Conversion to Envarsus Post Kidney Transplant Protects Against BK Infection: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Conversion to Envarsus Post Kidney Transplant Protects Against BK Infection (NCT03762473), a non-randomized phase 2 study. The primary outcome is Participants Will Experience Less BK Infection Episodes Based on Viruria Results..

2. Clinical Question

The study asks whether changing from immediate-release tacrolimus to Envarsus in rapid metabolizers after kidney transplantation is associated with fewer episodes of BK infection. Its stated primary measure is BK viruria, defined in the registry record as urine BK virus greater than 500 copies, from baseline to 30 days. The record also describes evaluation of serum and urine BK measurements and review of biopsies for BK virus nephropathy, along with rejection, graft failure, and graft dysfunction.

The intended clinical question is therefore distinct from what can be concluded from the posted record. The record documents the study’s aim and design, but it does not provide a primary endpoint estimate or a statistical comparison of the groups.

3. Trial Design

The registry lists this as a phase 2, parallel, non-randomized study with no masking. The recorded enrollment is 89. The two groups are called Study Group and Control Group. The study group is described as post-transplant patients who would convert to Envarsus; the control group is described as post-transplant patients treated with standard-of-care immunosuppression. The control description refers to patients transplanted between 10-2016 and the time of enrollment, making this a historical rather than randomized comparison.

Eligibility descriptions mention kidney transplantation alone, standard-of-care immunosuppression, BK screening, and concentration-to-dose status. The study-group description also mentions no prior rejection, prior BK, or opportunistic infection. The text for both arm descriptions ends mid-sentence. Consequently, the full inclusion and exclusion rules, the precise definition of rapid metabolizer, and any group-selection details are not reported in the registry record.

The study began on 2019-05-09, had a primary completion date of 2022-03-16, and is listed as completed. The record identifies the University of Alabama at Birmingham as sponsor. Although it lists 20 outcome measures, it records no outcome analyses. The primary endpoint population is explicitly described as data not gathered for the stated period.

Because assignment was non-randomized, differences between groups could reflect factors beyond the intervention, including how participants were selected or when they entered care. The registry record does not report an adjustment strategy that would address such differences. Its posted safety group counts also do not account for every participant in the recorded enrollment, and the reason for that difference is 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: data not gathered for this time 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.

6. Primary Endpoint

The registry lists the primary outcome as Participants Will Experience Less BK Infection Episodes Based on Viruria Results., measured over From baseline to 30 days.

The primary endpoint is described as the number of participants experiencing fewer BK infection episodes based on viruria results, with evidence of BK virus infection defined as viruria greater than 500 copies. The measurement window is stated as from baseline to 30 days. In general, a urine viral measurement can serve as a marker of viral presence in the urinary tract; the registry’s threshold specifies how this study intended to classify evidence of infection. It does not, by itself, describe the severity of illness or establish that a clinical complication occurred.

The endpoint is relevant to the stated study question because the trial aimed to assess BK infection after conversion to Envarsus. The record also mentions urine and serum BK values at specified time points and biopsy review for BK virus nephropathy, but those descriptions do not replace the stated primary endpoint definition. The outcome population for the primary endpoint is recorded as data not gathered for this time period. No event count, group estimate, uncertainty interval, or test result for this endpoint is reported in the registry record.

The phrase “participants will experience less” expresses the intended direction of the question, not an observed result. Without endpoint data, the registry record cannot establish whether the groups differed in viruria during the stated period.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does non-randomized allocation mean for interpretation?

In general, random allocation is intended to make treatment groups comparable with respect to both measured and unmeasured characteristics. This study is listed as non-randomized, so that protection is not part of its design. The study group received the conversion intervention, while the control group consisted of patients who received standard-of-care immunosuppression and were identified from an earlier transplant period. Differences in patient characteristics, care practices, follow-up, or selection into a group could therefore be associated with the outcome as well as the intervention. These are potential sources of confounding, not evidence that any particular bias occurred.

A credible non-randomized comparison generally needs clear information about eligibility, group formation, timing, outcome ascertainment, and any statistical adjustment. The registry arm descriptions are truncated, and the statistical analysis plan and adjustment methods are not reported in the registry record. It is consequently not possible to determine from this record whether or how comparability was assessed.

What can an endpoint estimate tell readers?

In general, an endpoint estimate summarizes an outcome in a defined population and time window. For a group comparison, an estimate would express the observed contrast using a stated measure, such as a difference in event frequency or a time-to-event measure. Its meaning depends on how the endpoint was defined, who was included, and how missing observations were handled. Here, the registry defines evidence of BK infection as urine viruria greater than 500 copies and states a period from baseline to 30 days. It also says data were not gathered for that time period, so an endpoint estimate is not reported in the registry record.

