A Randomized Trial to Evaluated the Suppressive Effect of Acyclovir on Rapidly Cleared HSV-2 Reactivation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Randomized Trial to Evaluated the Suppressive Effect of Acyclovir on Rapidly Cleared HSV-2 Reactivation (NCT00723229), a randomized phase 4 study. The primary outcome is Frequency of HSV-2 Total Shedding From the Genital Tract as Measured by PCR, Calculated Using a Per-day Shedding Rate in Participants Treated With Suppressive Acyclovir as Compared to no Medication in HIV Seronegative and HIV Seropositive Individuals..

2. Clinical Question

3. Trial Design

This was a randomized, open-label crossover study registered as NCT00723229. It was listed as Phase 4 and completed. The registry lists enrollment of 48. The study ran from 2008-08, with primary completion in 2010-07. The sponsor was the University of Washington.

The comparison involved acyclovir 400 mg twice daily and no medication. In a crossover design, participants receive more than one study condition over time, allowing comparisons that can account for stable differences between participants. The registry identifies randomized allocation and a crossover model, but does not report the treatment sequence, period lengths, washout interval, or how the order of conditions was generated.

Masking was listed as none, so the study was open label. The primary outcome timeframe was 9 weeks. The primary-outcome population was described as participants who collected at least one swab on each study arm. The registry record does not report the full schedule of swabbing or state how many measurements were expected from each participant.

The study description focused on the frequency, duration, and quantity of genital HSV-2 shedding, including short bursts of rapidly cleared shedding. The primary endpoint was the frequency of total shedding measured by PCR. Listed secondary outcomes included the median quantity of HSV detected, the number of genital HSV shedding episodes, and their duration. The registry lists four outcome measures and three analyses, but does not provide the analysis details needed to connect each measure to a specific statistical procedure.

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.

First Intervention

Reasons for not completing this period:

Second Intervention

Analysis population for the primary outcome, as defined in the registry: Participants collected at least one swab on each study arm

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 Frequency of HSV-2 Total Shedding From the Genital Tract as Measured by PCR, Calculated Using a Per-day Shedding Rate in Participants Treated With Suppressive Acyclovir as Compared to no Medication in HIV Seronegative and HIV Seropositive Individuals., measured over 9 weeks.

The primary endpoint was frequency of HSV-2 total shedding from the genital tract, measured as the percentage of swabs with HSV detected by PCR and calculated using a per-day shedding rate. Its timeframe was 9 weeks. PCR detection provides a way to identify viral shedding in collected genital swabs, while the per-day rate expresses shedding in relation to observation time. The endpoint therefore focuses on how often HSV was detected, rather than only whether a participant ever had a detected episode.

Frequency is relevant to the trial’s stated question because the study aimed to assess whether suppressive acyclovir altered brief, rapidly cleared reactivation. The listed secondary outcomes add related but distinct dimensions: quantity of HSV detected, episode count, and episode duration. Frequency, quantity, and duration should not be treated as interchangeable. A condition could differ on one dimension without the registry record establishing a corresponding difference on another.

The registry describes the outcome population as participants who collected at least one swab on each study arm. It does not report the observed percentage of positive swabs, the per-day rates, an effect estimate comparing conditions, or a confidence interval. The outcome definition is therefore available, but the magnitude and precision of the primary comparison are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized crossover design, an open-label comparison, and a PCR-based primary endpoint. It does not report the detailed statistical methods used for the primary analysis. General statistical considerations help explain what those methods would need to address, but they should not be mistaken for procedures confirmed in this trial.

Why does the crossover structure matter?

In a crossover study, participants receive study conditions over time. Measurements from the same participant are usually related: a participant’s observations under one condition may resemble that participant’s observations under another condition more than they resemble measurements from someone else. General crossover analysis accounts for this within-participant relationship. Treating each swab as wholly independent could understate or misrepresent uncertainty if the correlation is ignored.

Period and sequence can also matter. The condition received first may be associated with time-related changes, and an effect from an earlier condition could potentially carry into a later period. A washout interval can be relevant when carryover is a concern. The registry record does not report the sequence, period lengths, washout arrangements, or how period and sequence were incorporated into analysis, so the adequacy of those features cannot be evaluated from the registry information.

What does the PCR endpoint represent?

