Pilot Study About the Harmful Effects of Blood Storage on Overweight People and the Role of iNO in This Setting: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pilot Study About the Harmful Effects of Blood Storage on Overweight People and the Role of iNO in This Setting (NCT01529502), a randomized phase 2 study. The primary outcome is Systolic Pulmonary Artery Pressure.

2. Clinical Question

3. Trial Design

This phase 2 study is listed as randomized, single-masked, and crossover, with enrollment of 14. It was sponsored by Massachusetts General Hospital. The registry record gives a start date of 2012-03, a primary completion date of 2013-12, and a completed status. Its title identifies overweight subjects with endothelial dysfunction, and the brief summary describes autologous blood transfusion: participants donate blood and later receive the same blood back.

The listed conditions are Fresh Blood, Old Blood, and Old Blood + Inhaled Nitric Oxide. The listed interventions include red blood cell autotransfusion and inhaled nitric oxide administration. The record does not describe the procedures in enough detail to establish the exact storage intervals, the dose or timing of iNO, or how each condition was implemented. Those details are not reported in the registry record.

A crossover design means that participants can receive more than one study condition, so observations under different conditions may come from the same person. This structure can make within-participant comparisons relevant, but the registry record does not report the treatment sequence, number of periods, washout interval, or handling of possible carryover effects. It also does not identify which party was masked. Randomization and masking are recorded as design features, but their implementation is not described.

The primary endpoint is systolic pulmonary artery pressure after transfusion, estimated by transthoracic echocardiography. The record also names endothelial function measured by Reactive Hyperemia Index as a secondary outcome. It reports nine outcome measures overall, but the full set of measure descriptions and their analysis details are not included in the available record. No statistical analysis results are posted.

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: In the "fresh blood" only 9 volunteers estimation of Systolic Pulmonary Artery Pressure was successfully studied by trans-thoracic echocardiography. In the "old blood" only 11 volunteers and In the "old blood + Inhaled Nitric Oxide" only 12 volunteers estimation of Systolic Pulmonary Artery Pressure was successfully evaluated.

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Systolic Pulmonary Artery Pressure, measured over Post-transfusion.

The primary endpoint is systolic pulmonary artery pressure, measured after transfusion and expressed in mmHg. The registry describes pulmonary vasoconstriction as being assessed by estimating this pressure with transthoracic echocardiography. In general, pulmonary artery pressure is used as a physiological measure relevant to vascular constriction in the pulmonary circulation. The endpoint therefore addresses a physiological response to transfusion rather than a patient-centered clinical outcome such as symptoms or survival.

The record reports means with standard errors. The posted mean was 39 mmHg (standard error 3) after fresh blood, 46 mmHg (standard error 3) after old blood, and 31 mmHg (standard error 2) after old blood with inhaled nitric oxide. The corresponding endpoint sample sizes were 9, 11, and 12. These are the numbers of volunteers for whom the endpoint was successfully studied in each condition, according to the registry description.

In general, a mean describes the average measured value in a group, while the standard error describes the precision of that estimated mean. The standard error is not a measure of the full spread of individual participant measurements. No confidence intervals or inferential analyses are posted, so the means and standard errors alone do not establish the precision of contrasts between conditions. The registry record does not report a threshold for a clinically important change in pressure.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted outcome summaries are means and standard errors for a continuous endpoint. The mean is the arithmetic average of measured systolic pulmonary artery pressure values within a condition. The standard error quantifies uncertainty in the estimated mean under the assumptions of the method used. In general, it is distinct from a standard deviation, which describes variation among individual measurements. The registry labels the reported dispersion as standard error, not standard deviation.

What do the group summaries say?

The means are 39 mmHg for fresh blood, 46 mmHg for old blood, and 31 mmHg for old blood with inhaled nitric oxide. Their reported standard errors are 3, 3, and 2. The endpoint counts are 9, 11, and 12, respectively. These summaries allow readers to describe the values and the stated precision of each mean. They do not provide the distribution of individual measurements, and they do not directly quantify uncertainty in a comparison between conditions.

In general, a confidence interval gives a range of values compatible with data and a stated statistical procedure. No confidence interval is posted for these means or for contrasts. Without intervals or a comparison analysis, the standard errors for separate group means should not be treated as a substitute for an interval around a difference. No new contrast or uncertainty estimate is calculated from the posted summaries.

Why does the crossover design matter?

In general, a crossover trial exposes participants to multiple conditions, so measurements from the same participant may be correlated. A paired or otherwise repeated-measures analysis can use that relationship and account for within-person variation. By contrast, treating every condition observation as independent may fail to represent the design. The registry record does not report the analysis model, whether comparisons used paired measurements, or how repeated measures were handled. It also does not report the condition sequence, washout, or assessment of period and carryover effects. Thus, the appropriate structure of the analysis cannot be verified from the posted group summaries.

The endpoint counts vary across conditions. The record says pressure estimation was successfully studied in 9 volunteers under fresh blood, 11 under old blood, and 12 under old blood plus iNO. A crossover design means these counts should not automatically be read as separate groups of unique people. The record does not identify which participants contributed to multiple conditions, why endpoint measurements were unavailable, or whether missing measurements were related to participant or study characteristics.

