Inhaled Nitric Oxide and Neuroprotection in Premature Infants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Inhaled Nitric Oxide and Neuroprotection in Premature Infants (NCT00515281), a randomized phase 2, phase 3 study. The primary outcome is Neurodevelopment.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group study with quadruple masking and Phase 2 and Phase 3 designations. Enrollment was 273, and the sponsor was the University of Chicago. The study began in 2008-05, had a primary completion date of 2023-06-07, and is listed as terminated. These record details describe the study structure and status; they do not establish why the study was terminated beyond the primary outcome note that data were not collected due to funding cuts.

The two described arms differed in the duration of inhaled nitric oxide. The control arm, called INO Control (Short iNO), received iNO for the first 7 days of study gas, then oxygen or room air, as clinically appropriate, beginning on the 8th day and continuing until 33 weeks corrected age. The INO Treatment (Long iNO) arm received iNO combined with oxygen or room air until 33 weeks corrected age. The registry does not report more detailed dose, adherence, or treatment-separation information in the arm descriptions.

Randomization supports comparison of assigned groups in principle, while masking can reduce some risks of bias in trial conduct and outcome assessment. The record does not specify the randomization sequence, allocation concealment, which study roles were masked, or how masking was maintained. It also does not report the statistical plan or sample-size justification. The enrollment figure is not itself evidence that the trial was powered for its primary outcome.

The registry lists secondary outcomes including death, bronchopulmonary dysplasia, supplemental oxygen use, and combined BPD-or-death outcomes in specified subgroups. The primary neurodevelopment endpoint was intended for assessment at two years, but was not collected. The reported status is terminated; the registry record does not provide a completed primary outcome comparison.

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: Data were not collected (due to funding cuts).

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 Neurodevelopment, measured over Two years.

Neurodevelopment was the designated primary endpoint, with a timeframe of two years. In general, a neurodevelopment endpoint is intended to assess aspects of a child's developmental or neurological status beyond the immediate neonatal period. Such outcomes may address longer-term function that is not captured by short-term clinical events alone. That general rationale does not specify which domains or instruments were intended in this trial.

The registry does not identify a measurement instrument, scoring system, outcome categories, or analysis scale for neurodevelopment. Those details are not reported in the registry record. Most importantly, the registry explicitly states that the data were not collected because of funding cuts. There is therefore no posted primary endpoint estimate, group comparison, confidence interval, or statistical test to interpret.

Without collected endpoint data, it is not possible to judge the direction, magnitude, or precision of a treatment-group difference in neurodevelopment from the registry record. The planned two-year timing remains useful context for understanding what the study intended to evaluate, but it is not an observed result. The secondary outcomes cannot be treated as substitutes for the missing primary endpoint: they describe different outcomes and do not supply a neurodevelopment measurement.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record describes a randomized, parallel-group comparison, but does not report the statistical analysis plan. The primary outcome is neurodevelopment at two years, and the registry states that those data were not collected because of funding cuts. The discussion below explains relevant statistical ideas in general; it does not describe analyses that can be verified as having been performed for this trial.

What randomization contributes

In general, randomization assigns participants to groups using a chance-based process. When implemented as planned, it can balance measured and unmeasured baseline characteristics on average, reducing confounding in a comparison of assigned groups. The registry identifies the study as randomized but does not report the sequence-generation method, allocation concealment procedures, or details needed to evaluate implementation. Randomization does not guarantee identical groups in a particular trial, and it cannot prevent bias from missing outcomes, nonadherence, or analysis decisions made after assignment.

What the parallel comparison represents

A parallel-group design assigns participants to one group and compares outcomes across groups. Here the arm descriptions define a short- and a long-duration iNO schedule. The comparator is not described as no iNO throughout the study: the short-duration group received iNO for the first 7 days of study gas. This matters when interpreting the clinical contrast. It is a comparison of the assigned schedules in the record, not a direct contrast between any exposure and no exposure.

In general, the analysis approach should align with the study question. An intention-to-treat analysis compares groups according to original assignment, while a per-protocol approach focuses on participants who followed specified treatment procedures. The registry record does not state which analysis population was planned or used. It also does not report treatment adherence, crossover, or protocol-deviation details, so the effect of those factors cannot be assessed.

How to understand estimates and uncertainty

A group estimate describes an outcome in a group, while a comparative estimate expresses the contrast between groups. A confidence interval gives a range of values compatible with the data and the statistical procedure under its assumptions. Narrower intervals generally indicate greater precision; wider intervals indicate greater uncertainty. A confidence interval does not guarantee that the true value falls within its limits, and it does not resolve bias or limitations in the underlying data.

