The Impact of Oxidative Stress on Erythrocyte Biology: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Impact of Oxidative Stress on Erythrocyte Biology (NCT04028700), a randomized phase 2 study. The primary outcome is Percentage of Red Blood Cells Surviving.

2. Clinical Question

The study question concerns the early post-transfusion recovery of red blood cells, rather than a clinical outcome such as a sickle cell crisis. Its registry summary frames the comparison as whether red blood cells from donors with G6PD enzyme deficiency have a different lifespan after transfusion to a person with sickle cell disease. The primary outcome operationalizes that question as the percentage of red blood cells surviving, measured 24 hours post-transfusion.

The record lists two randomized sequences: G6PD-deficient transfusion followed by non-G6PD-deficient transfusion, and the reverse sequence. This makes the study a crossover trial: participants are assigned to a sequence and are intended to receive both transfusion types at different times. The record does not describe participant characteristics beyond the condition, or explain which party was masked under the single-masked designation.

The posted group summaries report a mean survival percentage of 82.91 (standard deviation 5.57; n=3) for the G6PD-deficient transfusion and 91.03 (standard deviation 3.9; n=5) for the non-G6PD-deficient transfusion. These are descriptive summaries, not a reported estimate of the within-participant treatment contrast. No formal comparison, confidence interval, or analysis result is reported in the registry record. Therefore, the clinical question is not resolved by a statistical test in the posted results.

3. Trial Design

The registry identifies this as a Phase 2, randomized, single-masked, crossover study. It lists 8 participants enrolled and the status as terminated. The study start date is 2022-01-02, and the primary completion date is 2024-07-18. The reason for termination is not reported in the registry record. The record does not report why enrollment stopped, whether the planned enrollment was achieved, or whether every participant completed both transfusion periods.

In one sequence, participants were to receive a red blood cell unit identified as G6PD-deficient by local laboratory procedures, followed after 4 months by a unit identified as not G6PD-deficient. In the other sequence, the order was reversed. Random assignment to sequence is intended to reduce systematic differences in which treatment comes first. The crossover structure also makes each participant a potential comparison with themself, because both transfusion types are described in each sequence. However, the posted arm summaries do not give the paired participant-level outcomes needed to assess that within-person contrast.

General statistical context: crossover studies can be efficient when outcomes within a participant are more alike than outcomes between participants. Their interpretation depends on the outcome being measured in each period and on how period, sequence, and possible carryover effects are handled. These design and analysis details are not reported in the registry record, so it is not possible to determine how they were addressed. The four-month spacing is stated in the sequence descriptions; the record does not state whether it was intended as a washout period or how its adequacy was assessed.

The intervention descriptions classify the transfusions by G6PD enzyme activity as identified through local laboratory procedures. Further details about those procedures, product characteristics, or any other co-interventions are not reported in the registry record. The identity of the party masked under the single-masked designation is also not reported. These omissions limit what can be concluded about implementation and the risk of bias, even though randomization and the crossover structure are specified.

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.

Initial Intervention

Washout (4 Months)

Second Intervention

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 Percentage of Red Blood Cells Surviving, measured over 24 hours post-transfusion.

The primary endpoint is the percentage of red blood cells surviving, with the outcome described as post-transfusion recovery and measured 24 hours post-transfusion. It is a continuous measure: each result represents a percentage, and the registry reports group means with standard deviations. The endpoint addresses early survival of transfused red cells, which is the biological question described in the registry summary. It is not itself a measure of longer-term clinical status or disease events.

General statistical context: a continuous endpoint preserves more gradation than a simple classification of whether an event occurred. A mean describes the average observed value in a group, while a standard deviation describes the spread of individual values around that group mean. The standard deviation is not a confidence interval and does not directly express how precisely a treatment contrast has been estimated. Precision for the contrast depends on the number of observations and, for a crossover study, on the paired outcomes and their relationship within participants.

The registry lists the endpoint timeframe as 24 hours post-transfusion. The posted summaries give a mean of 82.91 with standard deviation 5.57 for the G6PD-deficient transfusion group, and a mean of 91.03 with standard deviation 3.9 for the non-G6PD-deficient group. The record does not provide the participant-level values, an estimate of the paired contrast, or a confidence interval. Consequently, the summaries describe observed group values but do not establish the precision of the difference between transfusion types.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical context: a trial design determines what comparisons the data can support, while the analysis method determines how those comparisons are estimated and how uncertainty is represented. The registry identifies random allocation, single masking, and a crossover model. It does not report the statistical analysis plan, the model used for the primary endpoint, or any adjustment for sequence or period. The discussion below explains the relevant concepts; it does not describe an analysis confirmed to have been performed in this study.