What inferential results are available?

The registry record lists no analyses. It does not post an estimated treatment contrast, standard error for a contrast, confidence interval, test statistic, or p-value. There is therefore no posted inferential result with which to assess whether the condition means are statistically distinguishable. The absence of a reported analysis is not evidence that conditions are equivalent; it means the registry record does not give a result that can establish either a difference or equivalence.

In general, an analysis plan specifies the outcome model, comparison, assumptions, handling of repeated observations, and treatment of missing data. These details matter because they determine what quantity an estimate represents and how its uncertainty is calculated. The analysis plan, model specification, and any adjustment strategy are not reported in the registry record. No sample-size justification or interim-analysis plan is reported there either. The enrollment count is not a substitute for those design details.

How should precision be understood?

The standard errors describe estimated means, not the full uncertainty around an unreported comparison. In general, precision depends on the amount of information in the data and the variability and dependence structure of measurements. In a crossover study, within-person correlation can influence the precision of paired contrasts. Because the record gives neither participant-level values nor contrast estimates, that correlation and the precision of the comparisons cannot be reconstructed from the posted information.

In general, over-dispersion means that observed variability is greater than a model assumes. When that occurs, model-based standard errors can be too small unless the analysis accommodates the extra variability. The registry record does not report a fitted model or diagnostics, so there is no basis for assessing over-dispersion in these endpoint data. This is a general statistical consideration, not a claim that over-dispersion occurred in this study.

There are no recalculated estimates posted for this endpoint. Any planning illustration based on an observed effect would be a design exercise, not observed power or evidence that the trial was adequately powered. The registry record does not report a sample-size justification. Overall, the means and standard errors provide descriptive information, while the inferential and design details needed to evaluate comparative precision remain unreported.

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("Fresh Blood", "Old Blood", "Old Blood + Inhaled Nitric Oxide")
n   <- c(9, 11, 12)
m   <- c(39, 46, 31)
sp  <- c(3, 3, 2)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Fresh Blood  9  39.000  9.000  32.082  45.918
CARM  Old Blood  11  46.000  9.950  39.316  52.684
CARM  Old Blood + Inhaled Nitric Oxide  12  31.000  6.928  26.598  35.402

11. Multiplicity, Missing Data and Analysis Populations

The registry record reports nine outcome measures and identifies Reactive Hyperemia Index, a measure of endothelial function, as a secondary outcome. It does not provide the full list of outcome measures in the registry record used for this analysis, and it reports no analyses. The primary endpoint is systolic pulmonary artery pressure. No multiplicity adjustment, prespecified testing hierarchy, or strategy for interpreting several outcomes is reported in the registry record.

In general, when several outcomes or comparisons are examined, the chance of obtaining an apparently notable result by chance can increase. A prespecified hierarchy or adjustment can help define how to interpret multiple tests. Since no inferential analyses are posted, there are no reported p-values to assess for multiplicity, and there is no basis for determining whether an adjustment was applied. The record also does not say whether all nine outcome measures were planned in advance or how secondary outcomes were treated.

For the primary endpoint, the record reports different numbers of successful measurements by condition: 9, 11, and 12. These counts indicate that endpoint data were not available for every enrolled participant in every listed condition, but do not identify the reason. In a crossover study, they also do not establish the number of unique participants contributing to each comparison. The record does not describe missing-data assumptions, imputation, sensitivity analyses, or whether incomplete condition sequences were included.

The analysis populations are not reported in the registry record. It is therefore unclear whether the posted summaries represent all participants with available endpoint measurements, a prespecified analysis population, or another selection. Without those details, readers cannot assess how missing observations or population definitions might affect the condition comparisons.

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.

The registry lists serious adverse events, other adverse events, and deaths by condition. For Fresh Blood, 0 serious events were reported among 14 at risk, 0 other events among 14 at risk, and 0 deaths. For Old Blood, 0 serious events were reported among 13 at risk, 0 other events among 13 at risk, and 0 deaths. For Old Blood + Inhaled Nitric Oxide, 0 serious events were reported among 12 at risk, 0 other events among 12 at risk, and 0 deaths.

These are registry counts for the listed groups and their stated numbers at risk. They should be read as reported event counts, not as proof that an event was impossible or that the conditions have no safety risks. The at-risk counts differ across conditions, and the record does not explain the difference or give details about how safety follow-up was conducted. It also does not provide event timing, duration of follow-up, severity classifications beyond the serious-versus-other categories, or a fuller description of ascertainment.

The record lists no serious adverse event terms. Zero reported events in these groups is a descriptive safety finding for the registry record; it does not establish comparative safety or rule out uncommon harms.

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

The results establish what was posted for the primary physiological endpoint: mean systolic pulmonary artery pressure after transfusion was 39 mmHg for fresh blood, 46 mmHg for old blood, and 31 mmHg for old blood with inhaled nitric oxide. The associated standard errors were 3, 3, and 2, and the endpoint counts were 9, 11, and 12. These values permit a descriptive account of the observed condition summaries.