No primary neurodevelopment estimate or confidence interval is reported because the outcome data were not collected. The registry does not report a primary-outcome p-value either. A p-value, in general, describes how unusual data at least as incompatible with a specified null model would be under that model; it is not the probability that the null hypothesis is true and does not measure clinical importance. Without a reported endpoint analysis, a p-value cannot be interpreted for the primary question.

Why analysis details matter

Different outcome types may call for different statistical methods. A continuous score, a binary event, and time until an event do not have the same data structure. A count of events may also require methods that allow for over-dispersion, which occurs when observed variability exceeds that expected under a simpler count model. These are general considerations only. The record does not identify a model for neurodevelopment or specify an analysis method for the secondary outcomes.

The registry lists 8 outcome measures and 7 analyses, but does not give enough detail to map each analysis to a particular measure or determine which results were planned as confirmatory. The record also indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Without the outcome definitions, prespecified contrasts, and analysis plan, it is not possible to reconstruct a single primary statistical comparison.

Planning illustrations are not trial results

Any sample-size calculations associated with this analysis are planning illustrations based on an observed effect, not the trial's own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the illustration concerns the total number of events; for other outcomes, it concerns participants per arm. These calculations are not observed power and do not establish the original design assumptions. The registry record does not report the trial's sample-size justification or the observed primary effect needed to interpret an effect-based illustration.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study evaluates multiple outcomes, subgroups, time points, or statistical comparisons. In general, testing many hypotheses without an appropriate plan can increase the chance of at least one apparently noteworthy result arising by chance. Methods such as prespecified outcome hierarchies or adjusted significance thresholds can address some multiplicity concerns, but the suitable approach depends on the study question and analysis plan.

The registry lists 8 outcome measures and 7 analyses. It also lists secondary outcomes including death, bronchopulmonary dysplasia, supplemental oxygen use, and BPD or death in specified weight and race subgroups. The record does not describe how these outcomes and analyses were organized, whether subgroup comparisons were prespecified, or whether any multiplicity adjustment was planned or used. The number of measures and analyses alone does not establish how many independent tests were performed.

The primary outcome has several categories or time points and was not reduced to one comparison in the registry record. Neurodevelopment data were not collected because of funding cuts. The record does not describe any missing-data method, and it does not report analysis populations for the primary or secondary outcomes. Although the stated reason for the missing primary endpoint is given, the consequences for any planned analysis cannot be evaluated from the record.

In general, an analysis population should be clearly defined, and missing outcomes should be described alongside the assumptions used to handle them. The registry does not provide that information for the primary endpoint. No imputation strategy, sensitivity analysis, or treatment of incomplete observations is reported in the registry record. These gaps limit assessment of analysis choices and of the statistical evidence for the planned clinical question.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: symptomatic patent ductus arteriosis (pda) (32.6%), pulmonary interstitial emphysema (pie) (19.3%), necrotizing enterocolitis (nec) of bell's stage 2 severity or greater (14.1%), severe ivh/pvl (11.9%), pneumorthorax (9.4%).

The registry reports serious adverse event counts by arm. In the INO Control (Short iNO) group, 138 participants were listed as at risk and 53 as affected; 19 deaths were listed. In the INO Treatment (Long iNO) group, 135 participants were listed as at risk and 61 as affected; 13 deaths were listed. These figures describe the record's reported counts and are not, by themselves, a statistical comparison.

The registry also lists serious-event terms and percentages: symptomatic patent ductus arteriosis (PDA), 32.6%; pulmonary interstitial emphysema (PIE), 19.3%; necrotizing enterocolitis (NEC) of Bell's stage 2 severity or greater, 14.1%; severe IVH/PVL, 11.9%; pneumorthorax, 9.4%; and pulmonary hemorrhage, 3.7%. The denominator for these percentages and whether they refer to participants, events, or another basis are not reported in the registry record. They should not be interpreted as arm-specific rates.

The record does not say whether a participant could contribute more than one event or whether the deaths overlap with the serious-event counts. It also provides no uncertainty intervals or comparative statistical test for the safety figures. Descriptive counts should therefore be read as reported safety information, not as proof of a difference or as a causal estimate.

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

The registry record documents a randomized, quadruple-masked, parallel-group study comparing a short and a long duration of inhaled nitric oxide in premature infants. Its primary question concerned neurodevelopment at two years. The record states that neurodevelopment data were not collected because of funding cuts, so it does not answer that primary question. There is no posted primary endpoint estimate, confidence interval, or statistical test to interpret.

This missing result should not be confused with a finding of no difference. A lack of collected outcome data leaves the comparison unknown in the record; it does not show that the groups were equivalent or that either schedule changed neurodevelopment. Nor can the reported safety counts be used to infer a neurodevelopment effect. Those are distinct outcomes, and the registry does not report a statistical link between them.