A confidence interval, in general, describes the range of values compatible with an estimate under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, but neither an interval nor a point estimate can remove bias from a non-randomized design. No confidence interval for the primary endpoint is reported in the registry record.

Why does the analysis population matter?

In general, an analysis population defines which participants contribute data to a particular outcome. Different rules can produce different estimates, especially when participants do not have outcome measurements or when eligibility changes after enrollment. A report should describe the population, exclusions, follow-up, and handling of missing observations. The registry record does not report a primary endpoint population with collected data; instead, it states that data were not gathered for the primary measurement period. The analysis population and missing-data procedures for other outcomes are not reported in the registry record.

How should sample-size planning be read?

The planning illustrations use an observed effect as the target for hypothetical calculations and state assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation. The assumptions also specify that the target effect is a stated fraction of the observed effect. In general, a sample-size calculation estimates how many participants or events a future or planned study would require under chosen assumptions. Such a calculation is sensitive to the assumed effect, outcome variability, allocation, significance threshold, and statistical model. It does not establish that a study was adequately designed, and it is not a measure of the probability that the observed result is true.

The record says that time-to-event calculations use a total event count, while other calculations use participants per arm. These planning conventions do not describe the actual enrollment or observed endpoint results. The numerical illustrations and the observed effect used to generate them are not reported in the registry record posted for this analysis; their assumptions cannot be independently assessed from the recorded endpoint information.

What does over-dispersion mean in general?

For count outcomes, a statistical model may assume a particular relationship between the average outcome and its variability. Over-dispersion means the observed variability exceeds what a simpler count model assumes. If it is ignored, standard errors can be too small and uncertainty can appear overstated as precision. Analysts may use a model that allows additional variation or use robust uncertainty estimates, depending on the data and design. This is general statistical context only: the registry record does not report whether the primary endpoint was analyzed with a count model, whether over-dispersion was assessed, or what method was used for uncertainty estimation.

More broadly, the record does not report the statistical model, test, covariates, assumptions checks, interim analyses, or prespecified analysis plan. Those details should not be inferred from the phase designation, endpoint description, or planning assumptions. With no posted primary outcome analysis, there is no basis for evaluating model fit, estimating an adjusted effect, or judging the precision of the intended comparison.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 20 outcome measures, including repeated descriptions of an evaluation of estimated glomerular filtration rate and proteinuria. It does not report a multiplicity strategy, such as prioritization of outcomes, adjustment of significance thresholds, or a hierarchical testing plan. In general, testing many outcomes can increase the chance of at least one apparently notable result arising by chance. Adjustment or prespecification can help readers understand how multiple findings were intended to be interpreted. The record does not establish which outcomes were treated as confirmatory or how multiplicity was handled.

Missing-data information is also limited. For the primary endpoint, the population is described as data not gathered for the stated time period. The registry record does not explain why the data were not gathered, whether measurements were unavailable for all participants, or whether the endpoint period changed. It does not report imputation, censoring, sensitivity analyses, or other approaches to missing observations. Those details are not reported in the registry record.

The record does not describe analysis populations for the secondary outcomes, participant flow, or exclusions from analyses. The difference between recorded enrollment of 89 and the safety group denominators is not explained. Without outcome-specific denominators and missingness information, readers cannot assess whether the posted safety summaries cover the same population as the efficacy outcomes or whether missing observations could affect interpretation.

In general, multiplicity and missingness are distinct issues: multiplicity concerns interpretation across outcomes or tests, while missingness concerns absent measurements and the assumptions used to handle them. Both can affect how confidently results are interpreted. Here, the lack of posted primary outcome analyses and the absence of reporting on these procedures leave those questions unresolved.

11. 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 summaries list 43 participants at risk in the Study Group and 45 in the Control Group. Serious adverse events affected 0 participants in each group; other adverse events also affected 0 participants in each group. The record lists one death in the Study Group and no deaths in the Control Group. No serious adverse event terms are listed.

These figures are descriptive counts, not evidence from a randomized safety comparison. The groups were not randomly assigned, and the registry record does not report statistical comparisons, follow-up duration for these safety figures, event definitions, or the relationship of the death to treatment. A count of zero affected participants means no events are recorded in that category for the posted group summary; it does not establish that no event occurred outside the reported collection or reporting process.

Deaths are listed separately from serious adverse event counts in the record, so the death count should not be folded into the serious adverse event figures. The registry record does not describe the cause of death. It also does not explain why the safety denominators differ from the recorded enrollment of 89. These counts should therefore be read as the safety information posted in the registry, not as a complete account of comparative risk.

