Accessible HCV Care Intervention for People Who Inject Illicit Drugs (PWID): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Accessible HCV Care Intervention for People Who Inject Illicit Drugs (PWID) (NCT03214679), a randomized na study. The primary outcome is Proportion of Patients to Achieve SVR12 at 1 Year.

2. Clinical Question

3. Trial Design

The registry describes NCT03214679, titled Accessible HCV Care Intervention for People Who Inject Illicit Drugs (PWID). It is a completed, randomized, parallel-group trial with no masking. The registry lists the phase as NA and enrollment as 167. The sponsor is City University of New York, School of Public Health. The recorded start date is 2017-07-20, and the primary completion date is 2021-06-30.

The comparison is between Accessible Care and Usual Care. Accessible Care was organized at a collaborating needle exchange program, with a hepatitis treatment provider and a Hepatitis C Care Coordinator located on site. Usual Care involved referral to existing services, with a care coordinator assisting with insurance and connection to an HCV medical provider. The registry’s descriptions emphasize that the care pathways differed in where and how care was accessed.

The primary outcome is the proportion of patients achieving SVR12 at one year. The registry defines SVR12 as HCV RNA below the limit of quantification twelve weeks after completion of HCV treatment, and says each participant would be assessed at one year after entry. Two participants described as ineligible were excluded after randomization and are not included in outcome or adverse-event analyses. The registry does not report further details about the randomization procedure, allocation concealment, or the trial’s original sample-size justification.

The study description says that feasibility, acceptability, safety, effectiveness, and cost were under study, and that substance use and HIV and HCV risk behaviors were secondary outcomes. The registry record posts no secondary outcome results. The posted primary result therefore addresses the recorded SVR12 outcome, not every aim described in the study summary.

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: 2 ineligible participants excluded post-randomization are not included in any of the outcome or AE analyses

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: 2 ineligible participants excluded post-randomization (both accessible care arm) are not included

6. Primary Endpoint

The registry lists the primary outcome as Proportion of Patients to Achieve SVR12 at 1 Year, measured over each participant will be assessed at 1 year post entry.

The primary endpoint is the count of participants who achieved SVR12, reported for each arm and assessed at one year after entry. SVR12 means that HCV RNA is below the limit of quantification twelve weeks after HCV treatment has ended. The endpoint is therefore a virologic measure after treatment rather than a measure of treatment initiation, care attendance, or referral alone.

The registry’s study description calls sustained virologic response virologic cure. In statistical terms, the endpoint converts each participant’s result into a binary outcome: the participant either met the stated SVR12 definition or did not. The arm-level counts and the numbers at risk are the posted inputs for comparing the proportions that met the endpoint.

Why use this outcome? As a general explanation, a prespecified outcome gives the trial a defined target for comparing care strategies. A virologic endpoint can distinguish completion of the intended virologic response from intermediate steps in care, such as being linked to a provider. That distinction matters because the study’s broader aims include engagement and retention, while the primary endpoint specifically concerns the virologic response after treatment.

The registry does not report the endpoint’s missing-data handling or describe how participants without an observed SVR12 result were classified. The outcome description does say that two participants deemed ineligible after randomization were excluded from outcome analyses.

7. Results Posted in the Registry

• Accessible Care: 67.1% (55/82) versus 22.9% (19/83) on control; risk difference 44.2 percentage points (95% CI 30.6 to 57.8), risk ratio 2.93 (1.92–4.47); unadjusted two-proportion z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a randomized, parallel-group comparison without masking. The primary outcome is binary: the record gives a count of participants achieving SVR12 in each arm, along with the number included in that arm’s analysis. The recalculated comparison uses these posted summary counts as an unadjusted comparison of proportions. It is not an adjusted model, and it does not incorporate participant-level covariates.

What does the unadjusted risk ratio describe?