They do not establish whether storage time caused a change in pressure, whether iNO altered a response to old blood, or whether any contrast was statistically distinguishable. The record does not post inferential analyses, confidence intervals, p-values, or adjusted comparisons. Because the study is crossover, interpretation of contrasts depends on how within-participant measurements and study periods were handled; that analysis is not reported.

The endpoint is a post-transfusion physiological measure, not a direct assessment of symptoms or long-term clinical outcomes. The record does not state a threshold for a clinically important pressure change. Consequently, the posted summaries alone do not indicate the clinical importance of the observed values. They also do not demonstrate that one condition is clinically preferable to another.

The listed secondary outcome is Reactive Hyperemia Index, but its results are not reported in the registry record. The record lists nine outcome measures and no analyses. The available information is therefore limited to the primary endpoint summaries and the registry’s adverse-event counts. It cannot support broad conclusions about endothelial function, patient benefit, or safety beyond those descriptions.

In general, a small pilot study can help characterize feasibility and generate questions for further investigation, but its observed summaries should not be confused with a definitive comparative estimate. The registry record does not report a sample-size justification or analysis plan, so the intended precision and the planned approach to the crossover data are unknown. These limitations leave the comparative meaning of the means unresolved.

14. Why This Trial Matters Statistically

This trial raises a statistical question that is easy to overlook when reading group averages: the observations come from a randomized crossover design, not necessarily from independent sets of participants in each condition. In general, repeated measurements from the same participant are related. A comparison that accounts for that relationship can have a different uncertainty from one that treats measurements as independent. The registry record does not describe how that feature was handled, making the design and analysis alignment difficult to assess.

The condition-specific endpoint counts also differ: 9 for fresh blood, 11 for old blood, and 12 for old blood with inhaled nitric oxide. This variation matters because the group means may be based on different sets of observed condition measurements. The record does not state why measurements were unavailable or how missing endpoint data were treated. It also does not provide individual records needed to understand overlap between conditions.

Another important distinction is between descriptive results and comparative evidence. The means and standard errors are useful summaries, but without a reported contrast and its uncertainty they cannot answer whether the conditions differ beyond sampling variation. The registry’s absence of analyses does not imply that the means are equal, nor does it establish a difference. It leaves the inferential question unanswered in the posted record.

The study also highlights the need to distinguish a physiological endpoint from a clinical outcome. Systolic pulmonary artery pressure is the primary measure, while Reactive Hyperemia Index is named as a secondary outcome. The record does not give a clinical-importance threshold or results for the secondary outcome. Interpreting the values therefore requires attention to what was measured and what was not reported, rather than extrapolation to broader clinical effects.

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.

The main limitation for statistical interpretation is that the registry record posts group means and standard errors but no analysis results. No treatment contrasts, confidence intervals, p-values, or model details are reported. This prevents assessment of comparative uncertainty and prevents verification that the analysis accounted for the crossover structure.

Several design details relevant to crossover analysis are not reported in the registry record: treatment order, period structure, washout, carryover assessment, and the handling of repeated measurements. The record identifies the trial as randomized and single-masked but does not describe the randomization procedure or state who was masked. These omissions limit the ability to evaluate implementation and potential sources of bias.

Endpoint counts vary across conditions, with successful pressure estimation reported for 9, 11, and 12 volunteers. The record does not explain why some measurements were unavailable, identify participants with complete or incomplete condition data, or report a missing-data strategy. Analysis populations are also not specified. With aggregate summaries alone, the effect of these features cannot be evaluated.

The registry does not report the full list of nine outcome measures, a multiplicity strategy, or the results for the named secondary outcome, Reactive Hyperemia Index. A sample-size justification, statistical analysis plan, and interim-analysis details are not reported in the registry record. No clinically important threshold is given for the primary endpoint. Finally, the safety counts are presented without detailed follow-up or event-ascertainment information. These limitations constrain interpretation to the posted descriptive summaries and event counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pilot Study About the Harmful Effects of Blood Storage on Overweight People and the Role of iNO in This Setting — NCT01529502.
• Registry record last updated 2017-05-22; status last verified 2017-04.
• Results first posted 2017-03-29.
• 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

NCT01529502 is a completed phase 2 randomized, single-masked crossover study sponsored by Massachusetts General Hospital. The registry lists enrollment of 14, a start date of 2012-03, and a primary completion date of 2013-12. The study concerns autologous red blood cell transfusion in overweight subjects with endothelial dysfunction, comparing fresh blood, old blood, and old blood with inhaled nitric oxide.

The primary endpoint is post-transfusion systolic pulmonary artery pressure in mmHg. Reported means were 39, 46, and 31, with standard errors of 3, 3, and 2, respectively. Endpoint counts were 9, 11, and 12. Reactive Hyperemia Index is listed as a secondary outcome. No statistical analyses are posted. The registry reports zero serious adverse events, zero other adverse events, and zero deaths in each listed condition group.