The primary endpoint is the percentage of swabs with HSV detected by PCR, calculated using a per-day shedding rate. This is a repeated-measure outcome: multiple swabs may contribute information about shedding over the observation period. General analysis of repeated binary measurements can account for both the likelihood of detection and the correlation among measurements collected from the same participant. The registry does not identify whether the analysis used a participant-level summary, a repeated-measures model, or another method.

A rate or proportion can be summarized in different ways. A participant-level measure gives each participant a contribution to the comparison, while a swab-level analysis may make the number and timing of swabs relevant to each participant’s influence. These approaches answer related but not identical statistical questions. The outcome description alone does not show which approach was used or how unequal sampling was handled.

Why can count outcomes require special care?

Episode counts and other counts are often analyzed with methods that reflect their distribution and the amount of variation in the data. In general, over-dispersion means that observed variability exceeds what a simple count model expects. Ignoring over-dispersion can make uncertainty appear too small. This is a general statistical consideration, not a claim about the distribution or model used in this study. The registry lists episode count as a secondary outcome but does not report its values, distribution, or analysis method.

Episode duration and viral quantity also have measurement characteristics that can affect analysis. Duration may be observed through repeated sampling, and quantity can have a distribution that is not well represented by a simple average. General methods may use summaries or models suited to those features. The registry record does not state how duration or quantity was summarized, whether transformations were used, or how values below detection were handled.

How should uncertainty be read?

A confidence interval is a general way to describe the precision of an estimated effect. It shows a range of values that are reasonably compatible with the data under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, but neither alone establishes clinical importance. A p-value addresses compatibility of the data with a specified null hypothesis under a statistical model; it is not the probability that the null hypothesis is true. The registry record does not report a confidence interval, p-value, or primary effect estimate, so these features of the trial’s evidence cannot be evaluated.

The record lists three analyses, but does not describe their models, covariates, estimands, or inferential procedures. There is no basis to attribute a particular adjustment or test to the investigators. The posted sample-size planning material is described as an illustration computed from the observed effect, rather than as the trial’s original design justification. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Such planning calculations are not observed power and do not substitute for reporting the outcome estimate and its uncertainty.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and three analyses. The primary outcome is identified, along with secondary outcomes for median quantity of HSV detected, the number of genital shedding episodes, and episode duration. However, the registry record does not report a multiplicity plan describing how inference across outcomes or analyses was handled. It does not state whether a single primary comparison was designated for formal testing, whether secondary comparisons were considered exploratory, or whether any adjustment to account for multiple testing was used.

Multiplicity matters because examining multiple outcomes or analyses creates more opportunities for an apparently notable finding by chance. General approaches include prespecifying a primary contrast, adjusting inference across a defined family of tests, or explicitly treating additional results as exploratory. These are general options, not methods confirmed for this trial. Without the analysis plan and reported estimates, the strength of evidence across the listed outcomes cannot be evaluated.

Missing-data handling is also not reported in the registry record. The primary-outcome population is described as participants who collected at least one swab on each study arm, but the record does not say how incomplete sampling, missed visits, unusable swabs, or withdrawals were handled. It does not report whether all randomized participants were included in the analysis or whether any alternative analysis populations were used. The availability of at least one swab on each arm defines a population description, but does not establish how missing measurements within an arm were treated.

The record does not report an intention-to-treat definition, a per-protocol definition, imputation methods, or sensitivity analyses for missing data. These omissions limit assessment of whether the analysis population and missingness assumptions could influence the comparison.

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 1% reporting threshold.

The registry lists serious adverse event figures for the no-medication and acyclovir conditions. For each condition, 38 participants were listed as at risk for serious adverse events, and zero serious adverse events were listed. The figures for other adverse events also show 38 at risk and zero affected in each condition. These are registry counts, not estimates of comparative safety.

Zero reported events in these categories means that the record lists no events for the categories during the reported safety accounting. It does not establish that no adverse events of any kind occurred, nor does it establish that the conditions have identical safety profiles. The registry record does not report event descriptions, the observation period for safety, severity breakdowns beyond the serious-event category, or a statistical comparison.

Deaths are recorded as null for both conditions. A null value is not the same as a reported zero; the death count is not reported in the registry record. The safety figures should therefore be read narrowly, as the posted counts for the specified categories, without extending them to unreported events or outcomes.

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

The record establishes that a randomized, open-label crossover study was conducted to compare genital HSV-2 shedding during suppressive acyclovir use with shedding during no medication. It identifies the primary measurement as the percentage of genital swabs with HSV detected by PCR, expressed using a per-day shedding rate. It also lists related outcomes for quantity, episode count, and episode duration.