As a general explanation, a risk ratio compares the event proportion in one group with the event proportion in a reference group. A value above one means the event proportion is larger in the group named first, relative to the reference group. The recalculated risk ratio is 2.93 for Accessible Care compared with Usual Care, with a confidence interval from 1.919 to 4.473. This is a relative scale: it does not state the absolute difference in the proportions and does not describe the outcome for any individual participant.

The comparison also includes a risk-difference estimate and interval in the underlying statistical output. A risk difference is an absolute-scale contrast between proportions. The posted bounds are 0.306 and 0.578, while the point estimate is 0.442. Those values use more than three decimal places, so they are not repeated in this explanation. The interpretation of either scale depends on the endpoint definition and the population included in the analysis.

What does the chi-squared test assess?

The sponsor reports a chi-squared test of superiority and p <.001. As a general explanation, a chi-squared test assesses whether the observed distribution of a categorical outcome across groups is compatible with a null hypothesis of no association. Here, the categorical outcome is whether a participant achieved SVR12. The test’s p-value describes how unusual data at least as discrepant as those observed would be under the null model and its assumptions; it is not the probability that the null hypothesis is true.

The unadjusted recalculation reports p < 0.001. The sponsor’s test and the recalculation both indicate strong evidence against equal outcome proportions under their respective reported test formulations. The p-values differ in their written formatting, but both are reported as less than the stated threshold. The registry does not give the test statistic, degrees of freedom, or an adjusted analysis result.

Why does the confidence interval matter?

As a general explanation, a confidence interval represents a range of estimates compatible with the observed data under a specified statistical procedure. It communicates uncertainty about an estimated contrast, rather than only whether a null-hypothesis test crossed a threshold. For the recalculated risk ratio, the reported interval does not include one, the value corresponding to equal proportions on the ratio scale. The interval nevertheless allows a range of effect sizes; it does not make the estimate exact.

These recalculations are simple and unadjusted. They use posted summary statistics, not individual records, and they cannot account for covariates, clustering, treatment adherence, or other features unless those are represented in the reported summaries. The registry record does not report such a model for the primary comparison. It also does not report the original statistical analysis plan, an interim-analysis plan, or the sample-size justification.

What is not established by the reported methods?

Randomization is intended, in general, to support a comparison by allocating participants to groups independently of their measured or unmeasured characteristics. It does not guarantee that all relevant characteristics are balanced in a particular trial, and the registry record does not post baseline characteristics for this comparison. No masking was used, so participants and study personnel were not blinded according to the registry entry. The record does not state whether outcome assessors or laboratory staff were masked.

The primary result concerns the participants included in the outcome analysis after the stated post-randomization exclusions. The registry record does not describe other missing results, imputation, sensitivity analyses, or an intention-to-treat analysis. The recalculated test should therefore be understood as a summary-statistic comparison of the posted counts, not as a substitute for a fuller analysis plan or participant-level reanalysis.

10. Confidence Intervals and Precision

The recalculated risk ratio is 2.93, with a confidence interval from 1.919 to 4.473. The interval lies above the ratio value corresponding to equal proportions, so it is consistent with a higher observed SVR12 proportion in Accessible Care than in Usual Care. Its width also shows that the data are compatible with a range of relative effect sizes; the point estimate alone should not be treated as exact.

The recalculated risk-difference interval is reported as 0.306 to 0.578, with an estimate of 0.442. These values give an absolute-scale expression of the comparison, but are not reproduced with altered rounding. The interval excludes zero, the value corresponding to no absolute difference. The registry record does not state the confidence level attached to the recalculated intervals, so no confidence level is assigned in this explanation.

As a general explanation, interval precision depends on the amount and pattern of information in the data and on the statistical method. An interval is not a guarantee that the true effect lies within its limits, and its endpoints are not a range of individual participant outcomes. The observed counts are 55 of 82 in Accessible Care and 19 of 83 in Usual Care; these counts describe the analyzed groups, while the intervals describe uncertainty in estimated group contrasts.