What does a mean and standard deviation describe?

The primary outcome is continuous, and the registry reports a mean and standard deviation for each transfusion type. A mean is the arithmetic average of observed values in a group. A standard deviation describes how dispersed those values are around the mean. A larger standard deviation indicates more spread among the observed values, whereas a smaller standard deviation indicates values are more clustered. Neither statistic alone describes the uncertainty in a difference between treatments. That uncertainty also depends on the amount of data and, in a crossover study, how outcomes within the same participant are related.

A standard deviation should not be read as a confidence interval, and it does not establish whether a group mean is precisely estimated. A confidence interval for a contrast would combine the estimated effect with its sampling uncertainty under a specified statistical model. It would make clear whether the data support only a broad range of possible contrasts or a narrower range. No confidence interval for the primary contrast is reported in the registry record.

Why does crossover structure matter?

In a crossover design, participants receive treatments in a sequence, rather than remaining in only one treatment group. The sequence descriptions in this record state that both transfusion types are given, with the later transfusion following after 4 months. A typical crossover analysis uses the within-participant difference between outcomes under the two conditions. Comparing each participant with themself can account for stable characteristics that differ across participants, provided the necessary paired observations are available and the design assumptions are reasonable.

That approach differs from treating each treatment group summary as though it came from unrelated participants. A comparison based only on separate group means does not use the pairing and cannot recover the within-person variability. The registry gives arm-level summaries but not paired outcome values or the within-participant correlation. It also does not report an analysis that models treatment, period, or sequence. Therefore, the descriptive means and standard deviations cannot reconstruct the crossover contrast.

Carryover is another general consideration: effects of an earlier treatment could influence a later-period measurement. Period effects can arise if outcomes change over time for reasons unrelated to treatment, and sequence effects can reflect differences associated with treatment order. Crossover studies may address such concerns through design choices and analysis, but the record does not report the rationale for the interval, assessments of carryover, or statistical handling of period and sequence. No claim about whether these effects occurred or were ruled out is warranted.

What does randomization contribute?

Randomization assigns participants to treatment sequences by chance. In general, it can reduce systematic differences between sequence groups, including differences in measured and unmeasured characteristics. It does not ensure identical groups in a small study, and it does not remove the need to analyze outcomes according to the design. The record says the study was randomized but does not describe the randomization procedure, concealment, or allocation implementation. Those details are not reported in the registry record.

Masking can reduce the influence of expectations or knowledge of assignment on aspects of trial conduct or outcome assessment. The registry labels the study single-masked, but does not identify who was masked or what procedures maintained masking. The endpoint is a percentage measurement, but that alone does not establish whether outcome assessment was blinded. The masking designation should therefore be read as a record-level label, not as enough detail to evaluate how masking operated.

How should missing inferential results be understood?

A p-value and a confidence interval answer different but related questions. A p-value is calculated relative to a specified null hypothesis and model; it does not directly measure the probability that a treatment is effective. A confidence interval describes uncertainty around an estimated quantity, conditional on the model and assumptions. Reporting an effect estimate with its interval generally gives more information about magnitude and precision than reporting a significance label alone. Neither an inferential estimate nor an interval for this primary comparison is reported in the registry record.

The registry indicates no analyses. The reason for this absence is not reported. The outcome summaries should not be used to infer an unreported p-value, interval, or model result. General statistical context: calculations based on summary statistics may be useful as clearly labeled, unadjusted recalculations when the underlying design and required data are suitable. But a simple unpaired recalculation would not represent the within-participant crossover analysis, and the paired data needed for that analysis are not posted. No recalculated treatment contrast is presented in the record.

What can planning calculations tell readers?

