Pre-engraftment Cytomegalovirus DNAemia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pre-engraftment Cytomegalovirus DNAemia (NCT03889028), a registered phase not stated study. The primary outcome is Time to Engraftment (Days) Stratified by CMV DNaemia Occurring Before or After Neutrophil's Engraftment.

2. Clinical Question

The clinical question concerns the timing of cytomegalovirus (CMV) DNAemia in allogeneic hematopoietic stem cell transplant recipients and its relationship to neutrophil engraftment and clinical outcomes. The primary endpoint is time to engraftment, compared across patients with CMV DNAemia occurring before or after neutrophil engraftment. The registry also lists overall mortality and non-relapse mortality as secondary outcomes. A separate group is described as having no CMV DNAemia in the adverse-event information.

This is a question about the timing and observed outcomes of CMV DNAemia, not a randomized comparison of assigned treatments. The registry record does not state an allocation method, and it does not identify a randomized treatment intervention or a like-for-like control comparison. The reported groups therefore should not be read as treatment arms created by random assignment.

3. Trial Design

The registry identifies this study as “Pre-engraftment Cytomegalovirus DNAemia” and describes its focus as incidence, risk factors and clinical outcomes among allogeneic hematopoietic stem cell transplant recipients. The listed enrollment is 878. The record gives a study start date of 2019-09-02, a primary completion date of 2020-09-01, and a status of completed. The sponsor is Fundación para la Investigación del Hospital Clínico de Valencia.

The comparison of interest is stratification by whether CMV DNAemia occurred before or after neutrophil engraftment. The record also lists patients with no CMV DNAemia in the adverse-event information. These categories are not described as randomized arms: the registry’s comparison note says allocation was not stated and cautions that the groups are not a like-for-like control comparison. The record does not establish how participants entered each category or whether the categories were defined in advance.

The primary outcome is time to engraftment, with a 30-day timeframe. Its description defines engraftment using an absolute neutrophil count ≥500/mm3 on 3 consecutive days, with the first of those days being the time of engraftment. The primary outcome is described for patients with CMV DNAemia and stratified by whether DNAemia occurred before or after engraftment. Overall mortality and non-relapse mortality are listed as secondary outcomes.

The registry record does not report a detailed protocol, a randomization method, masking, a control-treatment assignment, or the statistical analysis plan. It also does not report results for the primary endpoint or sponsor-reported hazard ratios. Those omissions limit what can be concluded about how the study was conducted and how precisely the outcomes were estimated.

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

Analysis population for the primary outcome, as defined in the registry: Patients with CMV DNAemia

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 Time to Engraftment (Days) Stratified by CMV DNaemia Occurring Before or After Neutrophil's Engraftment, measured over 30 days.

The primary endpoint is time to neutrophil engraftment, expressed in days. The registry describes the summary as the median with the full range, for patients with CMV DNAemia, stratified by whether CMV DNAemia occurred before or after neutrophil engraftment. The endpoint timeframe is 30 days.

Engraftment is defined as an absolute neutrophil count ≥500/mm3 on 3 consecutive days; the first day meeting that sequence marks the time of engraftment. This operational definition makes the outcome more reproducible by specifying both a count threshold and the persistence needed to meet the endpoint. Time-to-engraftment is useful because it describes when a clinical milestone occurs rather than only whether it occurs.

The median identifies the central point of the observed time distribution, while the full range describes its lowest and highest observed values. These summaries do not by themselves quantify uncertainty or account for censoring. The median, range and any inferential estimates for this endpoint are not reported in the registry record. Consequently, the record does not establish the direction, size or precision of a difference between the timing groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary summary represent?

The registry specifies a median and full range for time to engraftment. In general, the median is a measure of the middle of a distribution: observations are ordered, and the median marks its center. The full range describes the smallest and largest observed values. These summaries are descriptive. They do not, on their own, establish that two groups differ beyond what might occur from sampling variability, and a range is not a confidence interval.

The endpoint is time-based, so the observation period and treatment of participants whose engraftment time is not observed can affect the analysis. General time-to-event methods can account for incomplete follow-up through censoring, but the registry record does not report whether censoring occurred or how it was handled. It also does not report the median values, ranges or a statistical comparison for the primary endpoint.

What is a hazard ratio?

In general, a hazard ratio compares the instantaneous event rates between groups over follow-up, conditional on the model and its assumptions. It is not the same as a ratio of median times, nor does it directly provide the probability that an individual experiences an event. Its interpretation depends on which event is modeled, how groups are coded, the follow-up window and whether assumptions such as proportional hazards are reasonable.