The confidence intervals do not address all sources of uncertainty. They do not resolve the implications of excluding two participants after randomization, account for any unreported missing outcome data, or establish that the result applies beyond the trial setting. The registry record does not report subgroup intervals or adjusted estimates. Precision should therefore be read as uncertainty around the unadjusted contrast calculated from the posted summary counts, rather than as a complete assessment of uncertainty about every possible interpretation.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning display gives participants per arm for the stated power levels. Its rows illustrate planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For example, planning for 75% of the observed effect corresponds to 33 participants per arm for 80% power and 44 participants per arm for 90% power. Planning for 50% of the observed effect corresponds to 71 participants per arm for 80% power and 95 participants per arm for 90% power.

The calculation assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect. These are planning illustrations based on the observed effect, not the trial’s original design assumptions. The registry record does not report the original sample-size justification or the assumptions used to plan enrollment.

The 80% power column indicates the participants per arm estimated to give an 80% chance of detecting the stated effect under the planning assumptions, if that effect and those assumptions were true. The 90% power column expresses the corresponding planning target for a 90% chance. Higher target power requires more information under otherwise unchanged assumptions. The listed figures are participants per arm, not total sample sizes or total events.

Smaller effects require more participants to detect under these assumptions: the planning figures rise as the assumed effect moves from 100% to 75% and then 50% of the observed effect. The curve should be read as the same planning relationship across effect sizes, not as a depiction of outcomes observed during the trial. These figures are not observed power.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.229; treatment proportion p₁ = 0.671; average p̄ = 0.450.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7035 = 1.3789.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6304 = 0.5305.
4. n = (1.3789 + 0.5305)² / (0.4418)² = 18.7, rounded up to 19 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.228915662650602                          # control proportion
p1 <- 0.670731707317073                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3214679)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 19 (80% power), 25 (90% power)
 75% of observed effect: n per arm = 33 (80% power), 44 (90% power)
 50% of observed effect: n per arm = 71 (80% power), 95 (90% power)
power.prop.test: 18.7 
Simulated power at n = 19 per arm: 0.816 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Analyses Reported by the Sponsor

The sponsor’s own reported comparison is a chi-squared test of superiority for Accessible Care versus Usual Care, with p <.001. The unadjusted recalculation from the posted arm counts reports p < 0.001, along with the recalculated risk ratio and confidence interval. Both analyses point in the same direction and report a p-value below the stated threshold. The discrepancy flag is false, so the record does not identify a conflict between the sponsor’s analysis and the recalculation.

The sponsor’s reported result is the trial’s own analysis and takes precedence over a simple recalculation from summary statistics. The recalculation is useful as a transparent, unadjusted comparison of the posted counts, but it does not reproduce an analysis plan or account for methods not described in the registry. The sponsor’s entry does not include a test statistic, a confidence interval, or a detailed model specification. The registry record does not report whether the sponsor’s test was adjusted for covariates or otherwise modified.

The two p-value formats should not be mistaken for evidence of a substantive disagreement: both state that the p-value is below the respective displayed threshold. The registry record does not provide enough analysis detail to determine whether the sponsor’s calculation used a continuity correction or other test-specific choices. The principal interpretation should therefore retain the sponsor’s own chi-squared superiority finding while treating the recalculation as a supplementary unadjusted check.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and one reported analysis. The study summary describes SVR12 as the primary outcome and identifies substance use and HIV and HCV risk behaviors as secondary outcomes. However, the registry record posts no secondary outcome results. It also does not report a multiplicity-adjustment procedure or explain how testing across outcomes was handled.

As a general explanation, multiplicity arises when multiple hypotheses or outcomes are examined. Repeated testing can increase the chance of finding at least one result that appears statistically notable even when there is no effect. Whether adjustment is appropriate depends on the prespecified analysis plan and the intended interpretation of the outcomes. Since that plan and an adjustment strategy are not reported in the registry record, the degree to which multiplicity was addressed cannot be assessed.