General statistical context: sample-size planning calculations describe how many participants might be needed under stated assumptions to detect a chosen effect with a chosen power and significance level. A planning illustration based on an observed effect is not the trial's original design justification and is not observed power. Observed power is not a substitute for an effect estimate and its confidence interval. The record does not report the trial's own sample-size justification, and the planning assumptions do not establish that the study was designed to detect a particular clinically meaningful contrast. Any sample-size illustration should therefore be interpreted as conditional planning information, not as evidence about the observed treatment effect.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("G6PD Deficient Red Blood Cell Transfusion", "Non-G6PD Deficient Red Blood Cell Transfusion")
n   <- c(3, 5)
m   <- c(82.91, 91.03)
sp  <- c(5.57, 3.9)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  G6PD Deficient Red Blood Cell Transfusion  3  82.910  5.570  69.073  96.747
CARM  Non-G6PD Deficient Red Blood Cell Transfusion  5  91.030  3.900  86.188  95.872

11. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary endpoint as percentage of red blood cells surviving and lists mean percent change in Hemoglobin A as a secondary outcome. It indicates two outcome measures, but no analyses are reported. Numerical results for the secondary outcome are not reported in the registry record. The record does not describe a prespecified hierarchy of outcomes, an adjustment for multiple testing, or a plan for interpreting findings across outcomes.

General statistical context: when several outcomes or comparisons are tested, the chance of a false-positive result can increase if each is assessed without accounting for the others. Multiplicity strategies can define one primary outcome, establish a testing order, or adjust inference across a family of tests. Without a reported statistical plan, it is not possible to tell whether or how multiplicity was considered. The presence of a listed primary and secondary outcome does not itself establish a particular adjustment method.

The registry does not report missing-data methods, an analysis population, or participant flow. It is not stated whether the primary outcome was available for every participant in both periods, how incomplete crossover participation was handled, or whether any observations were excluded. The group summary counts are n=3 and n=5, while total enrollment is 8; the record does not explain the relationship between those counts and the randomized sequences. No assumptions about the reason for the counts or the missingness mechanism can be made.

General statistical context: in a crossover trial, missing one period can prevent use of a participant's paired contrast, and the consequences depend on why data are missing and on the analysis approach. Methods may rely on assumptions about the missing outcomes, so transparent reporting of exclusions and sensitivity analyses is important. These details, as well as intention-to-treat or per-protocol definitions, are not reported in the registry record. The resulting uncertainty limits interpretation of the posted descriptive summaries.

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 non-serious adverse event terms

The registry reports serious adverse events for both transfusion types. For G6PD-deficient transfusion, 3 participants were listed as at risk, 0 had a serious adverse event, and 0 deaths were reported. For non-G6PD-deficient transfusion, 5 participants were listed as at risk, 0 had a serious adverse event, and 0 deaths were reported. The record lists other adverse events affecting 2 participants in the G6PD-deficient group and 1 participant in the non-G6PD-deficient group. No serious adverse event terms are listed.

These figures are counts in a small study record, not proof that no safety events could occur. General statistical context: when no serious events are observed, the data still allow uncertainty about the underlying event risk, particularly when few participants are represented. The figures also do not establish a comparative safety effect. The registry does not report event timing, severity details beyond the serious-event classification, or an analysis comparing adverse-event rates.

The adverse-event group counts are presented by transfusion type, but the crossover design means participants may contribute under both conditions. The record does not explain whether events were attributed to a particular period, how repeated events were counted, or how the safety population was defined. The counts should therefore be read as the posted registry figures, without assuming that they represent independent groups or a formal safety comparison.

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

The registry record documents a small randomized crossover study asking whether early survival differs between red blood cells identified as G6PD-deficient and those identified as not G6PD-deficient. It reports the percentage surviving at 24 hours post-transfusion as a mean of 82.91 (standard deviation 5.57; n=3) for the deficient transfusion and 91.03 (standard deviation 3.9; n=5) for the non-deficient transfusion. These summaries describe the posted observations, but they do not provide a formal estimate of the within-participant contrast.

The record does not report a confidence interval, p-value, statistical model, or analysis population. It also does not include paired participant-level outcomes. As a result, the precision of the contrast and the extent to which the descriptive pattern reflects a consistent within-person difference cannot be assessed from the registry record. No numerical result for the listed secondary outcome is reported.

General statistical context: an observed difference between group means is not, by itself, proof of a treatment effect. Interpretation depends on the study design, outcome completeness, analysis choices, and uncertainty around the effect estimate. In a crossover study, the pairing and period structure matter. Without the relevant analysis and data, the posted summaries cannot answer whether the observed pattern is statistically distinguishable from random variation under an appropriate model.