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

The registry record establishes that a phase 2, non-randomized study was intended to examine BK viruria after conversion from immediate-release tacrolimus to Envarsus in rapid metabolizers after kidney transplantation. It defines the primary measure as viruria greater than 500 copies over a period from baseline to 30 days. It also describes secondary assessments concerning graft function, proteinuria, rejection, graft failure, and graft dysfunction.

It does not establish whether conversion was associated with fewer BK infection episodes. The primary endpoint population is recorded as data not gathered for the stated period, and no outcome analyses are listed. There is no posted primary endpoint estimate, group contrast, confidence interval, or statistical test result. Accordingly, the study’s intended direction should not be confused with an observed finding.

The design also limits causal interpretation. Non-randomized treatment assignment and a control group drawn from an earlier period can leave groups different in ways that affect outcomes. The registry record does not report whether adjustment was performed or provide enough analysis detail to evaluate confounding. Even if a numerical association were available, it would not automatically establish that the intervention caused it.

The safety counts report no participants affected by serious or other adverse events in either group, and report one death in the study group and none in the control group. These limited summaries do not explain event ascertainment, follow-up, or cause, and do not provide a comparative safety analysis. They should not be generalized beyond the posted counts.

The appropriate conclusion is therefore about the record, not treatment efficacy: it documents the study question, design, endpoint definition, and limited safety summaries, but does not provide the primary outcome data needed to answer the stated question. This is not evidence of no difference; it is an absence of a reported primary comparison.

13. Why This Trial Matters Statistically

This study is statistically important as an example of why a clearly stated research question and a defined endpoint are not enough to support an effectiveness conclusion. The registry describes an intervention, a comparator, and a BK viruria threshold, but reports that data for the primary measurement period were not gathered. Without an outcome estimate and its uncertainty, readers cannot assess either the direction or the precision of the intended comparison.

The non-randomized design also makes the comparison’s structure important. The control group is described as historical, while the intervention group underwent conversion after transplant. Statistical adjustment can sometimes address observed differences between groups, but it cannot automatically eliminate unmeasured confounding. The registry record does not report whether an adjustment strategy was used, so the extent to which potential group differences were addressed is unknown.

The record further illustrates the distinction between enrollment and analysis. Enrollment is recorded as 89, while the safety summaries list 43 and 45 participants at risk. Without participant flow or outcome-specific denominators, readers cannot determine how the recorded enrollment relates to the available safety data or to the unreported primary endpoint.

Finally, planning calculations and safety counts answer different questions from the primary outcome analysis. Sample-size planning illustrations describe hypothetical requirements under stated assumptions; they are not observed effects or observed power. Safety counts describe recorded events but do not establish a treatment effect. Keeping these pieces separate prevents design information from being mistaken for evidence about the primary clinical question.

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.

Important trial-specific limitations include the absence of reported primary endpoint data for the stated baseline-to-30-day period and the lack of posted outcome analyses. The endpoint population is explicitly described as data not gathered for that period, but the reason is not reported in the registry record. Without endpoint observations, no estimate of the intended group difference or its precision can be assessed.

The comparison is non-randomized, and the control group is described as drawing on patients transplanted during an earlier period. That structure permits potential differences in patient selection, clinical characteristics, and care over time to influence a comparison. The registry record does not report adjusted analyses or details needed to evaluate those possibilities.

The arm descriptions are truncated, leaving the full eligibility criteria and group-selection process unclear. The record does not report a statistical analysis plan, analysis populations, missing-data procedures, multiplicity handling, or details of outcome ascertainment beyond the endpoint description. It also does not explain the difference between recorded enrollment and the safety denominators.

Safety reporting is limited to group counts, with no serious adverse event terms listed. The record does not report event details, follow-up duration for these counts, or the cause of the recorded death. These limitations mean that neither the primary efficacy question nor a comprehensive comparative safety question can be resolved from the posted registry information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Conversion to Envarsus Post Kidney Transplant Protects Against BK Infection — NCT03762473.
• Registry record last updated 2023-07-27; status last verified 2023-07.
• Results first posted 2023-07-27.
• 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

NCT03762473 is listed as a completed phase 2, parallel, non-randomized study sponsored by the University of Alabama at Birmingham. It began on 2019-05-09, reached primary completion on 2022-03-16, and has recorded enrollment of 89. The study intended to assess conversion from immediate-release tacrolimus to Envarsus in rapid metabolizers after kidney transplantation, with a non-randomized control group.

The primary endpoint concerns BK viruria greater than 500 copies from baseline to 30 days. The registry record states that data were not gathered for that period and lists no outcome analyses. Safety summaries report no participants affected by serious or other adverse events in either group, one death in the study group, and none in the control group. The posted record describes the research aim and design but does not report the primary results needed to answer its main question.