The record does not report the primary outcome values, an estimated contrast between conditions, or uncertainty around that contrast. It therefore does not show how much shedding was observed under either condition or how precisely any difference was estimated. The stated hypothesis about short bursts of reactivation is a study rationale, not a result. No conclusion that acyclovir did or did not suppress shedding can be drawn from the registry information alone.

The absence of a reported effect estimate is not evidence that the conditions were equivalent. An equivalence conclusion would require an appropriate design and a defined margin, along with estimates precise enough to assess that margin; these are not reported in the registry record. Similarly, a lack of a reported statistical test cannot be interpreted as a nonsignificant result.

The safety counts are limited to the adverse-event categories recorded, and the death values are not reported. They should not be generalized to all possible harms. The record also does not provide the detailed analysis methods, treatment sequence, or missing-data approach needed to assess all sources of uncertainty. Overall, the registry describes the question and design but does not provide enough outcome information to quantify the observed shedding effect or its precision.

13. Why This Trial Matters Statistically

This trial asks a statistical question that is not captured by a simple comparison of whether a participant ever had detectable HSV. Its primary endpoint uses repeated swab measurements to describe the frequency of detection over time. The focus on rapidly cleared shedding makes measurement frequency and the way repeated observations are summarized especially relevant to the interpretation.

The crossover structure can offer a within-participant comparison, which may help separate condition differences from stable differences between participants. That advantage depends on the design and analysis correctly addressing period, sequence, within-participant correlation, and potential carryover. The registry record identifies the crossover design but does not report the details needed to assess those features.

The trial also distinguishes shedding frequency from quantity, episode count, and duration. That distinction matters because these outcomes describe different properties of viral shedding. A clear statistical report would identify the estimate for each prespecified contrast, its uncertainty, and how results across multiple outcomes were interpreted. Those results and methods are not reported in the registry record.

For biostatistical interpretation, this record is a useful reminder that a clearly stated endpoint and design do not by themselves establish an effect. Quantifying evidence requires outcome values, an analysis appropriate to the sampling structure, and transparent reporting of uncertainty and missing-data handling. The trial’s listed sample-size calculations are planning illustrations based on an observed effect, not observed power or the study’s design rationale. Without the primary estimate and its precision, the central statistical question remains unresolved in the registry record.

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 for interpreting this trial from the registry record is the absence of reported primary outcome values and an estimated comparison between conditions. No confidence interval or test result is reported, so the magnitude, direction, and precision of the primary effect cannot be assessed. The secondary outcome titles are listed, but their results are not reported in the registry record either.

The design is described as randomized, open label, and crossover, but important implementation details are not reported. The treatment sequence, period lengths, washout arrangements, sampling schedule, and handling of possible period or carryover effects are not specified. These details are relevant when interpreting within-participant comparisons over time.

The registry identifies a primary-outcome population requiring at least one swab on each study arm, but does not describe the analysis population in further detail. Missing swabs, incomplete follow-up, withdrawals, and unusable specimens are not addressed. The record also does not state how PCR-negative or below-detection measurements, repeated observations, or unequal sampling were handled.

The analysis methods are not reported in sufficient detail to evaluate model choice, covariate adjustment, uncertainty estimation, or the treatment of multiple outcomes. HIV-seronegative and HIV-seropositive individuals are included in the outcome description, but subgroup results are not reported. The safety record lists zero serious and other adverse events in the specified fields, while deaths are null; these entries do not provide a complete account of all possible safety outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Randomized Trial to Evaluated the Suppressive Effect of Acyclovir on Rapidly Cleared HSV-2 Reactivation — NCT00723229.
• Registry record last updated 2017-03-09; status last verified 2017-03.
• Results first posted 2017-03-09.
• 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

NCT00723229 was a completed Phase 4 randomized, open-label crossover study sponsored by the University of Washington. The registry lists enrollment of 48, a start date of 2008-08, and primary completion in 2010-07. The comparison was suppressive acyclovir 400 mg twice daily versus no medication in HSV-2-seropositive adults.

The primary endpoint measured the percentage of genital swabs with HSV detected by PCR using a per-day shedding rate over 9 weeks. The record also lists outcomes for HSV quantity, shedding episode count, and episode duration. It does not report the primary outcome result, an effect estimate, or its precision. Serious and other adverse-event fields list zero affected in each condition; death values are not reported in the registry record.