The serious adverse event and death counts are descriptive. Without a reported comparative analysis, uncertainty estimates, and clearer details about event definitions and overlap, they cannot establish that one group had more or fewer events in a way attributable to its assigned treatment schedule. The term percentages also lack a stated denominator in the record.

More generally, the record does not provide enough information to assess the planned statistical analysis, missing-data handling, or analysis populations. It lists several secondary outcomes, but does not document a multiplicity strategy or a complete mapping of analyses to outcomes. These limitations constrain how much can be concluded from the posted information.

The appropriate statistical reading is therefore narrow: the study design and some safety counts are recorded, but the primary neurodevelopment outcome is unavailable and a primary comparative conclusion cannot be drawn from the registry record. This is a statement about the evidence recorded, not a medical recommendation or a claim about what the treatment would do.

13. Why This Trial Matters Statistically

This trial is statistically notable because its named primary outcome is absent from the registry results. A randomized design can support a strong comparison only when the relevant outcomes are measured and analyzed. Here, the record says neurodevelopment at two years was not collected because of funding cuts. That makes the distinction between a planned endpoint and an observed endpoint especially important: a protocol question can remain unanswered even when the study design is randomized and masked.

The record also illustrates why outcome timing and outcome type matter. The primary question concerned neurodevelopment at two years, while the listed secondary outcomes include neonatal or clinical events such as death, bronchopulmonary dysplasia, and supplemental oxygen use. These outcomes may be informative in their own right, but they do not measure the same construct as neurodevelopment. Substituting one for another would change the question being answered.

Its safety reporting also demonstrates the value of denominator and analysis details. Counts, at-risk figures, deaths, and event-term percentages each describe different aspects of safety information. Without clear definitions and comparative uncertainty estimates, they should remain descriptive rather than being promoted as a definitive between-group effect.

Finally, the registry lists multiple outcome measures and analyses but does not report the statistical plan, analysis populations, or multiplicity approach. This makes transparent reporting of prespecified contrasts and missing-data decisions important for interpreting trial records generally. In this study, the available record supports a careful account of design and reported safety information, while leaving the central neurodevelopment comparison unresolved.

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 most important trial-specific limitation is the missing primary outcome. Neurodevelopment was designated for assessment at two years, but the registry says data were not collected because of funding cuts. No endpoint definition, instrument, group estimate, or analysis is reported. The primary clinical question therefore cannot be evaluated from the posted results.

The registry lists the study as terminated, but gives no further account of the termination beyond the funding-related note about missing neurodevelopment data. It does not report how funding cuts affected secondary outcome collection, follow-up, or the planned analysis. Those details are not reported in the registry record.

Although the study is described as randomized and quadruple-masked, the record does not specify sequence generation, allocation concealment, which roles were masked, or how masking was maintained. It also does not report baseline characteristics, adherence, crossover, or protocol deviations in the information. These omissions limit assessment of trial conduct and the comparability of groups as actually treated.

The record does not report a statistical analysis plan, sample-size justification, primary analysis population, missing-data procedure, or multiplicity strategy. It lists 8 outcome measures and 7 analyses, but does not establish a complete mapping between them. As a result, the prespecification and interpretation of secondary comparisons cannot be assessed.

Safety reporting is also limited in interpretability. The registry gives arm-specific serious adverse event and death counts, and lists serious-event terms with percentages, but does not state the denominator for those percentages or whether events overlap within participants. Comparative estimates and uncertainty intervals are not reported. These limitations mean the counts should be treated as descriptive registry information rather than as a complete comparative safety analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Inhaled Nitric Oxide and Neuroprotection in Premature Infants — NCT00515281.
• Registry record last updated 2024-10-17; status last verified 2024-07.
• Results first posted 2024-10-17.
• 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

NCT00515281, Inhaled Nitric Oxide and Neuroprotection in Premature Infants, is listed as a randomized, quadruple-masked, parallel Phase 2 and Phase 3 study sponsored by the University of Chicago. Enrollment was 273. The registry lists a start of 2008-05, primary completion on 2023-06-07, and status as terminated.

The study compared a short iNO schedule with a longer schedule extending until 33 weeks corrected age. Neurodevelopment at two years was the primary outcome, but those data were not collected because of funding cuts. The record lists 8 outcome measures and 7 analyses, along with secondary outcomes covering death, bronchopulmonary dysplasia, supplemental oxygen use, and specified BPD-or-death subgroups.

Serious adverse event counts and deaths are reported for both groups, along with serious-event terms and percentages whose denominator is not stated. The registry record does not provide a primary neurodevelopment estimate or enough statistical detail to draw a comparative conclusion about that outcome.