The registry’s method note says that only sponsor-reported hazard ratios are used for time-to-event outcomes. However, no sponsor-reported hazard ratio is included in the registry record. There is therefore no hazard-ratio estimate or confidence interval to interpret. A hazard ratio should not be reconstructed from the group counts or death counts, because those summaries do not contain the follow-up and event-time information needed for such an estimate.

Why does group formation matter?

General statistical interpretation depends on how participants entered the groups. Random assignment can make treatment groups comparable in expectation, whereas groups defined by when a clinical event occurred can differ in baseline characteristics, care, follow-up or other prognostic factors. The registry note explicitly says this is not a randomized comparison and that allocation was not stated. Thus, any group differences, if reported, would be associations in the recorded groups rather than effects attributable to randomized assignment.

The timing categories also require careful interpretation because the primary endpoint is engraftment and the groups are defined in relation to engraftment. The registry describes the comparison but does not provide details sufficient to assess the exact timing rules, the handling of events near the engraftment date or the analytic strategy for this relationship. Such information would matter in assessing potential selection and time-related biases. The record does not report these details, so no specific bias can be quantified.

How should planning illustrations be understood?

The registry’s planning assumptions describe illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. They define the effect to detect as a stated fraction of the observed effect. For time-to-event planning, the assumption says the displayed event count is a total; for other outcomes, the count is participants per arm. These are planning conventions, not observed study results or evidence of study power.

In general, a sample-size calculation estimates the information that might be needed to detect a chosen effect under specified assumptions. Its interpretation depends on the effect size, variability, event frequency, allocation and analysis method. A planning illustration is not “observed power,” and it cannot substitute for an estimate with a confidence interval. Numerical illustrations and the observed effect used for them are not reported in the registry record, so their implications cannot be assessed. The record also does not report the trial’s own sample-size justification.

What does over-dispersion mean in general?

For count outcomes, a statistical model may assume a particular relationship between the mean and variability. Over-dispersion means the observed variability is greater than that assumed by a simpler model. If ignored, uncertainty estimates can be too small. This is a general statistical consideration, not a finding reported for this study. The registry record does not state that count-model methods or an over-dispersion adjustment were used.

Overall, the method information defines the endpoint and identifies a time-to-event context, but it does not provide the numerical estimates, uncertainty measures or analysis details needed to reproduce or fully evaluate the primary comparison.

10. Multiplicity, Missing Data and Analysis Populations

The record names one primary outcome, time to engraftment, and two secondary outcomes: overall mortality and non-relapse mortality. When multiple outcomes or comparisons are evaluated, general statistical practice considers whether the chance of false-positive findings across those analyses is controlled or otherwise addressed. The registry record does not report a multiplicity procedure, a hierarchy for testing outcomes, or which analyses were intended to be confirmatory. The number of registered analyses is 0; this should not be taken to mean that no analysis was conducted, but it means the registry record does not provide analysis entries to inspect.

Missing-data handling is not reported in the registry record. The record does not describe the extent or pattern of missing endpoint or covariate data, the assumptions used to handle missingness, or any imputation or sensitivity analysis. For a time-to-event endpoint, the treatment of incomplete follow-up and censoring is also not reported.

The registry does not specify the analysis populations used for the primary or secondary outcomes, such as whether the analyses included all enrolled participants or a defined subset. Although the primary endpoint population is described as patients with CMV DNAemia, eligibility details and analytic exclusions are not stated. The relationship between that population and the groups used in the mortality listings is not fully described.

Without these details, readers cannot assess whether outcome selection, missing observations or analysis-population decisions could have affected the reported findings. The registry also does not report a prespecified statistical plan, so it is not possible to compare planned analyses with completed analyses.

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 serious and other adverse-event fields list 0 affected participants for each of the three groups. The corresponding numbers at risk are 144 for Pre-CMV DNAemia, 422 for Post-CMV DNAemia and 312 for No CMV DNAemia. The registry record does not provide event terms in the serious-event listing.

These entries should be read as the counts recorded in the adverse-event fields, not as proof that no adverse events occurred. The record does not explain the collection window, reporting thresholds, completeness of adverse-event ascertainment or why the affected counts are zero. The number at risk is not a measure of exposure duration, and these fields do not report a comparison adjusted for follow-up.

Deaths are shown separately: 54, 131 and 94 for the groups, respectively. They are not the same measure as the affected counts in the serious or other adverse-event fields. The registry does not report a death-analysis timeframe, comparative estimate or uncertainty interval. These group counts alone do not establish a mortality difference or a treatment effect.

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

The record documents a study focused on CMV DNAemia around neutrophil engraftment in allogeneic hematopoietic stem cell transplant recipients. It defines an engraftment threshold and identifies time to engraftment as the primary outcome. It also lists overall mortality and non-relapse mortality as secondary outcomes, and presents group counts for deaths and adverse-event fields.

