by an estimate. Without the definitions and results, the extent or direction of any missing-data effect cannot be assessed.

These omissions do not establish that a particular analysis was or was not conducted outside the registry. They mean that multiplicity control, missing-data handling, and the population underlying any estimate are not documented in the registry record.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: hospitalization (2.5%), death (2.5%).

The safety information is listed for an observational group with 40 participants at risk. The registry records 2 serious adverse events and lists hospitalization and death among the top serious-event terms, each with a reported value of 2.5%. It separately records 1 death. The other-adverse-event field records 0 events among 40 at risk.

These are descriptive safety counts in the registry record. They do not establish whether an event was caused by the pharmacy program, related to a medication, or judged by investigators to be treatment-related; those assessments are not reported. The record does not provide event narratives, timing, severity details beyond the serious-event classification, or a comparison group suitable for estimating excess risk. The hospitalization and death terms should not be added together or treated as necessarily representing separate participants, because overlap is not described. The death count and the serious-event term are distinct pieces of registry information and should be read as recorded, not reconciled by assumption.

The absence of events in the separate other-adverse-event field does not mean that no health events of any kind occurred. The registry’s definition and reporting procedures for that field are not stated. These figures describe what was entered in the safety fields; they do not provide a comparative safety estimate.

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

The record identifies a practical question: can people who inject drugs and have hepatitis C be linked from community settings to an initial evaluation in a community-pharmacy program? It specifies that linkage is the primary endpoint and sets its timeframe at 6 months. This makes the intended outcome understandable as an early step in service delivery.

What the result means cannot be quantified from the registry record because the linkage count and percentage are not reported. Enrollment of 40 describes the listed study enrollment, not how many participants linked to the program. No confidence interval or other precision estimate is posted. The record therefore does not show the observed level of uptake or how uncertain an estimate might be.

The study summary’s broader aims include hepatitis C treatment initiation, completion, and cure, along with other services and self-reported behaviors. These are distinct from initial linkage. The record lists initiation as a secondary outcome, but does not report numerical results for it or the other stated aims. A linkage outcome, even if known, would not on its own demonstrate completion of care or a clinical outcome.

The design also limits causal interpretation. The registry describes an observational group and says this is not a randomized comparison; allocation is not stated, and the arms are not a like-for-like control comparison. A descriptive outcome could characterize participants’ experience in the program, but it would not isolate the effect of the program from other explanations.

The appropriate reading is therefore narrow: the registry defines an implementation outcome and documents a pilot study, but does not report the primary outcome result or comparative evidence. The safety entries are descriptive and do not supply a comparison of risk. Neither the study aim nor its endpoint definition should be treated as a result.

14. Why This Trial Matters Statistically

Implementation questions are statistically different from questions about whether one clinical treatment outperforms another. For this pilot, the central endpoint concerns successful linkage to a community-pharmacy program and attendance at an initial evaluation. That is an operational step in a pathway of care, and defining it makes the intended measure more concrete than a broad aim such as expanding access.

The endpoint also illustrates why clear denominators matter. A count indicates the number meeting a criterion, while a percentage depends on the group used as its denominator. For readers to interpret access or uptake, they need the endpoint count, the denominator, the follow-up window, and a description of how incomplete information was handled. The record defines the timeframe but does not report the result or denominator details.

The observational design matters for a second reason. A program’s observed use can be informative about implementation, but a comparison is needed to distinguish the program’s contribution from other factors. The registry explicitly does not describe a randomized comparison and cautions that the groups are not like-for-like controls. That distinction prevents a descriptive pilot result from being overread as a causal effect.

Finally, the distinction between linkage and later clinical outcomes is important. Reaching an initial evaluation is not the same endpoint as treatment initiation, completion, or cure. The study summary recognizes multiple steps and related services, but the registry record does not report numerical findings for them. Statistically, a well-defined process outcome can identify what a study intends to measure; it cannot substitute for missing outcome results or establish effects beyond its definition.

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.

The main limitation for interpreting the registry record is that the primary endpoint result is not reported. There is no posted linkage count, percentage, or precision estimate. Although the record lists enrollment of 40, it does not state how many participants contributed to the primary outcome or what denominator was used.

The registry describes an observational group and explicitly notes that there is no randomized comparison. Allocation is not stated, and the arms are not a like-for-like control comparison. Accordingly, the design description does not support a causal contrast between the pharmacy model and an alternative. The record does not give further information about any comparison group, if applicable, or how groups were defined.

Details needed to assess the outcome are also absent: missing-data rules, analysis populations, and the statistical analysis plan are not reported in the registry record. The record lists 0 analyses. Although it lists 9 outcome measures and names treatment initiation as secondary, the definitions and results for the wider outcome set are not reported. The multiplicity strategy is likewise not reported.

The safety information is limited to recorded counts and event terms. Causal attribution, timing, and comparative safety data are not reported. Finally, the registry’s planning illustrations are not a substitute for a trial-specific sample-size justification; the record does not report such a justification. These limitations describe gaps in the recorded information and should not be taken to imply that unreported procedures or data do not exist outside the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Hepatitis C Pharmacy-based Strategy for Injectors — NCT04698629.
• Registry record last updated 2025-04-08; status last verified 2025-03.
• Results first posted 2024-06-07.
• 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

NCT04698629 is a completed University of Washington pilot study of a community-pharmacy model for people who inject drugs and have hepatitis C. The registry lists enrollment of 40, a start date of 2020-11-05, and a primary completion date of 2023-06-30. The primary outcome is successful linkage to the pharmacy program and attendance at an initial evaluation within 6 months. Hepatitis C treatment initiation is listed as a secondary outcome.

The record describes an observational group, not a randomized comparison, and states that allocation is not stated. It lists 9 outcome measures and 0 analyses. The primary linkage result, analysis population, missing-data approach, and statistical analysis plan are not reported in the registry record. Safety fields list 2 serious adverse events, a separate death count of 1, and 0 events in the other-adverse-event field. These entries are descriptive and do not provide comparative estimates.