The primary outcome description states that two participants deemed ineligible after randomization were excluded from all outcome and adverse-event analyses. The registry record does not report whether other primary outcome values were missing, how missing outcomes were handled, or whether sensitivity analyses were performed. It does not describe an imputation method or provide a complete participant-flow account for the endpoint.

As a general explanation, an analysis population defines which participants contribute to a result. An intention-to-treat analysis usually seeks to retain participants in their randomized groups, while other analysis populations may apply eligibility or outcome-availability rules. The record does not identify the primary analysis population using such a label. Its explicit statement about the two post-randomization exclusions is therefore important, but does not establish how all other participants or unavailable measurements were treated.

The registry also does not report interim analyses, stopping rules, a prespecified statistical analysis plan, or the sample-size justification. These omissions do not prove that such procedures were absent; they mean the relevant details are not reported in the registry record. Interpretation of the posted p-value and effect estimates should be limited to the information the record documents.

15. 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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: mental health hospitalization (4.9%), hospitalizations related to overdose (3.7%), skin/soft tissue infection (2.4%), asthma/shortness of breath (2.4%), pneumonia (1.2%).

The adverse-event record lists serious adverse events among 12 of 82 participants at risk in Accessible Care and 11 of 83 participants at risk in Usual Care. It records zero other adverse events in each arm. Deaths are listed as 3 in Accessible Care and 1 in Usual Care. These are the registry’s posted counts; they are not adjusted comparisons, and the record does not provide a statistical test or confidence interval for these safety outcomes.

The reported serious-event terms include mental health hospitalization at 4.9%, hospitalizations related to overdose at 3.7%, skin or soft tissue infection at 2.4%, asthma or shortness of breath at 2.4%, pneumonia at 1.2%, and alcohol withdrawal seizure at 1.2%. The registry does not specify in this entry whether these categories are mutually exclusive, so the percentages should not be added or treated as a partition of all serious events.

As a general explanation, an at-risk denominator indicates the group to which the adverse-event count is attached. Counts alone do not show whether event timing, duration, recurrence, or severity differed between groups beyond the recorded serious-event classification. The registry record does not provide event narratives or an adjusted safety analysis. These data describe recorded events during the study and should be interpreted separately from the primary SVR12 comparison.

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

The posted primary outcome shows more participants achieving SVR12 in the Accessible Care arm than in the Usual Care arm: 55 of 82 compared with 19 of 83. The sponsor’s chi-squared superiority analysis reports p <.001, and the unadjusted recalculation reports p < 0.001. The recalculated risk ratio is 2.93, with a confidence interval from 1.919 to 4.473. Together, these statistics describe a marked difference in the observed primary outcome between the analyzed groups.

This is a result about the endpoint as defined in the registry: HCV RNA below the limit of quantification twelve weeks after treatment completion, with assessment at one year after entry. It does not directly quantify other outcomes named in the study description, including linkage, engagement, retention, substance use, HIV and HCV risk behaviors, feasibility, acceptability, or cost. No secondary outcome results are posted in the registry record.

The comparison does not by itself show how the care strategies would perform in every population or service setting. The registry record describes a particular Accessible Care model situated at a collaborating needle exchange program and a usual-care pathway based on referral to existing services. It does not report detailed implementation measures or enough information to assess how closely these models might match other services.

The outcome analysis excludes two participants who were deemed ineligible after randomization. The registry record does not describe other missing data or the treatment of missing outcomes. The posted result therefore should not be interpreted as a complete account of all randomized participants without qualification. Nor does a low p-value establish the size, durability, or practical implications of a result beyond the stated endpoint and follow-up description.

These statistics describe the trial record; they are not medical advice or a recommendation about individual care. They support a comparison of the reported outcomes under the trial’s recorded analysis, while leaving questions about secondary outcomes, missing data, broader applicability, and the original analysis plan unresolved.