Those details do not establish whether early or later CMV DNAemia is associated with faster or slower engraftment, or with different mortality. The numerical primary endpoint results and sponsor-reported hazard ratios are not reported in the registry record. No confidence intervals or other uncertainty estimates for the mortality outcomes are reported. Descriptive group counts cannot account for follow-up time, baseline differences or other factors that may distinguish groups.

The record also does not support conclusions about the effect of a preventive or therapeutic intervention. It does not identify a randomized treatment comparison, and the registry note cautions that the comparison is not randomized and is not a like-for-like control comparison. Thus, the listed groups should not be interpreted as treatment and control groups.

In general, a clinically meaningful interpretation needs both an estimate of the outcome difference and information about its precision, along with enough design and analysis detail to assess potential bias. Those elements are not reported for the primary comparison. The registry’s completed status and listed enrollment describe the study record, but do not fill the gap in reported outcome estimates. The defensible reading is therefore limited: the registry identifies the research question and selected descriptive data, while leaving the size, direction and precision of the primary and secondary outcome relationships unreported.

13. Why This Trial Matters Statistically

The study addresses a timing question that is distinct from the more familiar observation of CMV DNAemia after engraftment. Its focus on pre-engraftment episodes makes the definition and timing of both DNAemia and engraftment central to statistical interpretation. The endpoint description gives a concrete neutrophil threshold and persistence rule, helping clarify what event is intended to mark engraftment.

Statistically, the record also illustrates why group labels and outcome counts are not enough to establish a comparative effect. The timing groups are not described as randomized, and the registry explicitly warns that they are not a like-for-like control comparison. Any observed outcome contrast would need interpretation in light of how groups formed, when follow-up began and ended, and which factors were considered in analysis. The registry record does not provide these details or the outcome estimates needed to assess them.

The separation of overall mortality and non-relapse mortality as secondary outcomes also raises questions about outcome definitions, follow-up and multiplicity. These are standard considerations when multiple endpoints are examined, but the record does not report the relevant analysis choices.

Finally, the record distinguishes time-to-event analysis from other outcome planning: it refers to sponsor-reported hazard ratios for time-to-event outcomes and describes planning illustrations as based on the observed effect. No hazard ratios or numerical planning illustrations are reported in the registry record. This makes the example useful for understanding what a registry description can establish—and what it cannot—without treating descriptive counts as a complete inferential analysis.

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 main limitation for interpreting this registered study is that outcome estimates are not reported in the registry record. In particular, the median time to engraftment, its full range and a comparison estimate are absent. Sponsor-reported hazard ratios are also not reported. Without these results, the direction, magnitude and precision of the primary endpoint comparison cannot be assessed.

The record gives limited information about study conduct and analysis. It does not report the detailed protocol, allocation method, statistical plan, analysis populations, missing-data strategy or handling of incomplete follow-up. It does not explain the timing rules used to assign DNAemia groups in sufficient detail to evaluate the consequences of classification around engraftment. The registry note says the comparison is not randomized and is not a like-for-like control comparison, so the group counts cannot be interpreted as an experimental treatment contrast.

For mortality, the record lists death counts but does not provide a defined analysis timeframe, event-time summaries, adjusted estimates or uncertainty intervals. It names overall mortality and non-relapse mortality as secondary outcomes without reporting their estimates. The adverse-event fields contain zero affected counts, but the record does not describe ascertainment or reporting procedures, limiting interpretation of those entries.

These limitations concern what the registry record reports; they do not establish that analyses or procedures were absent from the study itself. They do mean that readers cannot independently evaluate the primary result, assess the precision of secondary outcomes or determine how robust the findings are to analysis choices.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pre-engraftment Cytomegalovirus DNAemia — NCT03889028.
• Registry record last updated 2020-12-11; status last verified 2020-11.
• Results first posted 2020-12-11.
• 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

The completed registry record describes a study of pre-engraftment CMV DNAemia among allogeneic hematopoietic stem cell transplant recipients, sponsored by Fundación para la Investigación del Hospital Clínico de Valencia. It lists enrollment of 878, a start date of 2019-09-02 and a primary completion date of 2020-09-01.

The primary outcome is time to engraftment in days, summarized by median and full range among patients with CMV DNAemia and stratified by timing relative to neutrophil engraftment. Engraftment is defined by an absolute neutrophil count ≥500/mm3 on 3 consecutive days, with the first day marking engraftment. Overall mortality and non-relapse mortality are listed as secondary outcomes.

The registry includes group counts for deaths and zero affected counts in the serious and other adverse-event fields, but does not report the primary endpoint estimates or sponsor-reported hazard ratios. Allocation is not stated, and the registry cautions that the comparison is not randomized and the groups are not like-for-like controls.