The record also does not establish an effect on longer-term red-cell lifespan, clinical outcomes, or safety beyond the adverse-event counts described. The primary measurement is specific to 24 hours post-transfusion. The terminated status and lack of reported analysis details further limit what can be concluded, but the reason for termination is not reported. The appropriate interpretation is therefore descriptive: the registry contains group summaries and adverse-event counts, not a reported inferential conclusion about comparative efficacy or safety.

14. Why This Trial Matters Statistically

This study raises a statistical question that is particularly visible in crossover research: whether a treatment comparison should be based on separate group summaries or on paired outcomes from the same participants. The sequence descriptions indicate that participants were assigned to receive both transfusion types in different orders. That structure can make within-person contrasts informative, but only if the paired measurements and the analysis are reported. The posted arm-level means do not show those contrasts.

The record also illustrates the difference between a descriptive result and an inferential result. Means and standard deviations tell readers about the observed group summaries and spread. A formal treatment contrast with an uncertainty interval would address the magnitude and precision of the comparison more directly. Here, no such analysis is reported. This distinction is important because a visible difference between means does not by itself establish how reliably that difference would be estimated.

Small enrollment, crossover participation, and missing analysis details make transparent reporting especially important. Readers need to know who contributed data in each period, how incomplete sequences were handled, whether period and sequence were included in the model, and how the primary contrast was estimated. The registry does not report these details, so they cannot be reconstructed from the summaries alone.

Finally, the record makes clear why outcome and safety findings should be kept within their measured scope. Red-cell survival is reported at 24 hours post-transfusion; it is not a longer-term clinical endpoint. The serious-event counts are descriptive and do not constitute a powered comparative safety analysis. Clear separation of endpoint, design, and inferential evidence helps readers avoid treating a biological measure or a sparse event count as a broader clinical conclusion.

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.

Several trial-specific limitations affect interpretation. Enrollment is listed as 8 and the study status as terminated, but the reason for termination and whether recruitment or follow-up ended as planned are not reported in the registry record. The arm summaries include n=3 for G6PD-deficient transfusion and n=5 for non-G6PD-deficient transfusion; the record does not explain how these counts relate to participants assigned to each crossover sequence or whether all participants contributed an outcome in both periods.

The primary results are descriptive means and standard deviations. A paired treatment contrast, confidence interval, p-value, analysis method, and participant-level data are not reported. The registry indicates no analyses. It is therefore not possible to assess the statistical uncertainty of the treatment comparison, determine whether the crossover structure was incorporated, or understand how incomplete observations may have been handled.

The record does not report the sample-size justification, missing-data approach, analysis-population definitions, or multiplicity strategy. It also does not explain the rationale for the 4-month interval or describe handling of period, sequence, and carryover effects. The identity of the masked party, allocation procedures, and details of the local laboratory procedures used to identify G6PD status are not reported. These gaps limit assessment of design implementation and potential sources of bias.

The primary outcome concerns red-cell survival at 24 hours post-transfusion. The listed secondary outcome, mean percent change in Hemoglobin A, has no numerical result reported in the registry record. Safety counts are available, but the record does not describe event timing, repeated-event handling, or a formal comparison. These limitations mean that the posted findings should be treated as descriptive and confined to the specific outcomes and timeframe recorded.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Impact of Oxidative Stress on Erythrocyte Biology — NCT04028700.
• Registry record last updated 2025-06-03; status last verified 2025-05.
• Results first posted 2025-06-03.
• 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

The registry record describes a randomized, single-masked, crossover Phase 2 study of G6PD-deficient and non-G6PD-deficient red blood cell transfusions in people with sickle cell disease without crisis. It lists enrollment of 8, study status as terminated, a start date of 2022-01-02, and a primary completion date of 2024-07-18. The reason for termination is not reported in the registry record.

The primary outcome is the percentage of red blood cells surviving at 24 hours post-transfusion. The posted mean is 82.91 (standard deviation 5.57; n=3) for G6PD-deficient transfusion and 91.03 (standard deviation 3.9; n=5) for non-G6PD-deficient transfusion. No formal analysis is reported. The record lists mean percent change in Hemoglobin A as a secondary outcome, without a numerical result. Serious adverse events and deaths are listed as 0 in both groups; other adverse events affected 2 participants in the deficient group and 1 in the non-deficient group.

Interpretation is limited by the absence of a reported crossover contrast, uncertainty interval, analysis population, and details on missing outcomes and analysis methods. The record supports descriptive reporting, not a formal conclusion about comparative treatment effects.