17. Why This Trial Matters Statistically

This trial is statistically informative because it compares a care-delivery approach with usual referral pathways using random allocation and a clearly stated primary endpoint. The endpoint is not merely contact with a provider: it is SVR12, defined by a virologic threshold after treatment. That allows the central comparison to focus on a measurable health outcome while the study description also recognizes that access, engagement, and retention are important parts of the care pathway.

The size of the posted difference makes it useful to examine both relative and absolute scales rather than relying on a p-value alone. The recalculated risk ratio is 2.93, and its confidence interval extends from 1.919 to 4.473. The arm-level counts, 55 of 82 and 19 of 83, provide context for that relative estimate. The sponsor’s reported chi-squared result and the unadjusted recalculation are concordant in indicating a difference in observed outcome proportions.

At the same time, the record illustrates why statistical significance is not the whole analysis. Two participants were excluded after randomization, the handling of other missing results is not reported, secondary outcome results are absent, and the registry does not provide the original sample-size rationale or full analysis plan. Those gaps matter when readers assess how robustly the result answers the broader study aims.

For biostatisticians and clinical researchers, the study highlights the value of keeping outcome definition, analysis population, effect scale, precision, and reporting completeness in view together. The result can be described clearly without overstating what the registry record establishes.

18. 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 registry record does not report several details needed for a full assessment of the trial’s conduct and analysis. It does not give the randomization method, allocation concealment procedures, baseline characteristics, or whether any outcome assessors were masked. It records no masking overall. These omissions limit evaluation of potential differences between groups and of how outcome assessment was conducted.

Two participants deemed ineligible were excluded after randomization from outcome and adverse-event analyses. The record does not explain the eligibility decision or report whether other participants lacked an observed primary outcome. It does not describe an intention-to-treat analysis, imputation, sensitivity analyses, or how missing outcomes were classified. These issues make the analysis population and possible influence of exclusions difficult to assess fully.

The registry posts no secondary outcome results, despite the study summary naming substance use and HIV and HCV risk behaviors as secondary outcomes. The record also does not post results for feasibility, acceptability, or cost, which are part of the stated study aims. It provides only limited safety detail and no statistical comparison for adverse events.

The sponsor’s analysis is reported as a chi-squared superiority test, but the record does not give a test statistic, detailed model specification, or confidence interval for that analysis. The registry does not report a statistical analysis plan, multiplicity strategy, interim-analysis plan, stopping rules, or the original sample-size justification. Planning figures based on the observed effect cannot fill those gaps.

Finally, the registry descriptions do not establish how representative the trial participants or service settings were of other contexts. The record describes care through a needle exchange program and referral to existing services, but does not provide enough implementation detail to assess variation in delivery. These are limits of what is reported, not proof that unreported procedures or analyses were not conducted.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Accessible HCV Care Intervention for People Who Inject Illicit Drugs (PWID) — NCT03214679.
• Registry record last updated 2023-02-22; status last verified 2021-07.
• Results first posted 2023-02-22.
• 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.

22. Record Summary

NCT03214679 is a completed, randomized, parallel-group trial with no masking, comparing Accessible Care with Usual Care for people who inject drugs in hepatitis C care. The registry lists enrollment as 167 and identifies SVR12 at one year as the primary outcome. SVR12 is defined as HCV RNA below the limit of quantification twelve weeks after HCV treatment completion.

The posted primary counts are 55 of 82 participants for Accessible Care and 19 of 83 for Usual Care. The sponsor reports a chi-squared superiority test with p <.001. The unadjusted recalculation reports a risk ratio of 2.93, with a confidence interval from 1.919 to 4.473, and p < 0.001. Two participants deemed ineligible after randomization were excluded from outcome and adverse-event analyses.

The registry record posts serious adverse-event counts and deaths, but no secondary outcome results. It does not report the original sample-size justification, a detailed statistical analysis plan, or the handling of other missing outcome data.